DVX_GUI/dvx

DV/X GUI

A DESQview/X-style windowed GUI compositor for DOS, targeting DJGPP/DPMI with VESA VBE 2.0+ linear framebuffer.

Motif-style beveled chrome, dirty-rectangle compositing, draggable and resizable windows, dropdown menus, scrollbars, and a declarative widget/layout system with buttons, checkboxes, radios, text inputs, dropdowns, combo boxes, sliders, spinners, progress bars, tab controls, tree views, list views, scroll panes, toolbars, status bars, images, image buttons, drawable canvases, password inputs, masked/formatted inputs, and an ANSI BBS terminal emulator.

Building

Requires the DJGPP cross-compiler (i586-pc-msdosdjgpp-gcc).

The GUI is built as a static library (lib/libdvx.a). The demo links against it.

cd dvxdemo
make            # builds lib/libdvx.a then bin/demo.exe
make clean      # removes obj/ and bin/

Set DJGPP_PREFIX in the Makefile if your toolchain is installed somewhere other than ~/djgpp/djgpp.

Architecture

The library is organized in five layers. Each layer is a .h/.c pair. Application code only needs to include dvxApp.h (which pulls in the rest) and optionally dvxWidget.h.

Layer 1  dvxVideo   VESA init, LFB mapping, backbuffer, pixel format
Layer 2  dvxDraw    Spans, rects, bevels, text, bitmaps (asm inner loops)
Layer 3  dvxComp    Dirty rectangle list, merge, LFB flush
Layer 4  dvxWm      Window stack, chrome, drag, resize, focus, menus, scrollbars
Layer 5  dvxApp     Event loop, mouse/keyboard input, public API
         dvxWidget  Widget/layout system (optional, standalone)

Supporting files:

File	Purpose
dvxTypes.h	Shared type definitions used by all layers
dvxFont.h	Built-in 8x14 bitmap font glyph data
dvxCursor.h	Mouse cursor bitmask data (5 shapes)
dvxPalette.h	Default VGA palette for 8-bit mode
dvxIcon.c	stb_image implementation unit (BMP/PNG/JPEG/GIF)
dvxImageWrite.c	stb_image_write implementation unit (PNG export)
thirdparty/stb_image.h	Third-party single-header image loader
thirdparty/stb_image_write.h	Third-party single-header image writer

The widget system lives in widgets/:

File	Purpose
widgets/widgetInternal.h	Shared internal header: vtable type, constants, cross-widget prototypes
widgets/widgetClass.c	Widget class table: one WidgetClassT vtable entry per widget type
widgets/widgetCore.c	Allocation, tree ops, hit testing, flag-based type queries
widgets/widgetLayout.c	Two-pass layout engine (measure + arrange)
widgets/widgetEvent.c	Mouse, keyboard, scroll, resize, and paint event dispatch
widgets/widgetOps.c	Paint dispatcher, public operations (wgtFind, wgtDestroy, etc.)
widgets/widget*.c	One file per widget type (button, checkbox, slider, etc.)

Each widget type is self-contained in its own .c file. Dispatch for paint, layout, mouse, keyboard, getText/setText, and destroy is driven by a per-type vtable (WidgetClassT) rather than switch statements in the core files. Adding a new widget type requires only a new .c file and an entry in the class table.

Quick start

#include "dvxApp.h"

static void onPaint(WindowT *win, RectT *dirty) {
    AppContextT *ctx = (AppContextT *)win->userData;
    const BlitOpsT *ops = dvxGetBlitOps(ctx);
    const DisplayT *d   = dvxGetDisplay(ctx);
    uint32_t blue = packColor(d, 0, 0, 200);

    for (int32_t y = 0; y < win->contentH; y++) {
        ops->spanFill(win->contentBuf + y * win->contentPitch,
                      blue, win->contentW);
    }
}

int main(void) {
    AppContextT ctx;

    if (dvxInit(&ctx, 1024, 768, 16) != 0) {
        return 1;
    }

    WindowT *win = dvxCreateWindow(&ctx, "Hello", 100, 100, 300, 200, true);
    win->userData = &ctx;
    win->onPaint  = onPaint;

    RectT r = {0, 0, win->contentW, win->contentH};
    win->onPaint(win, &r);

    dvxRun(&ctx);
    dvxShutdown(&ctx);

    return 0;
}

Quick start (widgets)

#include "dvxApp.h"
#include "dvxWidget.h"

static void onButtonClick(WidgetT *w) {
    WidgetT *root = w;
    while (root->parent) root = root->parent;

    WidgetT *lbl = wgtFind(root, "status");
    if (lbl) {
        wgtSetText(lbl, "Clicked!");
        wgtInvalidate(lbl);
    }
}

int main(void) {
    AppContextT ctx;
    dvxInit(&ctx, 1024, 768, 16);

    WindowT *win = dvxCreateWindow(&ctx, "Widgets", 100, 100, 260, 200, true);
    win->userData = &ctx;

    WidgetT *root = wgtInitWindow(&ctx, win);

    WidgetT *lbl = wgtLabel(root, "Ready.");
    strncpy(lbl->name, "status", MAX_WIDGET_NAME);

    wgtHSeparator(root);

    WidgetT *row = wgtHBox(root);
    wgtLabel(row, "Name:");
    wgtTextInput(row, 64);

    WidgetT *btn = wgtButton(root, "Go");
    btn->onClick = onButtonClick;

    wgtInvalidate(root);   // initial layout + paint

    dvxRun(&ctx);
    dvxShutdown(&ctx);

    return 0;
}

---

Application API (dvxApp.h)

Lifecycle

int32_t dvxInit(AppContextT *ctx, int32_t requestedW, int32_t requestedH,
                int32_t preferredBpp);

Initialize VESA video, input, fonts, color scheme, and cursors. Finds a mode matching the requested resolution and bit depth (8, 15, 16, or 32). Returns 0 on success, -1 on failure.

void dvxRun(AppContextT *ctx);

Enter the main event loop. Handles mouse movement, button clicks, keyboard input, window management, dirty-rectangle compositing, and LFB flush. Returns when dvxQuit() is called or ESC is pressed.

bool dvxUpdate(AppContextT *ctx);

Process one iteration of the event loop: poll input, dispatch events, composite dirty regions, and flush. Returns true if the GUI is still running, false when exit has been requested. Use this instead of dvxRun() when embedding the GUI inside an existing main loop.

void dvxShutdown(AppContextT *ctx);

Restore text mode, release LFB mapping, and free the backbuffer.

void dvxQuit(AppContextT *ctx);

Request exit from the main loop. dvxRun() returns on the next iteration.

Windows

WindowT *dvxCreateWindow(AppContextT *ctx, const char *title,
                          int32_t x, int32_t y, int32_t w, int32_t h,
                          bool resizable);

Create a window at screen position (x, y) with outer dimensions w x h. If resizable is true, the window gets resize handles and a maximize button. The window is raised to the top and given focus. Returns NULL on failure.

After creation, set win->userData and install callbacks:

Callback	Signature	When called
onPaint	void (WindowT *win, RectT *dirtyArea)	Content needs redrawing
onKey	void (WindowT *win, int32_t key, int32_t mod)	Key press (focused window)
onMouse	void (WindowT *win, int32_t x, int32_t y, int32_t buttons)	Mouse event in content area
onResize	void (WindowT *win, int32_t newW, int32_t newH)	Window resized
onClose	void (WindowT *win)	Close button double-clicked
onMenu	void (WindowT *win, int32_t menuId)	Menu item selected
onScroll	void (WindowT *win, ScrollbarOrientE orient, int32_t value)	Scrollbar moved

Mouse/key coordinates are relative to the content area. buttons is a bitmask (bit 0 = left, bit 1 = right, bit 2 = middle).

void dvxDestroyWindow(AppContextT *ctx, WindowT *win);

Remove a window from the stack and free its resources.

void dvxSetTitle(AppContextT *ctx, WindowT *win, const char *title);

Change the title bar text.

int32_t dvxSetWindowIcon(AppContextT *ctx, WindowT *win, const char *path);

Load a BMP, TGA, or PNG image and assign it as the window's minimized icon. The image is converted to the display pixel format and scaled to 64x64. Returns 0 on success.

Invalidation

void dvxInvalidateRect(AppContextT *ctx, WindowT *win,
                        int32_t x, int32_t y, int32_t w, int32_t h);
void dvxInvalidateWindow(AppContextT *ctx, WindowT *win);

Mark a region (or the entire content area) as needing repaint. The compositor flushes dirty rectangles to the LFB on the next frame.

Accessors

DisplayT         *dvxGetDisplay(AppContextT *ctx);
const BlitOpsT   *dvxGetBlitOps(const AppContextT *ctx);
const BitmapFontT *dvxGetFont(const AppContextT *ctx);
const ColorSchemeT *dvxGetColors(const AppContextT *ctx);

Window properties

Set these directly on the WindowT struct after creation:

Field	Type	Default	Description
maxW	int32_t	-1	Maximum width when maximized (-1 = screen width)
maxH	int32_t	-1	Maximum height when maximized (-1 = screen height)
userData	void *	NULL	Application data pointer, passed through to callbacks

Content buffer

Each window has a persistent content backbuffer:

Field	Description
contentBuf	Pixel data in display format
contentPitch	Bytes per scanline
contentW	Width in pixels
contentH	Height in pixels

Paint callbacks write directly into contentBuf. The compositor copies visible portions to the screen backbuffer, then flushes dirty rects to the LFB.

---

Menu bars

MenuBarT *wmAddMenuBar(WindowT *win);

Add a menu bar to a window. Call wmUpdateContentRect() and wmReallocContentBuf() after adding the menu bar (the menu bar reduces the content area).

MenuT *wmAddMenu(MenuBarT *bar, const char *label);

Add a top-level menu to the bar. Returns a MenuT * to populate with items.

void wmAddMenuItem(MenuT *menu, const char *label, int32_t id);
void wmAddMenuSeparator(MenuT *menu);

Add items to a menu. id is an application-defined command passed to onMenu. Up to 16 items per menu, 8 menus per bar.

---

Scrollbars

ScrollbarT *wmAddVScrollbar(WindowT *win, int32_t min, int32_t max,
                             int32_t pageSize);
ScrollbarT *wmAddHScrollbar(WindowT *win, int32_t min, int32_t max,
                             int32_t pageSize);

Add a scrollbar to a window. pageSize controls the thumb size relative to the range. Call wmUpdateContentRect() and wmReallocContentBuf() afterward.

The onScroll callback fires when the user drags the thumb or clicks the arrow buttons / trough.

Widget windows manage their own scrollbars automatically -- do not add them manually.

---

Video and drawing (dvxVideo.h, dvxDraw.h)

These are lower-level APIs. Application code typically only needs packColor.

uint32_t packColor(const DisplayT *d, uint8_t r, uint8_t g, uint8_t b);

Pack an RGB triple into the display's pixel format.

void rectFill(DisplayT *d, const BlitOpsT *ops,
              int32_t x, int32_t y, int32_t w, int32_t h, uint32_t color);

Fill a rectangle with a solid color (clipped to the display clip rect).

void drawBevel(DisplayT *d, const BlitOpsT *ops,
               int32_t x, int32_t y, int32_t w, int32_t h,
               const BevelStyleT *style);

Draw a beveled frame. BevelStyleT specifies highlight, shadow, face colors and border width.

void drawText(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font,
              int32_t x, int32_t y, const char *text,
              uint32_t fg, uint32_t bg, bool opaque);
int32_t drawChar(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font,
                 int32_t x, int32_t y, char ch,
                 uint32_t fg, uint32_t bg, bool opaque);
int32_t textWidth(const BitmapFontT *font, const char *text);

Draw text using the built-in 8-pixel-wide bitmap font. opaque controls whether background pixels are drawn. drawChar returns the advance width.

void drawTermRow(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font,
                 int32_t x, int32_t y, int32_t cols,
                 const uint8_t *lineData, const uint32_t *palette,
                 bool blinkVisible, int32_t cursorCol);

Bulk-render a row of terminal character cells. lineData points to (char, attr) byte pairs (2 bytes per cell). palette is a 16-entry packed-color table. blinkVisible controls blink attribute visibility. cursorCol is the column to draw inverted (-1 for no cursor). This is much faster than calling drawChar per cell because clip bounds are computed once for the whole row and there is no per-character function call overhead.

char accelParse(const char *text);

Parse an accelerator key from text with & markers (e.g. "E&xit" returns 'x'). Returns the lowercase accelerator character, or 0 if none found.

void drawTextAccel(DisplayT *d, const BlitOpsT *ops, const BitmapFontT *font,
                   int32_t x, int32_t y, const char *text,
                   uint32_t fg, uint32_t bg, bool opaque);
int32_t textWidthAccel(const BitmapFontT *font, const char *text);

Draw/measure text with & accelerator processing. The character after & is underlined. && produces a literal &. textWidthAccel returns the width in pixels, excluding & markers.

void drawFocusRect(DisplayT *d, const BlitOpsT *ops,
                   int32_t x, int32_t y, int32_t w, int32_t h,
                   uint32_t color);

Draw a dotted rectangle outline (every other pixel). Used to indicate keyboard focus on widgets.

void drawMaskedBitmap(DisplayT *d, const BlitOpsT *ops,
                      int32_t x, int32_t y, int32_t w, int32_t h,
                      const uint16_t *andMask, const uint16_t *xorData,
                      uint32_t fgColor, uint32_t bgColor);

Draw a 1-bit bitmap with AND/XOR masks (used for mouse cursors). Each row is a uint16_t. Pixels where the AND mask is 0 are drawn using the XOR data to select fgColor or bgColor.

void drawHLine(DisplayT *d, const BlitOpsT *ops,
               int32_t x, int32_t y, int32_t w, uint32_t color);
void drawVLine(DisplayT *d, const BlitOpsT *ops,
               int32_t x, int32_t y, int32_t h, uint32_t color);

void rectCopy(DisplayT *d, const BlitOpsT *ops,
              int32_t dstX, int32_t dstY,
              const uint8_t *srcBuf, int32_t srcPitch,
              int32_t srcX, int32_t srcY, int32_t w, int32_t h);

Blit from a source buffer to the backbuffer with clipping.

void setClipRect(DisplayT *d, int32_t x, int32_t y, int32_t w, int32_t h);
void resetClipRect(DisplayT *d);

---

Widget system (dvxWidget.h)

An optional declarative layout system inspired by Amiga MUI and PC GEOS. Widgets are arranged in a tree of VBox/HBox containers. A two-pass layout engine (measure minimum sizes, then distribute space) handles geometry automatically. Scrollbars appear when the window is too small for the content.

Initialization

WidgetT *wgtInitWindow(AppContextT *ctx, WindowT *win);

Attach the widget system to a window. Returns the root container (a VBox filling the content area). Installs onPaint, onMouse, onKey, and onResize handlers on the window. Build the widget tree by passing the returned root (or its children) as parent to the widget creation functions below.

Call wgtInvalidate(root) after the tree is fully built to trigger the initial layout and paint.

Containers

WidgetT *wgtVBox(WidgetT *parent);    // vertical stack
WidgetT *wgtHBox(WidgetT *parent);    // horizontal stack
WidgetT *wgtFrame(WidgetT *parent, const char *title);  // titled border

Containers hold child widgets and control layout direction. wgtFrame draws a styled border with a title label and lays out children vertically.

Frame styles (set w->as.frame.style after creation):

Style	Description
FrameInE	Beveled inward / sunken (default)
FrameOutE	Beveled outward / raised
FrameFlatE	Solid color line; set w->as.frame.color (0 = windowShadow)

The title text is vertically centered on the top border line.

Container properties (set directly on the returned WidgetT *):

Field	Type	Default	Description
align	WidgetAlignE	AlignStartE	Main-axis alignment when no children have weight
spacing	int32_t	0 (4px)	Tagged size: gap between children
padding	int32_t	0 (4px)	Tagged size: internal padding

Alignment values:

Value	HBox meaning	VBox meaning
AlignStartE	left	top
AlignCenterE	center	center
AlignEndE	right	bottom

Widgets

WidgetT *wgtLabel(WidgetT *parent, const char *text);

Static text label. Sized to fit its text.

WidgetT *wgtButton(WidgetT *parent, const char *text);

Beveled push button with standard press/release behavior: the button visually depresses on mouse-down, tracks the cursor while held, and fires onClick on release if still over the button. Dragging off the button cancels the click.

WidgetT *wgtCheckbox(WidgetT *parent, const char *text);

Toggle checkbox. Read/write w->as.checkbox.checked. Set onChange to be notified.

WidgetT *wgtRadioGroup(WidgetT *parent);
WidgetT *wgtRadio(WidgetT *parent, const char *text);

Radio buttons with diamond-shaped indicators (visually distinct from checkboxes). Create a group, then add options as children. The group tracks the selected index in w->as.radioGroup.selectedIdx. Set onChange on the group to be notified. Radio indices are auto-assigned.

WidgetT *wgtTextInput(WidgetT *parent, int32_t maxLen);

Single-line text input field. maxLen is the buffer capacity. Default weight is 100 (stretches to fill). Set onChange to be notified on edits.

Editing features: cursor movement (arrows, Home, End), insert/overwrite, selection (Shift+arrows, Shift+Home/End, Ctrl+A, double-click word, triple-click all), clipboard (Ctrl+C copy, Ctrl+V paste, Ctrl+X cut), single-level undo (Ctrl+Z), and horizontal scrolling when text exceeds the visible width. Mouse drag selection auto-scrolls when the cursor reaches the edge of the field.

WidgetT *wgtPasswordInput(WidgetT *parent, int32_t maxLen);

Password input field. Identical to wgtTextInput except characters are displayed as bullets (CP437 \xF9). Copy and cut to clipboard are disabled; paste is allowed. All other editing features work normally.

WidgetT *wgtMaskedInput(WidgetT *parent, const char *mask);

Formatted input field with a fixed mask pattern. The mask string defines the format: # accepts a digit, A accepts a letter, * accepts any printable character. All other characters in the mask are literals that are displayed but cannot be edited. The cursor skips over literal positions automatically.

Example masks:

• "(###) ###-####" -- US phone number
• "##/##/####" -- date
• "###-##-####" -- SSN

The buffer always contains the full formatted text including literals. wgtGetText() returns the formatted string. Supports selection (Shift+arrows, Ctrl+A), clipboard (Ctrl+C, Ctrl+V, Ctrl+X), and single-level undo (Ctrl+Z). The mask string must remain valid for the widget's lifetime.

WidgetT *wgtListBox(WidgetT *parent);

List box (basic -- set items with wgtListBoxSetItems()).

WidgetT *wgtTextArea(WidgetT *parent, int32_t maxLen);

Multi-line text editor with vertical and horizontal scrollbars. Supports all the same editing features as wgtTextInput plus multi-line selection (Shift+Up/Down), Enter for newlines, and vertical/horizontal auto-scroll during mouse drag selection. A horizontal scrollbar appears automatically when any line exceeds the visible width. The vertical scrollbar is always present.

Dropdown and ComboBox

WidgetT *wgtDropdown(WidgetT *parent);
void     wgtDropdownSetItems(WidgetT *w, const char **items, int32_t count);
int32_t  wgtDropdownGetSelected(const WidgetT *w);
void     wgtDropdownSetSelected(WidgetT *w, int32_t idx);

Non-editable selection widget. Clicking the arrow button opens a popup list below (or above if no room). Clicking the arrow again while the popup is open closes it. Set onChange to be notified of selection changes. The items array must remain valid for the widget's lifetime.

WidgetT *wgtComboBox(WidgetT *parent, int32_t maxLen);
void     wgtComboBoxSetItems(WidgetT *w, const char **items, int32_t count);
int32_t  wgtComboBoxGetSelected(const WidgetT *w);
void     wgtComboBoxSetSelected(WidgetT *w, int32_t idx);

Editable text field with a dropdown list. The text area accepts keyboard input (same editing keys as wgtTextInput). Clicking the arrow button toggles the popup; clicking the text area focuses it for editing. Selecting an item copies its text into the edit buffer. Default weight is 100.

ProgressBar and Slider

WidgetT *wgtProgressBar(WidgetT *parent);
void     wgtProgressBarSetValue(WidgetT *w, int32_t value);
int32_t  wgtProgressBarGetValue(const WidgetT *w);

Horizontal progress indicator. Value is 0--100 (percentage). The filled portion draws left-to-right with the system highlight color.

WidgetT *wgtSlider(WidgetT *parent, int32_t minVal, int32_t maxVal);
void     wgtSliderSetValue(WidgetT *w, int32_t value);
int32_t  wgtSliderGetValue(const WidgetT *w);

Draggable slider/trackbar. Horizontal by default; set w->as.slider.vertical = true after creation for vertical orientation. The thumb tracks the mouse while held. Set onChange to be notified.

Spinner

WidgetT *wgtSpinner(WidgetT *parent, int32_t minVal, int32_t maxVal, int32_t step);
void     wgtSpinnerSetValue(WidgetT *w, int32_t value);
int32_t  wgtSpinnerGetValue(const WidgetT *w);
void     wgtSpinnerSetRange(WidgetT *w, int32_t minVal, int32_t maxVal);
void     wgtSpinnerSetStep(WidgetT *w, int32_t step);

Numeric up/down input field with increment/decrement buttons. The text area accepts direct keyboard entry of digits (and minus sign when the minimum is negative). Up/Down arrows increment/decrement by step; Page Up/Page Down by step * 10. Enter commits the typed value; Escape reverts. The value is clamped to [minVal, maxVal] on every change.

Supports all single-line text editing features: cursor movement, selection (Shift+arrows, Ctrl+A, double/triple-click), clipboard (Ctrl+C/V/X), and single-level undo (Ctrl+Z). Non-numeric input is filtered out.

The widget has a sunken text area with up/down arrow buttons on the right. Clicking the top half of the button area increments; the bottom half decrements. Set onChange to be notified of value changes.

TabControl

WidgetT *wgtTabControl(WidgetT *parent);
WidgetT *wgtTabPage(WidgetT *parent, const char *title);
void     wgtTabControlSetActive(WidgetT *w, int32_t idx);
int32_t  wgtTabControlGetActive(const WidgetT *w);

Tabbed container. Create a tab control, then add pages as children. Each page is a VBox that holds its own widget subtree. Only the active page is visible and receives layout; inactive pages are hidden. Clicking a tab header switches the active page.

StatusBar and Toolbar

WidgetT *wgtStatusBar(WidgetT *parent);
WidgetT *wgtToolbar(WidgetT *parent);

Horizontal containers with specialized chrome. StatusBar draws a sunken panel background; Toolbar draws a raised background. Both use horizontal layout with default spacing. Add child widgets (labels, buttons, etc.) as with any HBox. StatusBar children with weight > 0 stretch to fill.

TreeView

WidgetT *wgtTreeView(WidgetT *parent);
WidgetT *wgtTreeItem(WidgetT *parent, const char *text);
void     wgtTreeItemSetExpanded(WidgetT *w, bool expanded);
bool     wgtTreeItemIsExpanded(const WidgetT *w);
WidgetT *wgtTreeViewGetSelected(const WidgetT *w);
void     wgtTreeViewSetSelected(WidgetT *w, WidgetT *item);

Hierarchical tree with expand/collapse support. Create a tree view, then add items as children. Nest items by adding them as children of other items. Items with children show a [+]/[-] expand box.

The tree view manages its own internal scrollbars: a vertical scrollbar appears when expanded items exceed the visible height, and a horizontal scrollbar appears when item text extends beyond the visible width. Both scrollbars have arrow buttons, proportional thumbs, and page scrolling on trough clicks.

Default weight is 100. Set onClick on individual tree items to handle selection, or onChange to be notified of expand/collapse.

wgtTreeViewGetSelected returns the currently selected tree item (or NULL). wgtTreeViewSetSelected sets the selection programmatically.

Image

WidgetT *wgtImage(WidgetT *parent, uint8_t *data,
                   int32_t w, int32_t h, int32_t pitch);
WidgetT *wgtImageFromFile(WidgetT *parent, const char *path);
void     wgtImageSetData(WidgetT *w, uint8_t *data,
                          int32_t imgW, int32_t imgH, int32_t pitch);

Display a bitmap image. wgtImage takes ownership of the pixel buffer (freed on destroy). wgtImageFromFile loads any format supported by stb_image and converts to the display pixel format. Set onClick to make the image clickable.

ImageButton

WidgetT *wgtImageButton(WidgetT *parent, uint8_t *data,
                         int32_t w, int32_t h, int32_t pitch);
void     wgtImageButtonSetData(WidgetT *w, uint8_t *data,
                                int32_t imgW, int32_t imgH, int32_t pitch);

Push button that displays an image instead of a text caption. Behaves identically to wgtButton -- visually depresses on mouse-down, tracks the cursor while held, and fires onClick on release if still over the button. The image is centered on the button face with a 2px bevel border and no extra padding. When pressed, the image shifts 1px down and right.

wgtImageButton takes ownership of the pixel buffer (freed on destroy). wgtImageButtonSetData replaces the image data, freeing the previous buffer. The pixel buffer must be in display pixel format (use packColor() and the display's bytesPerPixel to prepare it).

Canvas

WidgetT *wgtCanvas(WidgetT *parent, int32_t w, int32_t h);

Drawable bitmap canvas with a sunken bevel border. Supports both interactive freehand drawing (mouse strokes are Bresenham-interpolated) and programmatic drawing from the API.

void    wgtCanvasClear(WidgetT *w, uint32_t color);
void    wgtCanvasSetPenColor(WidgetT *w, uint32_t color);
void    wgtCanvasSetPenSize(WidgetT *w, int32_t size);
int32_t wgtCanvasSave(WidgetT *w, const char *path);
int32_t wgtCanvasLoad(WidgetT *w, const char *path);

wgtCanvasSave writes the canvas to a PNG file (converting from display pixel format to RGB). wgtCanvasLoad reads any image format supported by stb_image and converts it to display pixel format.

Programmatic drawing primitives (all coordinates are in canvas space):

void     wgtCanvasSetPixel(WidgetT *w, int32_t x, int32_t y, uint32_t color);
uint32_t wgtCanvasGetPixel(const WidgetT *w, int32_t x, int32_t y);
void     wgtCanvasDrawLine(WidgetT *w, int32_t x0, int32_t y0, int32_t x1, int32_t y1);
void     wgtCanvasDrawRect(WidgetT *w, int32_t x, int32_t y, int32_t width, int32_t height);
void     wgtCanvasFillRect(WidgetT *w, int32_t x, int32_t y, int32_t width, int32_t height);
void     wgtCanvasFillCircle(WidgetT *w, int32_t cx, int32_t cy, int32_t radius);

SetPixel/GetPixel take explicit colors. DrawLine uses the current pen color and pen size. DrawRect draws a 1px outline, FillRect fills solid, and FillCircle fills a circle -- all using the current pen color. All operations clip to the canvas bounds. Colors are in display pixel format (use packColor() to create them).

ANSI Terminal

WidgetT *wgtAnsiTerm(WidgetT *parent, int32_t cols, int32_t rows);

ANSI BBS terminal emulator widget. Displays a character grid (default 80x25 if cols/rows are 0) with full ANSI escape sequence support and a 16-color CGA palette. The terminal has a 2px sunken bevel border and a vertical scrollbar for scrollback history. Supports mouse text selection (click and drag), Ctrl+C to copy selected text (sends ^C to the terminal when nothing is selected), and Ctrl+V to paste clipboard text through the comm interface.

ANSI escape sequences supported:

Sequence	Description
ESC[H / ESC[f	Cursor position (CUP/HVP)
ESC[A/B/C/D	Cursor up/down/forward/back
ESC[J	Erase display (0=to end, 1=to start, 2=all)
ESC[K	Erase line (0=to end, 1=to start, 2=all)
ESC[m	SGR: colors 30-37/40-47, bright 90-97/100-107, bold(1), blink(5), reverse(7), reset(0)
ESC[s / ESC[u	Save / restore cursor position
ESC[S / ESC[T	Scroll up / down
ESC[L / ESC[M	Insert / delete lines
ESC[?7h/l	Enable / disable auto-wrap
ESC[?25h/l	Show / hide cursor

Control characters: CR, LF, BS, TAB, BEL (ignored).

void wgtAnsiTermWrite(WidgetT *w, const uint8_t *data, int32_t len);

Feed data through the ANSI parser. Use this to display .ANS files or inject content without a communications link.

void wgtAnsiTermClear(WidgetT *w);

Clear the screen, push all visible lines to scrollback, and reset the cursor to the home position.

void wgtAnsiTermSetComm(WidgetT *w, void *ctx,
                         int32_t (*readFn)(void *, uint8_t *, int32_t),
                         int32_t (*writeFn)(void *, const uint8_t *, int32_t));

Set the communications interface. readFn should return bytes read (0 if none available). writeFn sends bytes. Pass NULL function pointers for a disconnected / display-only terminal.

When connected, keyboard input is translated to ANSI sequences and sent via writeFn (arrows become ESC[A..ESC[D, etc.).

int32_t wgtAnsiTermPoll(WidgetT *w);

Poll the comm interface for incoming data and process it through the ANSI parser. Also handles cursor blink and text blink timers. Returns the number of bytes read. When using dvxUpdate(), terminal polling is handled automatically -- call this manually only when running your own event loop.

int32_t wgtAnsiTermRepaint(WidgetT *w, int32_t *outY, int32_t *outH);

Fast repaint: renders only dirty rows directly into the window's content buffer, bypassing the full widget paint pipeline (no clear, no relayout, no other widgets). Returns the number of rows repainted (0 if nothing was dirty). If outY and outH are non-NULL, they receive the content-buffer-relative Y coordinate and height of the repainted region, for targeted dirty-rect invalidation. Uses drawTermRow() internally for efficient bulk rendering. When using dvxUpdate(), this is called automatically after wgtAnsiTermPoll().

void wgtAnsiTermSetScrollback(WidgetT *w, int32_t maxLines);

Set the scrollback buffer size (default 500 lines). Clears any existing scrollback. Lines scroll into the buffer when they leave the top of the screen or when the screen is cleared (ESC[2J / wgtAnsiTermClear).

A vertical scrollbar appears automatically when there is scrollback content. Click the arrow buttons for single-line scrolling, or the trough for page scrolling. The view auto-follows live output unless the user has scrolled back.

Spacing and dividers

WidgetT *wgtSpacer(WidgetT *parent);

Invisible spacer. Default weight is 100 -- pushes siblings apart.

WidgetT *wgtHSeparator(WidgetT *parent);   // horizontal line
WidgetT *wgtVSeparator(WidgetT *parent);   // vertical line

Visual divider lines (shadow + highlight, 2px).

Size specifications

Size fields (minW, minH, maxW, maxH, prefW, prefH, spacing, padding) accept tagged values created with:

wgtPixels(120)     // 120 pixels
wgtChars(15)       // 15 character widths
wgtPercent(50)     // 50% of parent

A raw 0 means auto (use the widget's natural/computed size).

Weight

The weight field controls how extra space is distributed among siblings. When a container is larger than its children's combined minimum size, the surplus is divided proportionally by weight.

• weight = 0 -- fixed size, does not stretch (default for most widgets)
• weight = 100 -- normal stretch (default for spacers and text inputs)
• Relative values work: weights of 100, 200, 100 give a 1:2:1 split

When all children have weight 0, the container's align property determines where children are placed within the extra space.

Operations

void wgtSetText(WidgetT *w, const char *text);
const char *wgtGetText(const WidgetT *w);

Get/set text for labels, buttons, checkboxes, radios, text inputs, password inputs, masked inputs, combo boxes, and dropdowns.

void wgtSetEnabled(WidgetT *w, bool enabled);
void wgtSetVisible(WidgetT *w, bool visible);

Disabled widgets are drawn grayed out and ignore input. Hidden widgets are excluded from layout.

void wgtInvalidate(WidgetT *w);

Trigger a full relayout and repaint of the widget tree. Call after modifying widget properties, adding/removing widgets, or changing text.

WidgetT *wgtFind(WidgetT *root, const char *name);

Search the subtree for a widget by name. Set w->name (up to 31 chars) to make a widget findable.

void wgtDestroy(WidgetT *w);

Remove a widget and all its children from the tree and free memory.

void wgtSetDebugLayout(bool enabled);

When enabled, draws 1px neon-colored borders around all layout containers so their bounds are visible. Each container gets a distinct color derived from its pointer.

Layout and paint internals

These are called automatically by wgtInvalidate(), but are available for manual use when embedding the widget system in a custom event loop.

int32_t wgtResolveSize(int32_t taggedSize, int32_t parentSize, int32_t charWidth);

Convert a tagged size (from wgtPixels, wgtChars, or wgtPercent) to a pixel value given the parent's size and the font's character width.

void wgtLayout(WidgetT *root, int32_t availW, int32_t availH,
               const BitmapFontT *font);

Run the two-pass layout engine on the widget tree: measure minimum sizes bottom-up, then distribute available space top-down. Sets x, y, w, h on every widget.

void wgtPaint(WidgetT *root, DisplayT *d, const BlitOpsT *ops,
              const BitmapFontT *font, const ColorSchemeT *colors);

Paint the entire widget tree into the window's content buffer.

List box operations

void    wgtListBoxSetItems(WidgetT *w, const char **items, int32_t count);
int32_t wgtListBoxGetSelected(const WidgetT *w);
void    wgtListBoxSetSelected(WidgetT *w, int32_t idx);

ListView

WidgetT *wgtListView(WidgetT *parent);
void     wgtListViewSetColumns(WidgetT *w, const ListViewColT *cols, int32_t count);
void     wgtListViewSetData(WidgetT *w, const char **cellData, int32_t rowCount);
int32_t  wgtListViewGetSelected(const WidgetT *w);
void     wgtListViewSetSelected(WidgetT *w, int32_t idx);

Multi-column list with sortable headers, resizable columns, and single or multi-select support. Column definitions use ListViewColT:

typedef struct {
    const char      *title;
    int32_t          width;    // tagged size (wgtPixels/wgtChars/wgtPercent)
    ListViewAlignE   align;    // ListViewAlignLeftE, CenterE, or RightE
} ListViewColT;

Column widths support tagged sizes (wgtPixels, wgtChars, wgtPercent). Cell data is a flat array of strings in row-major order (row0col0, row0col1, ..., row1col0, ...). Both the column and data arrays must remain valid for the widget's lifetime.

Clicking a column header sorts the list. An arrow indicator shows the current sort direction. Column borders can be dragged to resize. Vertical and horizontal scrollbars appear automatically when needed.

void wgtListViewSetSort(WidgetT *w, int32_t col, ListViewSortE dir);
void wgtListViewSetHeaderClickCallback(WidgetT *w,
         void (*cb)(WidgetT *w, int32_t col, ListViewSortE dir));

Programmatic sort control. The header click callback fires after the sort direction is updated, allowing custom sort logic.

void wgtListViewSetMultiSelect(WidgetT *w, bool multi);
bool wgtListViewIsItemSelected(const WidgetT *w, int32_t idx);
void wgtListViewSetItemSelected(WidgetT *w, int32_t idx, bool selected);
void wgtListViewSelectAll(WidgetT *w);
void wgtListViewClearSelection(WidgetT *w);

Multi-select mode supports Ctrl+click to toggle individual items and Shift+click for range selection. Default weight is 100.

ScrollPane

WidgetT *wgtScrollPane(WidgetT *parent);

Scrollable container for child widgets. Children are laid out vertically (like a VBox) at their natural size. Vertical and horizontal scrollbars appear automatically when the content exceeds the visible area.

Mouse clicks on the scrollbar arrows scroll by one line/character; clicks on the trough scroll by one page. Clicks on the content area are forwarded to child widgets. Keyboard scrolling: Up/Down arrows, Page Up/Down, Home/End for vertical; Left/Right arrows for horizontal.

Set padding and spacing to control internal layout. Default weight is 100.

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Types reference (dvxTypes.h)

WindowT

Core window structure. Key fields:

Field	Type	Description
id	int32_t	Unique window identifier
x, y, w, h	int32_t	Outer frame position and size
contentX, contentY	int32_t	Content area offset within frame
contentW, contentH	int32_t	Content area dimensions
contentBuf	uint8_t *	Pixel buffer (display format)
contentPitch	int32_t	Bytes per scanline in content buffer
title	char[128]	Title bar text
visible	bool	Window is shown
focused	bool	Window has input focus
minimized	bool	Window is minimized to icon
maximized	bool	Window is maximized
resizable	bool	Window has resize handles
maxW, maxH	int32_t	Max dimensions for maximize (-1 = screen)
userData	void *	Application data pointer

ColorSchemeT

All colors are pre-packed via packColor():

Field	Usage
desktop	Desktop background
windowFace	Window frame fill
windowHighlight	Bevel light edge
windowShadow	Bevel dark edge
activeTitleBg/Fg	Focused title bar
inactiveTitleBg/Fg	Unfocused title bar
contentBg/Fg	Window content area
menuBg/Fg	Menu bar and popups
menuHighlightBg/Fg	Highlighted menu item
buttonFace	Button interior
scrollbarBg/Fg/Trough	Scrollbar elements

BitmapFontT

Fixed-width bitmap font (8px wide, 14 or 16px tall). Glyphs are packed 1bpp, charHeight bytes per glyph, MSB-first.

BevelStyleT

typedef struct {
    uint32_t highlight;   // top/left edge color
    uint32_t shadow;      // bottom/right edge color
    uint32_t face;        // interior fill (0 = no fill)
    int32_t  width;       // border thickness in pixels
} BevelStyleT;

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Window chrome

Windows use a Motif/GEOS-style frame:

• 4px beveled outer border with perpendicular groove breaks
• 20px title bar (dark charcoal background when focused)
• Close button on the left edge (requires double-click)
• Minimize button on the right edge (always present)
• Maximize button to the left of minimize (resizable windows only)
• Optional menu bar below the title bar (20px)
• Optional scrollbars along the right and bottom edges (16px)

Minimized windows appear as 64x64 beveled icons along the bottom of the screen. If a window has an icon image set via dvxSetWindowIcon(), that image is shown; otherwise a nearest-neighbor-scaled thumbnail of the window's content buffer is used. Thumbnails are refreshed automatically when the window's content changes, with updates staggered across frames so only one icon redraws per interval. Double-click an icon to restore.

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Hardware requirements

• 486 or later CPU
• VESA VBE 2.0+ compatible video card with linear framebuffer support
• PS/2 mouse (or compatible mouse driver)
• DPMI host (CWSDPMI, Windows DOS box, DOSBox, 86Box)

Tested on 86Box with PCI video cards. DOSBox is a trusted reference platform.