DVX_GUI/dvx/dvxApp.c

// dvx_app.c — Layer 5: Application API for DV/X GUI

#include "dvxApp.h"
#include "dvxWidget.h"
#include "widgets/widgetInternal.h"
#include "dvxFont.h"
#include "dvxCursor.h"

#include <string.h>
#include <ctype.h>
#include <time.h>
#include <dpmi.h>
#include <signal.h>

#define DBLCLICK_THRESHOLD     (CLOCKS_PER_SEC / 2)
#define ICON_REFRESH_INTERVAL  8
#define KB_MOVE_STEP           8
#define MENU_CHECK_WIDTH       14
#define SUBMENU_ARROW_WIDTH    12
#define TOOLTIP_DELAY_MS       500
#define TOOLTIP_PAD            3

// ============================================================
// Prototypes
// ============================================================

static void calcPopupSize(const AppContextT *ctx, const MenuT *menu, int32_t *pw, int32_t *ph);
static bool checkAccelTable(AppContextT *ctx, WindowT *win, int32_t key, int32_t modifiers);
static void clickMenuCheckRadio(MenuT *menu, int32_t itemIdx);
static void closeAllPopups(AppContextT *ctx);
static void closePopupLevel(AppContextT *ctx);
static void closeSysMenu(AppContextT *ctx);
static void compositeAndFlush(AppContextT *ctx);
static void dirtyCursorArea(AppContextT *ctx, int32_t x, int32_t y);
static bool dispatchAccelKey(AppContextT *ctx, char key);
static void dispatchEvents(AppContextT *ctx);
static void drawCursorAt(AppContextT *ctx, int32_t x, int32_t y);
static void drawPopupLevel(AppContextT *ctx, DisplayT *d, const BlitOpsT *ops, const MenuT *menu, int32_t px, int32_t py, int32_t pw, int32_t ph, int32_t hoverItem, const RectT *clipTo);
static void executeSysMenuCmd(AppContextT *ctx, int32_t cmd);
static WindowT *findWindowById(AppContextT *ctx, int32_t id);
static void handleMouseButton(AppContextT *ctx, int32_t mx, int32_t my, int32_t buttons);
static void initColorScheme(AppContextT *ctx);
static void initMouse(AppContextT *ctx);
static void openContextMenu(AppContextT *ctx, WindowT *win, MenuT *menu, int32_t screenX, int32_t screenY);
static void openPopupAtMenu(AppContextT *ctx, WindowT *win, int32_t menuIdx);
static void openSubMenu(AppContextT *ctx);
static void openSysMenu(AppContextT *ctx, WindowT *win);
static void pollAnsiTermWidgets(AppContextT *ctx);
static void pollAnsiTermWidgetsWalk(AppContextT *ctx, WidgetT *w, WindowT *win);
static void pollKeyboard(AppContextT *ctx);
static void pollMouse(AppContextT *ctx);
static void refreshMinimizedIcons(AppContextT *ctx);
static void updateCursorShape(AppContextT *ctx);
static void updateTooltip(AppContextT *ctx);

// Button pressed via keyboard — shared with widgetEvent.c for Space/Enter
WidgetT *sKeyPressedBtn = NULL;

// Alt+key scan code to ASCII lookup table (indexed by scan code)
// BIOS INT 16h returns these scan codes with ascii=0 for Alt+key combos
static const char sAltScanToAscii[256] = {
    // Alt+letters
    [0x10] = 'q', [0x11] = 'w', [0x12] = 'e', [0x13] = 'r',
    [0x14] = 't', [0x15] = 'y', [0x16] = 'u', [0x17] = 'i',
    [0x18] = 'o', [0x19] = 'p', [0x1E] = 'a', [0x1F] = 's',
    [0x20] = 'd', [0x21] = 'f', [0x22] = 'g', [0x23] = 'h',
    [0x24] = 'j', [0x25] = 'k', [0x26] = 'l', [0x2C] = 'z',
    [0x2D] = 'x', [0x2E] = 'c', [0x2F] = 'v', [0x30] = 'b',
    [0x31] = 'n', [0x32] = 'm',
    // Alt+digits
    [0x78] = '1', [0x79] = '2', [0x7A] = '3', [0x7B] = '4',
    [0x7C] = '5', [0x7D] = '6', [0x7E] = '7', [0x7F] = '8',
    [0x80] = '9', [0x81] = '0',
};


// ============================================================
// calcPopupSize — compute popup width and height for a menu
// ============================================================

static void calcPopupSize(const AppContextT *ctx, const MenuT *menu, int32_t *pw, int32_t *ph) {
    int32_t maxW     = 0;
    bool    hasSub   = false;
    bool    hasCheck = false;

    for (int32_t k = 0; k < menu->itemCount; k++) {
        int32_t itemW = textWidthAccel(&ctx->font, menu->items[k].label);

        if (itemW > maxW) {
            maxW = itemW;
        }

        if (menu->items[k].subMenu) {
            hasSub = true;
        }

        if (menu->items[k].type == MenuItemCheckE || menu->items[k].type == MenuItemRadioE) {
            hasCheck = true;
        }
    }

    *pw = maxW + CHROME_TITLE_PAD * 2 + 8 + (hasSub ? SUBMENU_ARROW_WIDTH : 0) + (hasCheck ? MENU_CHECK_WIDTH : 0);
    *ph = menu->itemCount * ctx->font.charHeight + 4;
}


// ============================================================
// checkAccelTable — test key against window's accelerator table
// ============================================================

static bool checkAccelTable(AppContextT *ctx, WindowT *win, int32_t key, int32_t modifiers) {
    if (!win->accelTable || !win->onMenu) {
        return false;
    }

    // Normalize Ctrl+letter: BIOS returns ASCII 0x01-0x1A for Ctrl+A..Z
    // Map back to uppercase letter for matching
    int32_t matchKey = key;

    if ((modifiers & ACCEL_CTRL) && matchKey >= 0x01 && matchKey <= 0x1A) {
        matchKey = matchKey + 'A' - 1;
    }

    // Uppercase for case-insensitive letter matching
    if (matchKey >= 'a' && matchKey <= 'z') {
        matchKey = matchKey - 32;
    }

    int32_t      requiredMods = modifiers & (ACCEL_CTRL | ACCEL_ALT);
    AccelTableT *table        = win->accelTable;

    for (int32_t i = 0; i < table->count; i++) {
        AccelEntryT *e = &table->entries[i];

        // Uppercase the entry key too
        int32_t entryKey = e->key;

        if (entryKey >= 'a' && entryKey <= 'z') {
            entryKey = entryKey - 32;
        }

        int32_t entryMods = e->modifiers & (ACCEL_CTRL | ACCEL_ALT);

        if (entryKey == matchKey && entryMods == requiredMods) {
            win->onMenu(win, e->cmdId);
            return true;
        }
    }

    (void)ctx;
    return false;
}


// ============================================================
// clickMenuCheckRadio — toggle check or select radio on click
// ============================================================

static void clickMenuCheckRadio(MenuT *menu, int32_t itemIdx) {
    MenuItemT *item = &menu->items[itemIdx];

    if (item->type == MenuItemCheckE) {
        item->checked = !item->checked;
    } else if (item->type == MenuItemRadioE) {
        // Uncheck all radio items in the same group (consecutive radio items)
        // Search backward to find group start
        int32_t groupStart = itemIdx;

        while (groupStart > 0 && menu->items[groupStart - 1].type == MenuItemRadioE) {
            groupStart--;
        }

        // Search forward to find group end
        int32_t groupEnd = itemIdx;

        while (groupEnd < menu->itemCount - 1 && menu->items[groupEnd + 1].type == MenuItemRadioE) {
            groupEnd++;
        }

        // Uncheck all in group, check the clicked one
        for (int32_t i = groupStart; i <= groupEnd; i++) {
            menu->items[i].checked = (i == itemIdx);
        }
    }
}


// ============================================================
// closeAllPopups — dirty all popup levels and deactivate
// ============================================================

static void closeAllPopups(AppContextT *ctx) {
    if (!ctx->popup.active) {
        return;
    }

    // Dirty current (deepest) level
    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                 ctx->popup.popupW, ctx->popup.popupH);

    // Dirty all parent levels
    for (int32_t i = 0; i < ctx->popup.depth; i++) {
        PopupLevelT *pl = &ctx->popup.parentStack[i];
        dirtyListAdd(&ctx->dirty, pl->popupX, pl->popupY, pl->popupW, pl->popupH);
    }

    ctx->popup.active = false;
    ctx->popup.depth  = 0;
}


// ============================================================
// closePopupLevel — close one submenu level (or deactivate if top)
// ============================================================

static void closePopupLevel(AppContextT *ctx) {
    if (!ctx->popup.active) {
        return;
    }

    // Dirty current level
    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                 ctx->popup.popupW, ctx->popup.popupH);

    if (ctx->popup.depth > 0) {
        // Pop parent
        ctx->popup.depth--;
        PopupLevelT *pl  = &ctx->popup.parentStack[ctx->popup.depth];
        ctx->popup.menu      = pl->menu;
        ctx->popup.menuIdx   = pl->menuIdx;
        ctx->popup.popupX    = pl->popupX;
        ctx->popup.popupY    = pl->popupY;
        ctx->popup.popupW    = pl->popupW;
        ctx->popup.popupH    = pl->popupH;
        ctx->popup.hoverItem = pl->hoverItem;
    } else {
        ctx->popup.active = false;
    }
}


// ============================================================
// closeSysMenu
// ============================================================

static void closeSysMenu(AppContextT *ctx) {
    if (ctx->sysMenu.active) {
        dirtyListAdd(&ctx->dirty, ctx->sysMenu.popupX, ctx->sysMenu.popupY,
                     ctx->sysMenu.popupW, ctx->sysMenu.popupH);
        ctx->sysMenu.active = false;
    }
}


// ============================================================
// compositeAndFlush
// ============================================================

static void compositeAndFlush(AppContextT *ctx) {
    DisplayT     *d   = &ctx->display;
    BlitOpsT     *ops = &ctx->blitOps;
    DirtyListT   *dl  = &ctx->dirty;
    WindowStackT *ws  = &ctx->stack;

    dirtyListMerge(dl);

    for (int32_t i = 0; i < dl->count; i++) {
        RectT *dr = &dl->rects[i];

        // Clip dirty rect to screen bounds
        if (dr->x < 0) { dr->w += dr->x; dr->x = 0; }
        if (dr->y < 0) { dr->h += dr->y; dr->y = 0; }
        if (dr->x + dr->w > d->width)  { dr->w = d->width - dr->x; }
        if (dr->y + dr->h > d->height) { dr->h = d->height - dr->y; }
        if (dr->w <= 0 || dr->h <= 0) { continue; }

        // Set clip rect to this dirty rect
        setClipRect(d, dr->x, dr->y, dr->w, dr->h);

        // 1. Draw desktop background
        rectFill(d, ops, dr->x, dr->y, dr->w, dr->h, ctx->colors.desktop);

        // 2. Draw minimized window icons (under all windows)
        wmDrawMinimizedIcons(d, ops, &ctx->colors, ws, dr);

        // 3. Walk window stack bottom-to-top
        for (int32_t j = 0; j < ws->count; j++) {
            WindowT *win = ws->windows[j];

            if (!win->visible || win->minimized) {
                continue;
            }

            // Check if window intersects this dirty rect
            RectT winRect = {win->x, win->y, win->w, win->h};
            RectT isect;

            if (!rectIntersect(dr, &winRect, &isect)) {
                continue;
            }

            wmDrawChrome(d, ops, &ctx->font, &ctx->colors, win, dr);
            wmDrawContent(d, ops, win, dr);
            if (win->vScroll || win->hScroll) {
                wmDrawScrollbars(d, ops, &ctx->colors, win, dr);
            }
        }

        // 4. Draw popup menu if active (all levels)
        if (ctx->popup.active) {
            // Draw parent levels first (bottom to top)
            for (int32_t lvl = 0; lvl < ctx->popup.depth; lvl++) {
                PopupLevelT *pl = &ctx->popup.parentStack[lvl];
                drawPopupLevel(ctx, d, ops, pl->menu, pl->popupX, pl->popupY, pl->popupW, pl->popupH, pl->hoverItem, dr);
            }

            // Draw current (deepest) level
            drawPopupLevel(ctx, d, ops, ctx->popup.menu, ctx->popup.popupX, ctx->popup.popupY, ctx->popup.popupW, ctx->popup.popupH, ctx->popup.hoverItem, dr);
        }

        // 4b. Draw system menu if active
        if (ctx->sysMenu.active) {
            RectT smRect = { ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH };
            RectT smIsect;

            if (rectIntersect(dr, &smRect, &smIsect)) {
                BevelStyleT smBevel;
                smBevel.highlight = ctx->colors.windowHighlight;
                smBevel.shadow    = ctx->colors.windowShadow;
                smBevel.face      = ctx->colors.menuBg;
                smBevel.width     = 2;
                drawBevel(d, ops, ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH, &smBevel);

                int32_t itemY = ctx->sysMenu.popupY + 2;

                for (int32_t k = 0; k < ctx->sysMenu.itemCount; k++) {
                    SysMenuItemT *item = &ctx->sysMenu.items[k];

                    if (item->separator) {
                        drawHLine(d, ops, ctx->sysMenu.popupX + 2, itemY + ctx->font.charHeight / 2, ctx->sysMenu.popupW - 4, ctx->colors.windowShadow);
                        itemY += ctx->font.charHeight;
                        continue;
                    }

                    uint32_t bg = ctx->colors.menuBg;
                    uint32_t fg = item->enabled ? ctx->colors.menuFg : ctx->colors.windowShadow;

                    if (k == ctx->sysMenu.hoverItem && item->enabled) {
                        bg = ctx->colors.menuHighlightBg;
                        fg = ctx->colors.menuHighlightFg;
                    }

                    rectFill(d, ops, ctx->sysMenu.popupX + 2, itemY, ctx->sysMenu.popupW - 4, ctx->font.charHeight, bg);
                    drawTextAccel(d, ops, &ctx->font, ctx->sysMenu.popupX + CHROME_TITLE_PAD + 2, itemY, item->label, fg, bg, true);

                    itemY += ctx->font.charHeight;
                }
            }
        }

        // 5. Draw tooltip
        if (ctx->tooltipText) {
            RectT ttRect = { ctx->tooltipX, ctx->tooltipY, ctx->tooltipW, ctx->tooltipH };
            RectT ttIsect;

            if (rectIntersect(dr, &ttRect, &ttIsect)) {
                rectFill(d, ops, ctx->tooltipX, ctx->tooltipY, ctx->tooltipW, ctx->tooltipH, ctx->colors.menuBg);
                drawHLine(d, ops, ctx->tooltipX, ctx->tooltipY, ctx->tooltipW, ctx->colors.contentFg);
                drawHLine(d, ops, ctx->tooltipX, ctx->tooltipY + ctx->tooltipH - 1, ctx->tooltipW, ctx->colors.contentFg);
                drawVLine(d, ops, ctx->tooltipX, ctx->tooltipY, ctx->tooltipH, ctx->colors.contentFg);
                drawVLine(d, ops, ctx->tooltipX + ctx->tooltipW - 1, ctx->tooltipY, ctx->tooltipH, ctx->colors.contentFg);
                drawText(d, ops, &ctx->font, ctx->tooltipX + TOOLTIP_PAD, ctx->tooltipY + TOOLTIP_PAD, ctx->tooltipText, ctx->colors.menuFg, ctx->colors.menuBg, true);
            }
        }

        // 6. Draw cursor
        drawCursorAt(ctx, ctx->mouseX, ctx->mouseY);

        // 6. Flush this dirty rect to LFB
        flushRect(d, dr);
    }

    resetClipRect(d);
    dirtyListClear(dl);
}


// ============================================================
// dirtyCursorArea
// ============================================================

static void dirtyCursorArea(AppContextT *ctx, int32_t x, int32_t y) {
    // Dirty the union of all cursor shapes at this position to handle shape changes
    // All cursors are 16x16 with hotspot at either (0,0) or (7,7), so worst case
    // covers from (x-7, y-7) to (x+15, y+15) = 23x23 area
    dirtyListAdd(&ctx->dirty, x - 7, y - 7, 23, 23);
}


// ============================================================
// dispatchAccelKey — route Alt+key to menu or widget
// ============================================================

static bool dispatchAccelKey(AppContextT *ctx, char key) {
    if (ctx->stack.focusedIdx < 0) {
        return false;
    }

    WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

    // Check menu bar first
    if (win->menuBar) {
        for (int32_t i = 0; i < win->menuBar->menuCount; i++) {
            if (win->menuBar->menus[i].accelKey == key) {
                openPopupAtMenu(ctx, win, i);
                return true;
            }
        }
    }

    // Check widget tree
    if (win->widgetRoot) {
        WidgetT *target = widgetFindByAccel(win->widgetRoot, key);

        if (target) {
            switch (target->type) {
                case WidgetButtonE:
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    sFocusedWidget = target;
                    target->focused = true;
                    target->as.button.pressed = true;
                    sKeyPressedBtn = target;
                    wgtInvalidate(target);
                    return true;

                case WidgetCheckboxE:
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    widgetCheckboxOnMouse(target, win->widgetRoot, 0, 0);
                    sFocusedWidget = target;
                    wgtInvalidate(target);
                    return true;

                case WidgetRadioE:
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    widgetRadioOnMouse(target, win->widgetRoot, 0, 0);
                    sFocusedWidget = target;
                    wgtInvalidate(target);
                    return true;

                case WidgetImageButtonE:
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    sFocusedWidget = target;
                    target->focused = true;
                    target->as.imageButton.pressed = true;
                    sKeyPressedBtn = target;
                    wgtInvalidate(target);
                    return true;

                case WidgetTabPageE:
                {
                    // Close any open dropdown/combobox popup
                    if (sOpenPopup) {
                        if (sOpenPopup->type == WidgetDropdownE) {
                            sOpenPopup->as.dropdown.open = false;
                        } else if (sOpenPopup->type == WidgetComboBoxE) {
                            sOpenPopup->as.comboBox.open = false;
                        }

                        sOpenPopup = NULL;
                    }

                    // Activate this tab in its parent TabControl
                    if (target->parent && target->parent->type == WidgetTabControlE) {
                        int32_t tabIdx = 0;

                        for (WidgetT *c = target->parent->firstChild; c; c = c->nextSibling) {
                            if (c == target) {
                                wgtTabControlSetActive(target->parent, tabIdx);
                                wgtInvalidate(win->widgetRoot);
                                break;
                            }

                            if (c->type == WidgetTabPageE) {
                                tabIdx++;
                            }
                        }
                    }

                    return true;
                }

                case WidgetDropdownE:
                    target->as.dropdown.open     = true;
                    target->as.dropdown.hoverIdx = target->as.dropdown.selectedIdx;
                    sOpenPopup = target;
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    sFocusedWidget = target;
                    target->focused = true;
                    wgtInvalidate(win->widgetRoot);
                    return true;

                case WidgetComboBoxE:
                    target->as.comboBox.open     = true;
                    target->as.comboBox.hoverIdx = target->as.comboBox.selectedIdx;
                    sOpenPopup = target;
                    if (sFocusedWidget) { sFocusedWidget->focused = false; }
                    sFocusedWidget = target;
                    target->focused = true;
                    wgtInvalidate(win->widgetRoot);
                    return true;

                case WidgetLabelE:
                case WidgetFrameE:
                {
                    // Focus the next focusable widget
                    WidgetT *next = widgetFindNextFocusable(win->widgetRoot, target);

                    if (next) {
                        if (sFocusedWidget) { sFocusedWidget->focused = false; }
                        sFocusedWidget = next;
                        next->focused = true;

                        // Open dropdown/combobox if that's the focused target
                        if (next->type == WidgetDropdownE) {
                            next->as.dropdown.open     = true;
                            next->as.dropdown.hoverIdx = next->as.dropdown.selectedIdx;
                            sOpenPopup = next;
                        } else if (next->type == WidgetComboBoxE) {
                            next->as.comboBox.open     = true;
                            next->as.comboBox.hoverIdx = next->as.comboBox.selectedIdx;
                            sOpenPopup = next;
                        }

                        wgtInvalidate(win->widgetRoot);
                    }

                    return true;
                }

                default:
                    // For focusable widgets, just focus them
                    if (widgetIsFocusable(target->type)) {
                        if (sFocusedWidget) { sFocusedWidget->focused = false; }
                        sFocusedWidget = target;
                        target->focused = true;
                        wgtInvalidate(win->widgetRoot);
                        return true;
                    }
                    break;
            }
        }
    }

    return false;
}


// ============================================================
// dispatchEvents
// ============================================================

static void dispatchEvents(AppContextT *ctx) {
    int32_t mx      = ctx->mouseX;
    int32_t my      = ctx->mouseY;
    int32_t buttons = ctx->mouseButtons;
    int32_t prevBtn = ctx->prevMouseButtons;

    // Mouse movement always dirties old and new cursor positions
    if (mx != ctx->prevMouseX || my != ctx->prevMouseY) {
        dirtyCursorArea(ctx, ctx->prevMouseX, ctx->prevMouseY);
        dirtyCursorArea(ctx, mx, my);

        // Update cursor shape based on what the mouse is hovering over
        updateCursorShape(ctx);
    }

    // Handle active drag
    if (ctx->stack.dragWindow >= 0) {
        if (buttons & 1) {
            wmDragMove(&ctx->stack, &ctx->dirty, mx, my);
        } else {
            wmDragEnd(&ctx->stack);
        }
        return;
    }

    // Handle active resize
    if (ctx->stack.resizeWindow >= 0) {
        if (buttons & 1) {
            wmResizeMove(&ctx->stack, &ctx->dirty, &ctx->display, mx, my);
        } else {
            wmResizeEnd(&ctx->stack);
        }
        return;
    }

    // Handle active scrollbar thumb drag
    if (ctx->stack.scrollWindow >= 0) {
        if (buttons & 1) {
            wmScrollbarDrag(&ctx->stack, &ctx->dirty, mx, my);
        } else {
            wmScrollbarEnd(&ctx->stack);
        }
        return;
    }

    // Handle system menu interaction
    if (ctx->sysMenu.active) {
        if (mx >= ctx->sysMenu.popupX && mx < ctx->sysMenu.popupX + ctx->sysMenu.popupW &&
            my >= ctx->sysMenu.popupY && my < ctx->sysMenu.popupY + ctx->sysMenu.popupH) {

            // Hover tracking
            int32_t relY    = my - ctx->sysMenu.popupY - 2;
            int32_t itemIdx = relY / ctx->font.charHeight;

            if (itemIdx >= 0 && itemIdx < ctx->sysMenu.itemCount && ctx->sysMenu.items[itemIdx].separator) {
                itemIdx = -1;
            }

            if (itemIdx != ctx->sysMenu.hoverItem) {
                ctx->sysMenu.hoverItem = itemIdx;
                dirtyListAdd(&ctx->dirty, ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH);
            }

            // Click on item
            if ((buttons & 1) && !(prevBtn & 1)) {
                if (itemIdx >= 0 && itemIdx < ctx->sysMenu.itemCount) {
                    SysMenuItemT *item = &ctx->sysMenu.items[itemIdx];

                    if (item->enabled && !item->separator) {
                        executeSysMenuCmd(ctx, item->cmd);
                    }
                }
            }

            return;
        }

        // Click outside system menu — close it, let event fall through
        if ((buttons & 1) && !(prevBtn & 1)) {
            closeSysMenu(ctx);
        }
    }

    // Handle popup menu interaction (with cascading submenu support)
    if (ctx->popup.active) {
        // Check if mouse is inside current (deepest) popup level
        bool inCurrent = (mx >= ctx->popup.popupX && mx < ctx->popup.popupX + ctx->popup.popupW &&
                          my >= ctx->popup.popupY && my < ctx->popup.popupY + ctx->popup.popupH);

        if (inCurrent) {
            // Hover tracking in current level
            int32_t relY    = my - ctx->popup.popupY - 2;
            int32_t itemIdx = relY / ctx->font.charHeight;

            if (itemIdx < 0) {
                itemIdx = 0;
            }

            if (ctx->popup.menu && itemIdx >= ctx->popup.menu->itemCount) {
                itemIdx = ctx->popup.menu->itemCount - 1;
            }

            if (itemIdx != ctx->popup.hoverItem) {
                int32_t prevHover = ctx->popup.hoverItem;
                ctx->popup.hoverItem = itemIdx;
                dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                             ctx->popup.popupW, ctx->popup.popupH);

                // If hovering a submenu item, open the submenu
                if (ctx->popup.menu && itemIdx >= 0 && itemIdx < ctx->popup.menu->itemCount) {
                    MenuItemT *hItem = &ctx->popup.menu->items[itemIdx];

                    if (hItem->subMenu && hItem->enabled) {
                        openSubMenu(ctx);
                    }
                }

                // If we moved away from a submenu item to a non-submenu item,
                // close any child submenus that were opened from this level
                if (prevHover >= 0 && ctx->popup.menu && prevHover < ctx->popup.menu->itemCount) {
                    // Already handled: openSubMenu replaces the child, and if current
                    // item is not a submenu, no child opens. But we may still have
                    // a stale child — check if depth was increased by a previous hover.
                    // This case is handled below by the parent-level hit test popping levels.
                }
            }

            // Click on item in current level
            if ((buttons & 1) && !(prevBtn & 1)) {
                if (ctx->popup.menu && itemIdx >= 0 && itemIdx < ctx->popup.menu->itemCount) {
                    MenuItemT *item = &ctx->popup.menu->items[itemIdx];

                    if (item->subMenu && item->enabled) {
                        // Clicking a submenu item opens it (already open from hover, but ensure)
                        openSubMenu(ctx);
                    } else if (item->enabled && !item->separator) {
                        // Toggle check/radio state before closing
                        if (item->type == MenuItemCheckE || item->type == MenuItemRadioE) {
                            clickMenuCheckRadio(ctx->popup.menu, itemIdx);
                        }

                        // Close popup BEFORE calling onMenu (onMenu may run a nested event loop)
                        int32_t menuId = item->id;
                        WindowT *win   = findWindowById(ctx, ctx->popup.windowId);
                        closeAllPopups(ctx);

                        if (win && win->onMenu) {
                            win->onMenu(win, menuId);
                        }
                    }
                }
            }
        } else {
            // Mouse is not in current popup — check parent levels (deepest first)
            bool inParent = false;

            for (int32_t lvl = ctx->popup.depth - 1; lvl >= 0; lvl--) {
                PopupLevelT *pl = &ctx->popup.parentStack[lvl];

                if (mx >= pl->popupX && mx < pl->popupX + pl->popupW &&
                    my >= pl->popupY && my < pl->popupY + pl->popupH) {

                    // Close all levels deeper than this one
                    while (ctx->popup.depth > lvl + 1) {
                        closePopupLevel(ctx);
                    }

                    // Now close the level that was the "current" when we entered this parent
                    closePopupLevel(ctx);

                    // Now current level IS this parent — update hover
                    int32_t relY    = my - ctx->popup.popupY - 2;
                    int32_t itemIdx = relY / ctx->font.charHeight;

                    if (itemIdx < 0) {
                        itemIdx = 0;
                    }

                    if (ctx->popup.menu && itemIdx >= ctx->popup.menu->itemCount) {
                        itemIdx = ctx->popup.menu->itemCount - 1;
                    }

                    ctx->popup.hoverItem = itemIdx;
                    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                                 ctx->popup.popupW, ctx->popup.popupH);

                    // If the newly hovered item has a submenu, open it
                    if (ctx->popup.menu && itemIdx >= 0 && itemIdx < ctx->popup.menu->itemCount) {
                        MenuItemT *hItem = &ctx->popup.menu->items[itemIdx];

                        if (hItem->subMenu && hItem->enabled) {
                            openSubMenu(ctx);
                        }
                    }

                    inParent = true;
                    break;
                }
            }

            if (!inParent) {
                if (ctx->popup.isContextMenu) {
                    // Context menu: any click outside closes it
                    if ((buttons & 1) && !(prevBtn & 1)) {
                        closeAllPopups(ctx);
                    }
                } else {
                    // Menu bar popup: check if mouse is on the menu bar for switching
                    WindowT *win = findWindowById(ctx, ctx->popup.windowId);

                    if (win && win->menuBar) {
                        int32_t barY = win->y + CHROME_BORDER_WIDTH + CHROME_TITLE_HEIGHT;

                        if (my >= barY && my < barY + CHROME_MENU_HEIGHT &&
                            mx >= win->x + CHROME_TOTAL_SIDE &&
                            mx < win->x + win->w - CHROME_TOTAL_SIDE) {

                            int32_t relX = mx - win->x;

                            for (int32_t i = 0; i < win->menuBar->menuCount; i++) {
                                MenuT *menu = &win->menuBar->menus[i];

                                if (relX >= menu->barX && relX < menu->barX + menu->barW) {
                                    if (i != ctx->popup.menuIdx || ctx->popup.depth > 0) {
                                        openPopupAtMenu(ctx, win, i);
                                    }

                                    break;
                                }
                            }
                        } else if ((buttons & 1) && !(prevBtn & 1)) {
                            closeAllPopups(ctx);
                        }
                    } else if ((buttons & 1) && !(prevBtn & 1)) {
                        closeAllPopups(ctx);
                    }
                }
            }
        }

        return;
    }

    // Handle left button press
    if ((buttons & 1) && !(prevBtn & 1)) {
        handleMouseButton(ctx, mx, my, buttons);
    }

    // Handle right button press — context menus
    if ((buttons & 2) && !(prevBtn & 2)) {
        int32_t hitPart;
        int32_t hitIdx = wmHitTest(&ctx->stack, mx, my, &hitPart);

        if (hitIdx >= 0 && hitPart == 0) {
            WindowT *win = ctx->stack.windows[hitIdx];

            // Raise and focus if not already
            if (hitIdx != ctx->stack.focusedIdx) {
                wmRaiseWindow(&ctx->stack, &ctx->dirty, hitIdx);
                hitIdx = ctx->stack.count - 1;
                wmSetFocus(&ctx->stack, &ctx->dirty, hitIdx);
                win = ctx->stack.windows[hitIdx];
            }

            // Check widget context menu first
            MenuT *ctxMenu = NULL;

            if (win->widgetRoot) {
                int32_t relX = mx - win->x - win->contentX;
                int32_t relY = my - win->y - win->contentY;
                WidgetT *hit = widgetHitTest(win->widgetRoot, relX, relY);

                // Walk up the tree to find a context menu
                while (hit && !hit->contextMenu) {
                    hit = hit->parent;
                }

                if (hit) {
                    ctxMenu = hit->contextMenu;
                }
            }

            // Fall back to window context menu
            if (!ctxMenu) {
                ctxMenu = win->contextMenu;
            }

            if (ctxMenu) {
                openContextMenu(ctx, win, ctxMenu, mx, my);
            }
        }
    }

    // Handle button release on content — send to focused window
    if (!(buttons & 1) && (prevBtn & 1)) {
        if (ctx->stack.focusedIdx >= 0) {
            WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

            if (win->onMouse) {
                int32_t relX = mx - win->x - win->contentX;
                int32_t relY = my - win->y - win->contentY;
                win->onMouse(win, relX, relY, buttons);
            }
        }
    }

    // Mouse movement in content area — send to focused window
    if ((mx != ctx->prevMouseX || my != ctx->prevMouseY) &&
        ctx->stack.focusedIdx >= 0 && (buttons & 1)) {
        WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

        if (win->onMouse) {
            int32_t relX = mx - win->x - win->contentX;
            int32_t relY = my - win->y - win->contentY;
            win->onMouse(win, relX, relY, buttons);
        }
    }
}


// ============================================================
// drawCursorAt
// ============================================================

static void drawCursorAt(AppContextT *ctx, int32_t x, int32_t y) {
    const CursorT *cur = &ctx->cursors[ctx->cursorId];

    drawMaskedBitmap(&ctx->display, &ctx->blitOps, x - cur->hotX, y - cur->hotY, cur->width, cur->height, cur->andMask, cur->xorData, ctx->cursorFg, ctx->cursorBg);
}


// ============================================================
// drawPopupLevel — draw one popup menu (bevel + items)
// ============================================================

static void drawPopupLevel(AppContextT *ctx, DisplayT *d, const BlitOpsT *ops, const MenuT *menu, int32_t px, int32_t py, int32_t pw, int32_t ph, int32_t hoverItem, const RectT *clipTo) {
    RectT popRect = { px, py, pw, ph };
    RectT popIsect;

    if (!rectIntersect(clipTo, &popRect, &popIsect)) {
        return;
    }

    // Detect if menu has check/radio items (for left margin)
    bool hasCheck = false;

    for (int32_t k = 0; k < menu->itemCount; k++) {
        if (menu->items[k].type == MenuItemCheckE || menu->items[k].type == MenuItemRadioE) {
            hasCheck = true;
            break;
        }
    }

    int32_t checkMargin = hasCheck ? MENU_CHECK_WIDTH : 0;

    // Draw popup background
    BevelStyleT popBevel;
    popBevel.highlight = ctx->colors.windowHighlight;
    popBevel.shadow    = ctx->colors.windowShadow;
    popBevel.face      = ctx->colors.menuBg;
    popBevel.width     = 2;
    drawBevel(d, ops, px, py, pw, ph, &popBevel);

    // Draw menu items
    int32_t itemY = py + 2;

    for (int32_t k = 0; k < menu->itemCount; k++) {
        const MenuItemT *item = &menu->items[k];

        if (item->separator) {
            drawHLine(d, ops, px + 2, itemY + ctx->font.charHeight / 2, pw - 4, ctx->colors.windowShadow);
            itemY += ctx->font.charHeight;
            continue;
        }

        uint32_t bg = ctx->colors.menuBg;
        uint32_t fg = ctx->colors.menuFg;

        if (k == hoverItem) {
            bg = ctx->colors.menuHighlightBg;
            fg = ctx->colors.menuHighlightFg;
        }

        rectFill(d, ops, px + 2, itemY, pw - 4, ctx->font.charHeight, bg);
        drawTextAccel(d, ops, &ctx->font, px + CHROME_TITLE_PAD + 2 + checkMargin, itemY, item->label, fg, bg, true);

        // Draw check/radio indicator
        if (item->checked) {
            int32_t cy = itemY + ctx->font.charHeight / 2;
            int32_t cx = px + 2 + MENU_CHECK_WIDTH / 2;

            if (item->type == MenuItemCheckE) {
                // Checkmark: small tick shape
                drawVLine(d, ops, cx - 2, cy - 1, 2, fg);
                drawVLine(d, ops, cx - 1, cy,     2, fg);
                drawVLine(d, ops, cx,     cy + 1,  2, fg);
                drawVLine(d, ops, cx + 1, cy,     2, fg);
                drawVLine(d, ops, cx + 2, cy - 1, 2, fg);
                drawVLine(d, ops, cx + 3, cy - 2, 2, fg);
            } else if (item->type == MenuItemRadioE) {
                // Filled diamond bullet (5x5)
                drawHLine(d, ops, cx,     cy - 2, 1, fg);
                drawHLine(d, ops, cx - 1, cy - 1, 3, fg);
                drawHLine(d, ops, cx - 2, cy,     5, fg);
                drawHLine(d, ops, cx - 1, cy + 1, 3, fg);
                drawHLine(d, ops, cx,     cy + 2, 1, fg);
            }
        }

        // Draw submenu arrow indicator
        if (item->subMenu) {
            int32_t arrowX = px + pw - SUBMENU_ARROW_WIDTH - 2;
            int32_t arrowY = itemY + ctx->font.charHeight / 2;

            for (int32_t row = -3; row <= 3; row++) {
                int32_t len = 4 - (row < 0 ? -row : row);

                if (len > 0) {
                    drawHLine(d, ops, arrowX + (row < 0 ? 3 + row : 3 - row), arrowY + row, len, fg);
                }
            }
        }

        itemY += ctx->font.charHeight;
    }
}


// ============================================================
// dvxCreateWindow
// ============================================================

WindowT *dvxCreateWindow(AppContextT *ctx, const char *title, int32_t x, int32_t y, int32_t w, int32_t h, bool resizable) {
    WindowT *win = wmCreateWindow(&ctx->stack, &ctx->display, title, x, y, w, h, resizable);

    if (win) {
        // Raise and focus
        int32_t idx = ctx->stack.count - 1;
        wmSetFocus(&ctx->stack, &ctx->dirty, idx);
        dirtyListAdd(&ctx->dirty, win->x, win->y, win->w, win->h);
    }

    return win;
}


// ============================================================
// dvxAddAccel
// ============================================================

void dvxAddAccel(AccelTableT *table, int32_t key, int32_t modifiers, int32_t cmdId) {
    if (!table || table->count >= MAX_ACCEL_ENTRIES) {
        return;
    }

    AccelEntryT *e = &table->entries[table->count++];
    e->key       = key;
    e->modifiers = modifiers;
    e->cmdId     = cmdId;
}


// ============================================================
// dvxClipboardCopy
// ============================================================

void dvxClipboardCopy(const char *text, int32_t len) {
    clipboardCopy(text, len);
}


// ============================================================
// dvxClipboardGet
// ============================================================

const char *dvxClipboardGet(int32_t *outLen) {
    return clipboardGet(outLen);
}


// ============================================================
// dvxCreateAccelTable
// ============================================================

AccelTableT *dvxCreateAccelTable(void) {
    AccelTableT *table = (AccelTableT *)calloc(1, sizeof(AccelTableT));
    return table;
}


// ============================================================
// dvxDestroyWindow
// ============================================================

void dvxDestroyWindow(AppContextT *ctx, WindowT *win) {
    dirtyListAdd(&ctx->dirty, win->x, win->y, win->w, win->h);
    wmDestroyWindow(&ctx->stack, win);

    // Focus the new top window
    if (ctx->stack.count > 0) {
        wmSetFocus(&ctx->stack, &ctx->dirty, ctx->stack.count - 1);
    }
}


// ============================================================
// dvxFitWindow
// ============================================================

void dvxFitWindow(AppContextT *ctx, WindowT *win) {
    if (!ctx || !win || !win->widgetRoot) {
        return;
    }

    // Measure the widget tree to get minimum content size
    widgetCalcMinSizeTree(win->widgetRoot, &ctx->font);

    int32_t contentW = win->widgetRoot->calcMinW;
    int32_t contentH = win->widgetRoot->calcMinH;

    // Compute chrome overhead
    int32_t topChrome = CHROME_TOTAL_TOP;
    if (win->menuBar) {
        topChrome += CHROME_MENU_HEIGHT;
    }

    int32_t newW = contentW + CHROME_TOTAL_SIDE * 2;
    int32_t newH = contentH + topChrome + CHROME_TOTAL_BOTTOM;

    // Dirty old position
    dirtyListAdd(&ctx->dirty, win->x, win->y, win->w, win->h);

    // Resize
    win->w = newW;
    win->h = newH;
    wmUpdateContentRect(win);
    wmReallocContentBuf(win, &ctx->display);

    // Dirty new position
    dirtyListAdd(&ctx->dirty, win->x, win->y, win->w, win->h);
}


// ============================================================
// dvxFreeAccelTable
// ============================================================

void dvxFreeAccelTable(AccelTableT *table) {
    free(table);
}


// ============================================================
// dvxGetBlitOps
// ============================================================

const BlitOpsT *dvxGetBlitOps(const AppContextT *ctx) {
    return &ctx->blitOps;
}


// ============================================================
// dvxGetColors
// ============================================================

const ColorSchemeT *dvxGetColors(const AppContextT *ctx) {
    return &ctx->colors;
}


// ============================================================
// dvxGetDisplay
// ============================================================

DisplayT *dvxGetDisplay(AppContextT *ctx) {
    return &ctx->display;
}


// ============================================================
// dvxGetFont
// ============================================================

const BitmapFontT *dvxGetFont(const AppContextT *ctx) {
    return &ctx->font;
}


// ============================================================
// dvxInit
// ============================================================

int32_t dvxInit(AppContextT *ctx, int32_t requestedW, int32_t requestedH, int32_t preferredBpp) {
    memset(ctx, 0, sizeof(*ctx));

    // Disable Ctrl+C/Break termination
    signal(SIGINT, SIG_IGN);

    // Initialize video
    if (videoInit(&ctx->display, requestedW, requestedH, preferredBpp) != 0) {
        return -1;
    }

    // Initialize blit ops
    drawInit(&ctx->blitOps, &ctx->display);

    // Initialize window stack
    wmInit(&ctx->stack);

    // Initialize dirty list
    dirtyListInit(&ctx->dirty);

    // Set up font (use 8x16)
    ctx->font = dvxFont8x16;

    // Set up cursors
    memcpy(ctx->cursors, dvxCursors, sizeof(dvxCursors));
    ctx->cursorId = CURSOR_ARROW;

    // Initialize colors
    initColorScheme(ctx);

    // Cache cursor colors
    ctx->cursorFg = packColor(&ctx->display, 255, 255, 255);
    ctx->cursorBg = packColor(&ctx->display, 0, 0, 0);

    // Initialize mouse
    initMouse(ctx);

    ctx->running          = true;
    ctx->lastIconClickId   = -1;
    ctx->lastIconClickTime = 0;
    ctx->lastCloseClickId  = -1;
    ctx->lastCloseClickTime = 0;

    // Dirty the entire screen for first paint
    dirtyListAdd(&ctx->dirty, 0, 0, ctx->display.width, ctx->display.height);

    return 0;
}


// ============================================================
// dvxInvalidateRect
// ============================================================

void dvxInvalidateRect(AppContextT *ctx, WindowT *win, int32_t x, int32_t y, int32_t w, int32_t h) {
    // Convert from content-relative to screen coordinates
    int32_t screenX = win->x + win->contentX + x;
    int32_t screenY = win->y + win->contentY + y;

    dirtyListAdd(&ctx->dirty, screenX, screenY, w, h);
}


// ============================================================
// dvxInvalidateWindow
// ============================================================

void dvxInvalidateWindow(AppContextT *ctx, WindowT *win) {
    dirtyListAdd(&ctx->dirty, win->x, win->y, win->w, win->h);
}


// ============================================================
// dvxMaximizeWindow
// ============================================================

void dvxMaximizeWindow(AppContextT *ctx, WindowT *win) {
    wmMaximize(&ctx->stack, &ctx->dirty, &ctx->display, win);
}


// ============================================================
// dvxMinimizeWindow
// ============================================================

void dvxMinimizeWindow(AppContextT *ctx, WindowT *win) {
    wmMinimize(&ctx->stack, &ctx->dirty, win);
}


// ============================================================
// dvxQuit
// ============================================================

void dvxQuit(AppContextT *ctx) {
    ctx->running = false;
}


// ============================================================
// dvxRun
// ============================================================

void dvxRun(AppContextT *ctx) {
    while (dvxUpdate(ctx)) {
        // dvxUpdate returns false when the GUI wants to exit
    }
}


// ============================================================
// dvxUpdate
// ============================================================

bool dvxUpdate(AppContextT *ctx) {
    if (!ctx->running) {
        return false;
    }

    pollMouse(ctx);
    pollKeyboard(ctx);
    dispatchEvents(ctx);
    updateTooltip(ctx);
    pollAnsiTermWidgets(ctx);

    // Periodically refresh one minimized window thumbnail (staggered)
    ctx->frameCount++;

    if (ctx->frameCount % ICON_REFRESH_INTERVAL == 0) {
        refreshMinimizedIcons(ctx);
    }

    if (ctx->dirty.count > 0) {
        compositeAndFlush(ctx);
    } else if (ctx->idleCallback) {
        ctx->idleCallback(ctx->idleCtx);
    } else {
        __dpmi_yield();
    }

    // After compositing, release key-pressed button (one frame of animation)
    if (sKeyPressedBtn) {
        if (sKeyPressedBtn->type == WidgetImageButtonE) {
            sKeyPressedBtn->as.imageButton.pressed = false;
        } else {
            sKeyPressedBtn->as.button.pressed = false;
        }

        if (sKeyPressedBtn->onClick) {
            sKeyPressedBtn->onClick(sKeyPressedBtn);
        }

        wgtInvalidate(sKeyPressedBtn);
        sKeyPressedBtn = NULL;
    }

    ctx->prevMouseX       = ctx->mouseX;
    ctx->prevMouseY       = ctx->mouseY;
    ctx->prevMouseButtons = ctx->mouseButtons;

    return ctx->running;
}


// ============================================================
// dvxShutdown
// ============================================================

void dvxShutdown(AppContextT *ctx) {
    // Destroy all remaining windows
    while (ctx->stack.count > 0) {
        wmDestroyWindow(&ctx->stack, ctx->stack.windows[ctx->stack.count - 1]);
    }

    videoShutdown(&ctx->display);
}


// ============================================================
// dvxSetTitle
// ============================================================

void dvxSetTitle(AppContextT *ctx, WindowT *win, const char *title) {
    wmSetTitle(win, &ctx->dirty, title);
}


// ============================================================
// dvxSetWindowIcon
// ============================================================

int32_t dvxSetWindowIcon(AppContextT *ctx, WindowT *win, const char *path) {
    return wmSetIcon(win, path, &ctx->display);
}


// ============================================================
// executeSysMenuCmd
// ============================================================

static void executeSysMenuCmd(AppContextT *ctx, int32_t cmd) {
    WindowT *win = findWindowById(ctx, ctx->sysMenu.windowId);

    closeSysMenu(ctx);

    if (!win) {
        return;
    }

    switch (cmd) {
        case SysMenuRestoreE:
            if (win->maximized) {
                wmRestore(&ctx->stack, &ctx->dirty, &ctx->display, win);
            }
            break;

        case SysMenuMoveE:
            ctx->kbMoveResize.mode     = KbModeMoveE;
            ctx->kbMoveResize.windowId = win->id;
            ctx->kbMoveResize.origX    = win->x;
            ctx->kbMoveResize.origY    = win->y;
            break;

        case SysMenuSizeE:
            ctx->kbMoveResize.mode     = KbModeResizeE;
            ctx->kbMoveResize.windowId = win->id;
            ctx->kbMoveResize.origX    = win->x;
            ctx->kbMoveResize.origY    = win->y;
            ctx->kbMoveResize.origW    = win->w;
            ctx->kbMoveResize.origH    = win->h;
            break;

        case SysMenuMinimizeE:
            if (ctx->modalWindow != win) {
                wmMinimize(&ctx->stack, &ctx->dirty, win);
                dirtyListAdd(&ctx->dirty, 0, ctx->display.height - ICON_TOTAL_SIZE - ICON_SPACING, ctx->display.width, ICON_TOTAL_SIZE + ICON_SPACING);
            }
            break;

        case SysMenuMaximizeE:
            if (win->resizable && !win->maximized) {
                wmMaximize(&ctx->stack, &ctx->dirty, &ctx->display, win);
            }
            break;

        case SysMenuCloseE:
            if (win->onClose) {
                win->onClose(win);
            } else {
                dvxDestroyWindow(ctx, win);
            }
            break;
    }
}


// ============================================================
// findWindowById
// ============================================================

static WindowT *findWindowById(AppContextT *ctx, int32_t id) {
    for (int32_t i = 0; i < ctx->stack.count; i++) {
        if (ctx->stack.windows[i]->id == id) {
            return ctx->stack.windows[i];
        }
    }

    return NULL;
}


// ============================================================
// handleMouseButton
// ============================================================

static void handleMouseButton(AppContextT *ctx, int32_t mx, int32_t my, int32_t buttons) {
    // Modal window gating: only the modal window receives clicks
    if (ctx->modalWindow) {
        int32_t hitPart;
        int32_t hitIdx = wmHitTest(&ctx->stack, mx, my, &hitPart);

        if (hitIdx >= 0 && ctx->stack.windows[hitIdx] != ctx->modalWindow) {
            return;
        }
    }

    // Check for click on minimized icon first
    int32_t iconIdx = wmMinimizedIconHit(&ctx->stack, &ctx->display, mx, my);

    if (iconIdx >= 0) {
        WindowT *iconWin = ctx->stack.windows[iconIdx];
        clock_t  now     = clock();

        if (ctx->lastIconClickId == iconWin->id &&
            (now - ctx->lastIconClickTime) < DBLCLICK_THRESHOLD) {
            // Double-click: restore minimized window
            // Dirty the entire icon strip area
            dirtyListAdd(&ctx->dirty, 0,
                         ctx->display.height - ICON_TOTAL_SIZE - ICON_SPACING,
                         ctx->display.width, ICON_TOTAL_SIZE + ICON_SPACING);
            wmRestoreMinimized(&ctx->stack, &ctx->dirty, iconWin);
            ctx->lastIconClickId = -1;
        } else {
            // First click — record for double-click detection
            ctx->lastIconClickTime = now;
            ctx->lastIconClickId   = iconWin->id;
        }

        return;
    }

    int32_t hitPart;
    int32_t hitIdx = wmHitTest(&ctx->stack, mx, my, &hitPart);

    if (hitIdx < 0) {
        return; // clicked on desktop
    }

    WindowT *win = ctx->stack.windows[hitIdx];

    // Raise and focus if not already
    if (hitIdx != ctx->stack.focusedIdx) {
        wmRaiseWindow(&ctx->stack, &ctx->dirty, hitIdx);
        // After raise, the window is now at count-1
        hitIdx = ctx->stack.count - 1;
        wmSetFocus(&ctx->stack, &ctx->dirty, hitIdx);
    }

    switch (hitPart) {
        case 0: // content
            if (win->onMouse) {
                int32_t relX = mx - win->x - win->contentX;
                int32_t relY = my - win->y - win->contentY;
                win->onMouse(win, relX, relY, buttons);
            }
            break;

        case 1: // title bar — start drag
            wmDragBegin(&ctx->stack, hitIdx, mx, my);
            break;

        case 2: // close button (double-click to close, single-click opens system menu)
            {
                clock_t now = clock();

                if (ctx->lastCloseClickId == win->id &&
                    (now - ctx->lastCloseClickTime) < DBLCLICK_THRESHOLD) {
                    ctx->lastCloseClickId = -1;
                    closeSysMenu(ctx);

                    if (win->onClose) {
                        win->onClose(win);
                    } else {
                        dvxDestroyWindow(ctx, win);
                    }
                } else {
                    ctx->lastCloseClickTime = now;
                    ctx->lastCloseClickId   = win->id;
                    openSysMenu(ctx, win);
                }
            }
            break;

        case 3: // resize edge
            {
                int32_t edge = wmResizeEdgeHit(win, mx, my);
                wmResizeBegin(&ctx->stack, hitIdx, edge, mx, my);
            }
            break;

        case 4: // menu bar
            {
                if (!win->menuBar) {
                    break;
                }

                int32_t relX = mx - win->x;

                for (int32_t i = 0; i < win->menuBar->menuCount; i++) {
                    MenuT *menu = &win->menuBar->menus[i];

                    if (relX >= menu->barX && relX < menu->barX + menu->barW) {
                        openPopupAtMenu(ctx, win, i);
                        break;
                    }
                }
            }
            break;

        case 5: // vertical scrollbar
            wmScrollbarClick(&ctx->stack, &ctx->dirty, hitIdx, 0, mx, my);
            break;

        case 6: // horizontal scrollbar
            wmScrollbarClick(&ctx->stack, &ctx->dirty, hitIdx, 1, mx, my);
            break;

        case 7: // minimize (not allowed for modal windows)
            if (ctx->modalWindow != win) {
                wmMinimize(&ctx->stack, &ctx->dirty, win);
                // Dirty the icon strip area so the new icon gets drawn
                dirtyListAdd(&ctx->dirty, 0,
                             ctx->display.height - ICON_TOTAL_SIZE - ICON_SPACING,
                             ctx->display.width, ICON_TOTAL_SIZE + ICON_SPACING);
            }
            break;

        case 8: // maximize / restore
            if (win->maximized) {
                wmRestore(&ctx->stack, &ctx->dirty, &ctx->display, win);
            } else {
                wmMaximize(&ctx->stack, &ctx->dirty, &ctx->display, win);
            }
            break;
    }
}


// ============================================================
// initColorScheme
// ============================================================

static void initColorScheme(AppContextT *ctx) {
    DisplayT *d = &ctx->display;

    // GEOS Ensemble Motif-style color scheme
    ctx->colors.desktop          = packColor(d, 0, 128, 128);    // GEOS teal desktop
    ctx->colors.windowFace       = packColor(d, 192, 192, 192);  // standard Motif grey
    ctx->colors.windowHighlight  = packColor(d, 255, 255, 255);
    ctx->colors.windowShadow     = packColor(d, 128, 128, 128);
    ctx->colors.activeTitleBg    = packColor(d, 48, 48, 48);      // GEOS dark charcoal
    ctx->colors.activeTitleFg    = packColor(d, 255, 255, 255);
    ctx->colors.inactiveTitleBg  = packColor(d, 160, 160, 160);  // lighter grey
    ctx->colors.inactiveTitleFg  = packColor(d, 64, 64, 64);
    ctx->colors.contentBg        = packColor(d, 192, 192, 192);
    ctx->colors.contentFg        = packColor(d, 0, 0, 0);
    ctx->colors.menuBg           = packColor(d, 192, 192, 192);
    ctx->colors.menuFg           = packColor(d, 0, 0, 0);
    ctx->colors.menuHighlightBg  = packColor(d, 48, 48, 48);
    ctx->colors.menuHighlightFg  = packColor(d, 255, 255, 255);
    ctx->colors.buttonFace       = packColor(d, 192, 192, 192);
    ctx->colors.scrollbarBg      = packColor(d, 192, 192, 192);
    ctx->colors.scrollbarFg      = packColor(d, 128, 128, 128);
    ctx->colors.scrollbarTrough  = packColor(d, 160, 160, 160);  // GEOS lighter trough
}


// ============================================================
// initMouse
// ============================================================

static void initMouse(AppContextT *ctx) {
    __dpmi_regs r;

    // Reset mouse driver
    memset(&r, 0, sizeof(r));
    r.x.ax = 0x0000;
    __dpmi_int(0x33, &r);

    // Set horizontal range to match screen width
    memset(&r, 0, sizeof(r));
    r.x.ax = 0x0007;
    r.x.cx = 0;
    r.x.dx = ctx->display.width - 1;
    __dpmi_int(0x33, &r);

    // Set vertical range to match screen height
    memset(&r, 0, sizeof(r));
    r.x.ax = 0x0008;
    r.x.cx = 0;
    r.x.dx = ctx->display.height - 1;
    __dpmi_int(0x33, &r);

    // Position cursor at center of screen
    ctx->mouseX     = ctx->display.width / 2;
    ctx->mouseY     = ctx->display.height / 2;
    ctx->prevMouseX = ctx->mouseX;
    ctx->prevMouseY = ctx->mouseY;

    // Set mouse position
    memset(&r, 0, sizeof(r));
    r.x.ax = 0x0004;
    r.x.cx = ctx->mouseX;
    r.x.dx = ctx->mouseY;
    __dpmi_int(0x33, &r);
}


// ============================================================
// openContextMenu — open a context menu at a screen position
// ============================================================

static void openContextMenu(AppContextT *ctx, WindowT *win, MenuT *menu, int32_t screenX, int32_t screenY) {
    if (!menu || menu->itemCount <= 0) {
        return;
    }

    closeAllPopups(ctx);
    closeSysMenu(ctx);

    ctx->popup.active        = true;
    ctx->popup.isContextMenu = true;
    ctx->popup.windowId      = win->id;
    ctx->popup.menuIdx       = -1;
    ctx->popup.menu          = menu;
    ctx->popup.hoverItem     = -1;
    ctx->popup.depth         = 0;

    calcPopupSize(ctx, menu, &ctx->popup.popupW, &ctx->popup.popupH);

    // Position at mouse, clamped to screen
    ctx->popup.popupX = screenX;
    ctx->popup.popupY = screenY;

    if (ctx->popup.popupX + ctx->popup.popupW > ctx->display.width) {
        ctx->popup.popupX = ctx->display.width - ctx->popup.popupW;
    }

    if (ctx->popup.popupY + ctx->popup.popupH > ctx->display.height) {
        ctx->popup.popupY = ctx->display.height - ctx->popup.popupH;
    }

    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                 ctx->popup.popupW, ctx->popup.popupH);
}


// ============================================================
// openPopupAtMenu — open top-level popup for a menu bar menu
// ============================================================

static void openPopupAtMenu(AppContextT *ctx, WindowT *win, int32_t menuIdx) {
    if (!win->menuBar || menuIdx < 0 || menuIdx >= win->menuBar->menuCount) {
        return;
    }

    // Close any existing popup chain first
    closeAllPopups(ctx);

    MenuT *menu = &win->menuBar->menus[menuIdx];

    ctx->popup.active        = true;
    ctx->popup.isContextMenu = false;
    ctx->popup.windowId      = win->id;
    ctx->popup.menuIdx       = menuIdx;
    ctx->popup.menu          = menu;
    ctx->popup.popupX        = win->x + menu->barX;
    ctx->popup.popupY        = win->y + CHROME_BORDER_WIDTH + CHROME_TITLE_HEIGHT + CHROME_MENU_HEIGHT;
    ctx->popup.hoverItem     = -1;
    ctx->popup.depth         = 0;

    calcPopupSize(ctx, menu, &ctx->popup.popupW, &ctx->popup.popupH);

    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                 ctx->popup.popupW, ctx->popup.popupH);
}


// ============================================================
// openSubMenu — open submenu for the currently hovered item
// ============================================================

static void openSubMenu(AppContextT *ctx) {
    if (!ctx->popup.active || !ctx->popup.menu) {
        return;
    }

    int32_t idx = ctx->popup.hoverItem;

    if (idx < 0 || idx >= ctx->popup.menu->itemCount) {
        return;
    }

    MenuItemT *item = &ctx->popup.menu->items[idx];

    if (!item->subMenu) {
        return;
    }

    if (ctx->popup.depth >= MAX_SUBMENU_DEPTH) {
        return;
    }

    // Push current state to parent stack
    PopupLevelT *pl = &ctx->popup.parentStack[ctx->popup.depth];
    pl->menu      = ctx->popup.menu;
    pl->menuIdx   = ctx->popup.menuIdx;
    pl->popupX    = ctx->popup.popupX;
    pl->popupY    = ctx->popup.popupY;
    pl->popupW    = ctx->popup.popupW;
    pl->popupH    = ctx->popup.popupH;
    pl->hoverItem = ctx->popup.hoverItem;
    ctx->popup.depth++;

    // Open submenu at right edge of current popup, aligned with hovered item
    ctx->popup.menu      = item->subMenu;
    ctx->popup.popupX    = pl->popupX + pl->popupW - 2;
    ctx->popup.popupY    = pl->popupY + 2 + idx * ctx->font.charHeight;
    ctx->popup.hoverItem = -1;

    calcPopupSize(ctx, ctx->popup.menu, &ctx->popup.popupW, &ctx->popup.popupH);

    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY,
                 ctx->popup.popupW, ctx->popup.popupH);
}


// ============================================================
// openSysMenu
// ============================================================

static void openSysMenu(AppContextT *ctx, WindowT *win) {
    // Close any existing popup menus first
    closeAllPopups(ctx);

    if (ctx->sysMenu.active) {
        closeSysMenu(ctx);
        return;
    }

    ctx->sysMenu.itemCount = 0;
    ctx->sysMenu.windowId  = win->id;

    // Restore — enabled only when maximized
    SysMenuItemT *item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "&Restore", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuRestoreE;
    item->separator = false;
    item->enabled   = win->maximized;
    item->accelKey  = accelParse(item->label);

    // Move — disabled when maximized
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "&Move", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuMoveE;
    item->separator = false;
    item->enabled   = !win->maximized;
    item->accelKey  = accelParse(item->label);

    // Size — only if resizable and not maximized
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "&Size", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuSizeE;
    item->separator = false;
    item->enabled   = win->resizable && !win->maximized;
    item->accelKey  = accelParse(item->label);

    // Minimize — not available on modal windows
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "Mi&nimize", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuMinimizeE;
    item->separator = false;
    item->enabled   = !win->modal;
    item->accelKey  = accelParse(item->label);

    // Maximize — only if resizable and not maximized
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "Ma&ximize", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuMaximizeE;
    item->separator = false;
    item->enabled   = win->resizable && !win->maximized;
    item->accelKey  = accelParse(item->label);

    // Separator
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    memset(item, 0, sizeof(*item));
    item->separator = true;

    // Close
    item = &ctx->sysMenu.items[ctx->sysMenu.itemCount++];
    strncpy(item->label, "&Close", MAX_MENU_LABEL - 1);
    item->cmd       = SysMenuCloseE;
    item->separator = false;
    item->enabled   = true;
    item->accelKey  = accelParse(item->label);

    // Compute popup geometry — position below the close gadget
    ctx->sysMenu.popupX = win->x + CHROME_BORDER_WIDTH;
    ctx->sysMenu.popupY = win->y + CHROME_BORDER_WIDTH + CHROME_TITLE_HEIGHT;

    if (win->menuBar) {
        ctx->sysMenu.popupY += CHROME_MENU_HEIGHT;
    }

    int32_t maxW = 0;

    for (int32_t i = 0; i < ctx->sysMenu.itemCount; i++) {
        if (!ctx->sysMenu.items[i].separator) {
            int32_t w = textWidthAccel(&ctx->font, ctx->sysMenu.items[i].label);

            if (w > maxW) {
                maxW = w;
            }
        }
    }

    ctx->sysMenu.popupW    = maxW + CHROME_TITLE_PAD * 2 + 8;
    ctx->sysMenu.popupH    = ctx->sysMenu.itemCount * ctx->font.charHeight + 4;
    ctx->sysMenu.hoverItem = -1;
    ctx->sysMenu.active    = true;

    dirtyListAdd(&ctx->dirty, ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH);
}


// ============================================================
// pollAnsiTermWidgets — poll and repaint all ANSI term widgets
// ============================================================

static void pollAnsiTermWidgets(AppContextT *ctx) {
    for (int32_t i = 0; i < ctx->stack.count; i++) {
        WindowT *win = ctx->stack.windows[i];

        if (win->widgetRoot) {
            pollAnsiTermWidgetsWalk(ctx, win->widgetRoot, win);
        }
    }
}


// ============================================================
// pollAnsiTermWidgetsWalk — recursive helper
// ============================================================

static void pollAnsiTermWidgetsWalk(AppContextT *ctx, WidgetT *w, WindowT *win) {
    if (w->type == WidgetAnsiTermE) {
        wgtAnsiTermPoll(w);

        int32_t dirtyY = 0;
        int32_t dirtyH = 0;

        if (wgtAnsiTermRepaint(w, &dirtyY, &dirtyH) > 0) {
            win->contentDirty = true;

            // Dirty only the affected rows (in screen coords) instead of
            // the entire window. This dramatically reduces compositor and
            // LFB flush work for cursor blink and single-row updates.
            int32_t scrollY = win->vScroll ? win->vScroll->value : 0;
            int32_t rectX   = win->x + win->contentX;
            int32_t rectY   = win->y + win->contentY + dirtyY - scrollY;
            int32_t rectW   = win->contentW;
            dirtyListAdd(&ctx->dirty, rectX, rectY, rectW, dirtyH);
        }
    }

    for (WidgetT *child = w->firstChild; child; child = child->nextSibling) {
        pollAnsiTermWidgetsWalk(ctx, child, win);
    }
}


// ============================================================
// pollKeyboard
// ============================================================

static void pollKeyboard(AppContextT *ctx) {
    __dpmi_regs r;

    // Read shift state once per poll (INT 16h, AH=12h)
    memset(&r, 0, sizeof(r));
    r.x.ax = 0x1200;
    __dpmi_int(0x16, &r);
    int32_t shiftFlags = r.x.ax & 0xFF;
    ctx->keyModifiers  = shiftFlags;
    bool    shiftHeld  = (shiftFlags & 0x03) != 0; // left or right shift

    // Process buffered keys
    while (1) {
        // Check if key is available (INT 16h, enhanced function 11h)
        r.x.ax = 0x1100;
        __dpmi_int(0x16, &r);

        // Zero flag set = no key available
        if (r.x.flags & 0x40) {
            break;
        }

        // Read the key (INT 16h, enhanced function 10h)
        r.x.ax = 0x1000;
        __dpmi_int(0x16, &r);

        int32_t scancode = (r.x.ax >> 8) & 0xFF;
        int32_t ascii    = r.x.ax & 0xFF;

        // Enhanced INT 16h returns ascii=0xE0 for grey/extended keys
        // (arrows, Home, End, Insert, Delete, etc. on 101-key keyboards).
        // Normalize to 0 so all extended key checks work uniformly.
        if (ascii == 0xE0) {
            ascii = 0;
        }

        // Alt+Tab / Shift+Alt+Tab — cycle windows
        // Alt+Tab: scancode=0xA5, ascii=0x00
        if (ascii == 0 && scancode == 0xA5) {
            if (ctx->stack.count > 1) {
                if (shiftHeld) {
                    // Shift+Alt+Tab — focus the bottom window, raise it
                    wmRaiseWindow(&ctx->stack, &ctx->dirty, 0);
                    wmSetFocus(&ctx->stack, &ctx->dirty, ctx->stack.count - 1);
                } else {
                    // Alt+Tab — send top window to bottom, focus new top
                    WindowT *top = ctx->stack.windows[ctx->stack.count - 1];
                    dirtyListAdd(&ctx->dirty, top->x, top->y, top->w, top->h);

                    // Shift all windows up
                    for (int32_t i = ctx->stack.count - 1; i > 0; i--) {
                        ctx->stack.windows[i] = ctx->stack.windows[i - 1];
                    }

                    ctx->stack.windows[0] = top;
                    top->focused = false;

                    // Focus the new top window
                    wmSetFocus(&ctx->stack, &ctx->dirty, ctx->stack.count - 1);
                    dirtyListAdd(&ctx->dirty, ctx->stack.windows[ctx->stack.count - 1]->x,
                                 ctx->stack.windows[ctx->stack.count - 1]->y,
                                 ctx->stack.windows[ctx->stack.count - 1]->w,
                                 ctx->stack.windows[ctx->stack.count - 1]->h);
                }
            }

            continue;
        }

        // Alt+F4 — close focused window
        if (ascii == 0 && scancode == 0x6B) {
            if (ctx->stack.focusedIdx >= 0) {
                WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

                if (win->onClose) {
                    win->onClose(win);
                }
            }

            continue;
        }

        // F10 — activate menu bar
        if (ascii == 0 && scancode == 0x44) {
            if (ctx->stack.focusedIdx >= 0) {
                WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

                if (win->menuBar && win->menuBar->menuCount > 0) {
                    if (ctx->popup.active) {
                        closeAllPopups(ctx);
                    } else {
                        dispatchAccelKey(ctx, win->menuBar->menus[0].accelKey);
                    }
                }
            }

            continue;
        }

        // Keyboard move/resize mode — intercept all keys
        if (ctx->kbMoveResize.mode != KbModeNoneE) {
            WindowT *kbWin = findWindowById(ctx, ctx->kbMoveResize.windowId);

            if (!kbWin) {
                ctx->kbMoveResize.mode = KbModeNoneE;
                continue;
            }

            if (ascii == 0x1B) {
                // Cancel — restore original position/size
                dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                kbWin->x = ctx->kbMoveResize.origX;
                kbWin->y = ctx->kbMoveResize.origY;

                if (ctx->kbMoveResize.mode == KbModeResizeE) {
                    kbWin->w = ctx->kbMoveResize.origW;
                    kbWin->h = ctx->kbMoveResize.origH;
                    wmUpdateContentRect(kbWin);
                    wmReallocContentBuf(kbWin, &ctx->display);

                    if (kbWin->onResize) {
                        kbWin->onResize(kbWin, kbWin->contentW, kbWin->contentH);
                    }

                    if (kbWin->onPaint) {
                        kbWin->onPaint(kbWin, NULL);
                    }
                }

                dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                ctx->kbMoveResize.mode = KbModeNoneE;
                continue;
            }

            if (ascii == 0x0D) {
                // Confirm
                ctx->kbMoveResize.mode = KbModeNoneE;
                continue;
            }

            if (ctx->kbMoveResize.mode == KbModeMoveE) {
                if (ascii == 0 && scancode == 0x48) {
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                    kbWin->y -= KB_MOVE_STEP;
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                } else if (ascii == 0 && scancode == 0x50) {
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                    kbWin->y += KB_MOVE_STEP;
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                } else if (ascii == 0 && scancode == 0x4B) {
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                    kbWin->x -= KB_MOVE_STEP;
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                } else if (ascii == 0 && scancode == 0x4D) {
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                    kbWin->x += KB_MOVE_STEP;
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                }
            } else {
                // KbModeResizeE
                int32_t newW = kbWin->w;
                int32_t newH = kbWin->h;

                if (ascii == 0 && scancode == 0x4D) {
                    newW += KB_MOVE_STEP;
                } else if (ascii == 0 && scancode == 0x4B) {
                    newW -= KB_MOVE_STEP;
                } else if (ascii == 0 && scancode == 0x50) {
                    newH += KB_MOVE_STEP;
                } else if (ascii == 0 && scancode == 0x48) {
                    newH -= KB_MOVE_STEP;
                }

                if (newW < MIN_WINDOW_W) {
                    newW = MIN_WINDOW_W;
                }

                if (newH < MIN_WINDOW_H) {
                    newH = MIN_WINDOW_H;
                }

                if (kbWin->maxW > 0 && newW > kbWin->maxW) {
                    newW = kbWin->maxW;
                }

                if (kbWin->maxH > 0 && newH > kbWin->maxH) {
                    newH = kbWin->maxH;
                }

                if (newW != kbWin->w || newH != kbWin->h) {
                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                    kbWin->w = newW;
                    kbWin->h = newH;
                    wmUpdateContentRect(kbWin);
                    wmReallocContentBuf(kbWin, &ctx->display);

                    if (kbWin->onResize) {
                        kbWin->onResize(kbWin, kbWin->contentW, kbWin->contentH);
                    }

                    if (kbWin->onPaint) {
                        kbWin->onPaint(kbWin, NULL);
                    }

                    dirtyListAdd(&ctx->dirty, kbWin->x, kbWin->y, kbWin->w, kbWin->h);
                }
            }

            continue;
        }

        // Alt+Space — open/close system menu
        // Enhanced INT 16h: Alt+Space returns scancode 0x02, ascii 0x20
        if (scancode == 0x02 && ascii == 0x20) {
            if (ctx->sysMenu.active) {
                closeSysMenu(ctx);
            } else if (ctx->stack.focusedIdx >= 0) {
                WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];
                openSysMenu(ctx, win);
            }
            continue;
        }

        // System menu keyboard navigation
        if (ctx->sysMenu.active) {
            // Alt+key — close system menu and let it fall through to accel dispatch
            if (ascii == 0 && scancode < 256 && sAltScanToAscii[scancode]) {
                closeSysMenu(ctx);
                // Fall through to dispatchAccelKey below
            } else if (ascii == 0x1B) {
                closeSysMenu(ctx);
                continue;
            } else if (ascii == 0 && scancode == 0x48) {
                // Up arrow
                int32_t idx = ctx->sysMenu.hoverItem;

                for (int32_t tries = 0; tries < ctx->sysMenu.itemCount; tries++) {
                    idx--;

                    if (idx < 0) {
                        idx = ctx->sysMenu.itemCount - 1;
                    }

                    if (!ctx->sysMenu.items[idx].separator) {
                        break;
                    }
                }

                ctx->sysMenu.hoverItem = idx;
                dirtyListAdd(&ctx->dirty, ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH);
                continue;
            } else if (ascii == 0 && scancode == 0x50) {
                // Down arrow
                int32_t idx = ctx->sysMenu.hoverItem;

                for (int32_t tries = 0; tries < ctx->sysMenu.itemCount; tries++) {
                    idx++;

                    if (idx >= ctx->sysMenu.itemCount) {
                        idx = 0;
                    }

                    if (!ctx->sysMenu.items[idx].separator) {
                        break;
                    }
                }

                ctx->sysMenu.hoverItem = idx;
                dirtyListAdd(&ctx->dirty, ctx->sysMenu.popupX, ctx->sysMenu.popupY, ctx->sysMenu.popupW, ctx->sysMenu.popupH);
                continue;
            } else if (ascii == 0x0D) {
                // Enter — execute selected item
                if (ctx->sysMenu.hoverItem >= 0 && ctx->sysMenu.hoverItem < ctx->sysMenu.itemCount) {
                    SysMenuItemT *item = &ctx->sysMenu.items[ctx->sysMenu.hoverItem];

                    if (item->enabled && !item->separator) {
                        executeSysMenuCmd(ctx, item->cmd);
                    }
                } else {
                    closeSysMenu(ctx);
                }
                continue;
            } else if (ascii != 0) {
                // Accelerator key match
                char lc = (char)tolower(ascii);

                for (int32_t k = 0; k < ctx->sysMenu.itemCount; k++) {
                    if (ctx->sysMenu.items[k].accelKey == lc && ctx->sysMenu.items[k].enabled && !ctx->sysMenu.items[k].separator) {
                        executeSysMenuCmd(ctx, ctx->sysMenu.items[k].cmd);
                        goto nextKey;
                    }
                }

                // No sys menu match — try menu bar accelerators
                closeSysMenu(ctx);
                if (ctx->stack.focusedIdx >= 0) {
                    WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

                    if (win->menuBar) {
                        for (int32_t i = 0; i < win->menuBar->menuCount; i++) {
                            if (win->menuBar->menus[i].accelKey == lc) {
                                dispatchAccelKey(ctx, lc);
                                goto nextKey;
                            }
                        }
                    }
                }
                continue;
            } else {
                continue;
            }
        }

        // Check for Alt+key (BIOS returns ascii=0 with specific scancodes)
        if (ascii == 0 && scancode < 256 && sAltScanToAscii[scancode]) {
            char accelKey = sAltScanToAscii[scancode];

            if (dispatchAccelKey(ctx, accelKey)) {
                continue;
            }
        }

        // Popup menu keyboard navigation (arrows, enter, esc)
        if (ctx->popup.active && ascii == 0) {
            MenuT *curMenu = ctx->popup.menu;

            // Up arrow
            if (scancode == 0x48) {
                if (curMenu && curMenu->itemCount > 0) {
                    int32_t idx = ctx->popup.hoverItem;

                    for (int32_t tries = 0; tries < curMenu->itemCount; tries++) {
                        idx--;

                        if (idx < 0) {
                            idx = curMenu->itemCount - 1;
                        }

                        if (!curMenu->items[idx].separator) {
                            break;
                        }
                    }

                    ctx->popup.hoverItem = idx;
                    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY, ctx->popup.popupW, ctx->popup.popupH);
                }

                continue;
            }

            // Down arrow
            if (scancode == 0x50) {
                if (curMenu && curMenu->itemCount > 0) {
                    int32_t idx = ctx->popup.hoverItem;

                    for (int32_t tries = 0; tries < curMenu->itemCount; tries++) {
                        idx++;

                        if (idx >= curMenu->itemCount) {
                            idx = 0;
                        }

                        if (!curMenu->items[idx].separator) {
                            break;
                        }
                    }

                    ctx->popup.hoverItem = idx;
                    dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY, ctx->popup.popupW, ctx->popup.popupH);
                }

                continue;
            }

            // Left arrow — close submenu, or switch to previous top-level menu
            if (scancode == 0x4B) {
                if (ctx->popup.depth > 0) {
                    closePopupLevel(ctx);
                } else {
                    WindowT *win = findWindowById(ctx, ctx->popup.windowId);

                    if (win && win->menuBar && win->menuBar->menuCount > 1) {
                        int32_t newIdx = ctx->popup.menuIdx - 1;

                        if (newIdx < 0) {
                            newIdx = win->menuBar->menuCount - 1;
                        }

                        openPopupAtMenu(ctx, win, newIdx);
                    }
                }

                continue;
            }

            // Right arrow — open submenu, or switch to next top-level menu
            if (scancode == 0x4D) {
                // If hovered item has a submenu, open it
                if (curMenu && ctx->popup.hoverItem >= 0 && ctx->popup.hoverItem < curMenu->itemCount) {
                    MenuItemT *hItem = &curMenu->items[ctx->popup.hoverItem];

                    if (hItem->subMenu && hItem->enabled) {
                        openSubMenu(ctx);
                        continue;
                    }
                }

                // Otherwise switch to next top-level menu
                WindowT *win = findWindowById(ctx, ctx->popup.windowId);

                if (win && win->menuBar && win->menuBar->menuCount > 1) {
                    int32_t newIdx = ctx->popup.menuIdx + 1;

                    if (newIdx >= win->menuBar->menuCount) {
                        newIdx = 0;
                    }

                    openPopupAtMenu(ctx, win, newIdx);
                }

                continue;
            }
        }

        // Enter executes highlighted popup menu item (or opens submenu)
        if (ctx->popup.active && ascii == 0x0D) {
            MenuT *curMenu = ctx->popup.menu;

            if (curMenu && ctx->popup.hoverItem >= 0 && ctx->popup.hoverItem < curMenu->itemCount) {
                MenuItemT *item = &curMenu->items[ctx->popup.hoverItem];

                if (item->subMenu && item->enabled) {
                    openSubMenu(ctx);
                } else if (item->enabled && !item->separator) {
                    int32_t menuId = item->id;
                    WindowT *win   = findWindowById(ctx, ctx->popup.windowId);
                    closeAllPopups(ctx);

                    if (win && win->onMenu) {
                        win->onMenu(win, menuId);
                    }
                }
            } else {
                closeAllPopups(ctx);
            }

            continue;
        }

        // Check for plain key accelerator in open popup menu
        if (ctx->popup.active && ascii != 0) {
            char   lc      = (ascii >= 'A' && ascii <= 'Z') ? (char)(ascii + 32) : (char)ascii;
            MenuT *curMenu = ctx->popup.menu;

            // Try matching an item in the current popup
            if (curMenu) {
                for (int32_t k = 0; k < curMenu->itemCount; k++) {
                    MenuItemT *item = &curMenu->items[k];

                    if (item->accelKey == lc && item->enabled && !item->separator) {
                        if (item->subMenu) {
                            ctx->popup.hoverItem = k;
                            dirtyListAdd(&ctx->dirty, ctx->popup.popupX, ctx->popup.popupY, ctx->popup.popupW, ctx->popup.popupH);
                            openSubMenu(ctx);
                        } else {
                            int32_t menuId = item->id;
                            WindowT *win   = findWindowById(ctx, ctx->popup.windowId);
                            closeAllPopups(ctx);

                            if (win && win->onMenu) {
                                win->onMenu(win, menuId);
                            }
                        }

                        goto nextKey;
                    }
                }
            }

            // No match in current popup — try switching to another top-level menu
            WindowT *win = findWindowById(ctx, ctx->popup.windowId);

            if (win && win->menuBar) {
                for (int32_t i = 0; i < win->menuBar->menuCount; i++) {
                    if (win->menuBar->menus[i].accelKey == lc && i != ctx->popup.menuIdx) {
                        openPopupAtMenu(ctx, win, i);
                        goto nextKey;
                    }
                }
            }
        }

        // ESC closes open dropdown/combobox popup
        if (sOpenPopup && ascii == 0x1B) {
            // Dirty the popup list area
            WindowT *popWin = sOpenPopup->window;
            int32_t  popX;
            int32_t  popY;
            int32_t  popW;
            int32_t  popH;
            widgetDropdownPopupRect(sOpenPopup, &ctx->font, popWin->contentH, &popX, &popY, &popW, &popH);
            dirtyListAdd(&ctx->dirty, popWin->x + popWin->contentX + popX, popWin->y + popWin->contentY + popY, popW, popH);

            WidgetT *closing = sOpenPopup;
            sOpenPopup = NULL;

            if (closing->type == WidgetDropdownE) {
                closing->as.dropdown.open = false;
            } else if (closing->type == WidgetComboBoxE) {
                closing->as.comboBox.open = false;
            }

            wgtInvalidate(closing);
            continue;
        }

        // ESC closes one popup level (or all if at top level)
        if (ctx->popup.active && ascii == 0x1B) {
            closePopupLevel(ctx);
            continue;
        }

        // Check accelerator table on focused window
        if (ctx->stack.focusedIdx >= 0) {
            WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];
            int32_t  key = ascii ? ascii : (scancode | 0x100);

            if (checkAccelTable(ctx, win, key, shiftFlags)) {
                continue;
            }
        }

        // Tab / Shift-Tab — cycle focus between widgets
        // Tab: scancode=0x0F, ascii=0x09
        // Shift-Tab: scancode=0x0F, ascii=0x00
        if (scancode == 0x0F && (ascii == 0x09 || ascii == 0)) {
            if (ctx->stack.focusedIdx >= 0) {
                WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

                if (win->widgetRoot) {
                    // Find currently focused widget
                    WidgetT *current = NULL;
                    WidgetT *fstack[64];
                    int32_t  ftop = 0;
                    fstack[ftop++] = win->widgetRoot;

                    while (ftop > 0) {
                        WidgetT *w = fstack[--ftop];

                        if (w->focused && widgetIsFocusable(w->type)) {
                            // Don't tab out of the terminal — it swallows Tab
                            if (w->type == WidgetAnsiTermE) {
                                current = NULL;
                                break;
                            }

                            current = w;
                            break;
                        }

                        for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
                            if (c->visible && ftop < 64) {
                                fstack[ftop++] = c;
                            }
                        }
                    }

                    // Terminal swallowed Tab — send to widget system instead
                    if (current == NULL) {
                        // Check if a terminal is focused
                        ftop = 0;
                        fstack[ftop++] = win->widgetRoot;
                        bool termFocused = false;

                        while (ftop > 0) {
                            WidgetT *w = fstack[--ftop];

                            if (w->focused && w->type == WidgetAnsiTermE) {
                                termFocused = true;
                                break;
                            }

                            for (WidgetT *c = w->firstChild; c; c = c->nextSibling) {
                                if (c->visible && ftop < 64) {
                                    fstack[ftop++] = c;
                                }
                            }
                        }

                        if (termFocused) {
                            // Terminal has focus — send Tab to it
                            if (win->onKey) {
                                win->onKey(win, ascii ? ascii : (scancode | 0x100), shiftFlags);
                            }

                            continue;
                        }
                    }

                    WidgetT *next;

                    if (ascii == 0x09) {
                        next = widgetFindNextFocusable(win->widgetRoot, current);
                    } else {
                        next = widgetFindPrevFocusable(win->widgetRoot, current);
                    }

                    if (next) {
                        sOpenPopup = NULL;
                        if (sFocusedWidget) {
                            sFocusedWidget->focused = false;
                        }
                        sFocusedWidget = next;
                        next->focused = true;

                        // Scroll the widget into view if needed
                        int32_t scrollX = win->hScroll ? win->hScroll->value : 0;
                        int32_t scrollY = win->vScroll ? win->vScroll->value : 0;
                        int32_t virtX   = next->x + scrollX;
                        int32_t virtY   = next->y + scrollY;

                        if (win->vScroll) {
                            if (virtY < win->vScroll->value) {
                                win->vScroll->value = virtY;
                            } else if (virtY + next->h > win->vScroll->value + win->contentH) {
                                win->vScroll->value = virtY + next->h - win->contentH;
                            }

                            win->vScroll->value = clampInt(win->vScroll->value, win->vScroll->min, win->vScroll->max);
                        }

                        if (win->hScroll) {
                            if (virtX < win->hScroll->value) {
                                win->hScroll->value = virtX;
                            } else if (virtX + next->w > win->hScroll->value + win->contentW) {
                                win->hScroll->value = virtX + next->w - win->contentW;
                            }

                            win->hScroll->value = clampInt(win->hScroll->value, win->hScroll->min, win->hScroll->max);
                        }

                        wgtInvalidate(win->widgetRoot);
                    }
                }
            }

            continue;
        }

        // Send to focused window
        if (ctx->stack.focusedIdx >= 0) {
            WindowT *win = ctx->stack.windows[ctx->stack.focusedIdx];

            if (win->onKey) {
                win->onKey(win, ascii ? ascii : (scancode | 0x100), shiftFlags);
            }
        }

        continue;
nextKey:;
    }
}


// ============================================================
// pollMouse
// ============================================================

static void pollMouse(AppContextT *ctx) {
    __dpmi_regs r;

    memset(&r, 0, sizeof(r));
    r.x.ax = 0x0003;
    __dpmi_int(0x33, &r);

    ctx->mouseX       = r.x.cx;
    ctx->mouseY       = r.x.dx;
    ctx->mouseButtons = r.x.bx;
}


// ============================================================
// refreshMinimizedIcons
// ============================================================
//
// Dirty the next minimized window icon whose content has changed
// since the last refresh. Only considers windows without custom
// iconData. Called every ICON_REFRESH_INTERVAL frames to stagger.

static void refreshMinimizedIcons(AppContextT *ctx) {
    WindowStackT *ws = &ctx->stack;
    DisplayT     *d  = &ctx->display;
    int32_t       count   = 0;
    int32_t       iconIdx = 0;

    for (int32_t i = 0; i < ws->count; i++) {
        WindowT *win = ws->windows[i];

        if (!win->visible || !win->minimized) {
            continue;
        }

        if (!win->iconData && win->contentDirty) {
            if (count >= ctx->iconRefreshIdx) {
                int32_t ix = ICON_SPACING + iconIdx * (ICON_TOTAL_SIZE + ICON_SPACING);
                int32_t iy = d->height - ICON_TOTAL_SIZE - ICON_SPACING;
                dirtyListAdd(&ctx->dirty, ix, iy, ICON_TOTAL_SIZE, ICON_TOTAL_SIZE);
                win->contentDirty   = false;
                ctx->iconRefreshIdx = count + 1;
                return;
            }

            count++;
        }

        iconIdx++;
    }

    // Wrapped past the end — reset for next cycle
    ctx->iconRefreshIdx = 0;
}


// ============================================================
// updateCursorShape
// ============================================================

static void updateCursorShape(AppContextT *ctx) {
    int32_t newCursor = CURSOR_ARROW;
    int32_t mx        = ctx->mouseX;
    int32_t my        = ctx->mouseY;

    // During active resize, keep the resize cursor
    if (ctx->stack.resizeWindow >= 0) {
        int32_t edge = ctx->stack.resizeEdge;
        bool horiz   = (edge & (RESIZE_LEFT | RESIZE_RIGHT)) != 0;
        bool vert    = (edge & (RESIZE_TOP | RESIZE_BOTTOM)) != 0;

        if (horiz && vert) {
            if ((edge & RESIZE_LEFT && edge & RESIZE_TOP) ||
                (edge & RESIZE_RIGHT && edge & RESIZE_BOTTOM)) {
                newCursor = CURSOR_RESIZE_DIAG_NWSE;
            } else {
                newCursor = CURSOR_RESIZE_DIAG_NESW;
            }
        } else if (horiz) {
            newCursor = CURSOR_RESIZE_H;
        } else {
            newCursor = CURSOR_RESIZE_V;
        }
    }
    // Active ListView column resize drag
    else if (sResizeListView) {
        newCursor = CURSOR_RESIZE_H;
    }
    // Active splitter drag
    else if (sDragSplitter) {
        newCursor = sDragSplitter->as.splitter.vertical ? CURSOR_RESIZE_H : CURSOR_RESIZE_V;
    }
    // Not in an active drag/resize — check what we're hovering
    else if (ctx->stack.dragWindow < 0 && ctx->stack.scrollWindow < 0) {
        int32_t hitPart;
        int32_t hitIdx = wmHitTest(&ctx->stack, mx, my, &hitPart);

        if (hitIdx >= 0 && hitPart == 3) {
            // Hovering over a resize edge
            WindowT *win  = ctx->stack.windows[hitIdx];
            int32_t  edge = wmResizeEdgeHit(win, mx, my);
            bool horiz    = (edge & (RESIZE_LEFT | RESIZE_RIGHT)) != 0;
            bool vert     = (edge & (RESIZE_TOP | RESIZE_BOTTOM)) != 0;

            if (horiz && vert) {
                if ((edge & RESIZE_LEFT && edge & RESIZE_TOP) ||
                    (edge & RESIZE_RIGHT && edge & RESIZE_BOTTOM)) {
                    newCursor = CURSOR_RESIZE_DIAG_NWSE;
                } else {
                    newCursor = CURSOR_RESIZE_DIAG_NESW;
                }
            } else if (horiz) {
                newCursor = CURSOR_RESIZE_H;
            } else if (vert) {
                newCursor = CURSOR_RESIZE_V;
            }
        } else if (hitIdx >= 0 && hitPart == 0) {
            // Hovering over content area — check for ListView column border
            WindowT *win = ctx->stack.windows[hitIdx];

            if (win->widgetRoot) {
                int32_t cx = mx - win->x - win->contentX;
                int32_t cy = my - win->y - win->contentY;
                int32_t scrollX = win->hScroll ? win->hScroll->value : 0;
                int32_t scrollY = win->vScroll ? win->vScroll->value : 0;
                int32_t vx = cx + scrollX;
                int32_t vy = cy + scrollY;

                WidgetT *hit = widgetHitTest(win->widgetRoot, vx, vy);

                if (hit && hit->type == WidgetListViewE && widgetListViewColBorderHit(hit, vx, vy)) {
                    newCursor = CURSOR_RESIZE_H;
                }

                // Walk into splitters (NO_HIT_RECURSE stops widgetHitTest at the outermost one)
                while (hit && hit->type == WidgetSplitterE) {
                    int32_t pos = hit->as.splitter.dividerPos;
                    bool onBar;

                    if (hit->as.splitter.vertical) {
                        int32_t barX = hit->x + pos;
                        onBar = (vx >= barX && vx < barX + SPLITTER_BAR_W);
                    } else {
                        int32_t barY = hit->y + pos;
                        onBar = (vy >= barY && vy < barY + SPLITTER_BAR_W);
                    }

                    if (onBar) {
                        newCursor = hit->as.splitter.vertical ? CURSOR_RESIZE_H : CURSOR_RESIZE_V;
                        break;
                    }

                    // Not on this splitter's bar — check children for nested splitters
                    WidgetT *inner = NULL;

                    for (WidgetT *c = hit->firstChild; c; c = c->nextSibling) {
                        if (c->visible && vx >= c->x && vx < c->x + c->w && vy >= c->y && vy < c->y + c->h) {
                            inner = c;
                        }
                    }

                    hit = inner;
                }
            }
        }
    }

    // If cursor shape changed, dirty the cursor area
    if (newCursor != ctx->cursorId) {
        dirtyCursorArea(ctx, mx, my);
        ctx->cursorId = newCursor;
    }
}


// ============================================================
// updateTooltip — show/hide tooltip based on hover state
// ============================================================

static void updateTooltip(AppContextT *ctx) {
    clock_t now       = clock();
    clock_t threshold = (clock_t)TOOLTIP_DELAY_MS * CLOCKS_PER_SEC / 1000;
    int32_t mx        = ctx->mouseX;
    int32_t my        = ctx->mouseY;

    // Mouse moved or button pressed — hide tooltip and reset timer
    if (mx != ctx->prevMouseX || my != ctx->prevMouseY || ctx->mouseButtons) {
        if (ctx->tooltipText) {
            // Dirty old tooltip area
            dirtyListAdd(&ctx->dirty, ctx->tooltipX, ctx->tooltipY, ctx->tooltipW, ctx->tooltipH);
            ctx->tooltipText = NULL;
        }

        ctx->tooltipHoverStart = now;
        return;
    }

    // Already showing a tooltip
    if (ctx->tooltipText) {
        return;
    }

    // Not enough time has passed
    if ((now - ctx->tooltipHoverStart) < threshold) {
        return;
    }

    // Don't show tooltips while popups/menus are active
    if (ctx->popup.active || ctx->sysMenu.active) {
        return;
    }

    // Find the widget under the cursor
    int32_t hitPart;
    int32_t hitIdx = wmHitTest(&ctx->stack, mx, my, &hitPart);

    if (hitIdx < 0 || hitPart != 0) {
        return;
    }

    WindowT *win = ctx->stack.windows[hitIdx];

    if (!win->widgetRoot) {
        return;
    }

    int32_t cx = mx - win->x - win->contentX;
    int32_t cy = my - win->y - win->contentY;
    int32_t scrollX = win->hScroll ? win->hScroll->value : 0;
    int32_t scrollY = win->vScroll ? win->vScroll->value : 0;
    int32_t vx = cx + scrollX;
    int32_t vy = cy + scrollY;

    WidgetT *hit = widgetHitTest(win->widgetRoot, vx, vy);

    // Walk into NO_HIT_RECURSE containers to find deepest child
    while (hit && hit->wclass && (hit->wclass->flags & WCLASS_NO_HIT_RECURSE)) {
        WidgetT *inner = NULL;

        for (WidgetT *c = hit->firstChild; c; c = c->nextSibling) {
            if (c->visible && vx >= c->x && vx < c->x + c->w && vy >= c->y && vy < c->y + c->h) {
                inner = c;
            }
        }

        if (!inner) {
            break;
        }

        // If the inner child has a tooltip, use it; otherwise check if it's another container
        if (inner->tooltip) {
            hit = inner;
            break;
        }

        if (inner->wclass && (inner->wclass->flags & WCLASS_NO_HIT_RECURSE)) {
            hit = inner;
        } else {
            WidgetT *deep = widgetHitTest(inner, vx, vy);
            hit = deep ? deep : inner;
            break;
        }
    }

    if (!hit || !hit->tooltip) {
        return;
    }

    // Show the tooltip
    ctx->tooltipText = hit->tooltip;

    int32_t tw = textWidth(&ctx->font, hit->tooltip) + TOOLTIP_PAD * 2;
    int32_t th = ctx->font.charHeight + TOOLTIP_PAD * 2;

    // Position below and right of cursor
    ctx->tooltipX = mx + 12;
    ctx->tooltipY = my + 16;

    // Keep on screen
    if (ctx->tooltipX + tw > ctx->display.width) {
        ctx->tooltipX = ctx->display.width - tw;
    }

    if (ctx->tooltipY + th > ctx->display.height) {
        ctx->tooltipY = my - th - 4;
    }

    ctx->tooltipW = tw;
    ctx->tooltipH = th;

    // Dirty the tooltip area
    dirtyListAdd(&ctx->dirty, ctx->tooltipX, ctx->tooltipY, tw, th);
}