DVX_GUI/README.md

# 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.

## 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 |

## Quick start

```c
#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)

```c
#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

```c
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.

```c
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.

```c
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.

```c
void dvxShutdown(AppContextT *ctx);
```
Restore text mode, release LFB mapping, and free the backbuffer.

```c
void dvxQuit(AppContextT *ctx);
```
Request exit from the main loop. `dvxRun()` returns on the next iteration.

### Windows

```c
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).

```c
void dvxDestroyWindow(AppContextT *ctx, WindowT *win);
```
Remove a window from the stack and free its resources.

```c
void dvxSetTitle(AppContextT *ctx, WindowT *win, const char *title);
```
Change the title bar text.

```c
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

```c
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

```c
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

```c
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).

```c
MenuT *wmAddMenu(MenuBarT *bar, const char *label);
```
Add a top-level menu to the bar. Returns a `MenuT *` to populate with items.

```c
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

```c
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`.

```c
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.

```c
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).

```c
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.

```c
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.

```c
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);
```

```c
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.

```c
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

```c
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

```c
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

```c
WidgetT *wgtLabel(WidgetT *parent, const char *text);
```
Static text label. Sized to fit its text.

```c
WidgetT *wgtButton(WidgetT *parent, const char *text);
```
Beveled push button. Set `onClick` to handle clicks.

```c
WidgetT *wgtCheckbox(WidgetT *parent, const char *text);
```
Toggle checkbox. Read/write `w->as.checkbox.checked`. Set `onChange` to
be notified.

```c
WidgetT *wgtRadioGroup(WidgetT *parent);
WidgetT *wgtRadio(WidgetT *parent, const char *text);
```
Radio buttons. 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.

```c
WidgetT *wgtTextInput(WidgetT *parent, int32_t maxLen);
```
Single-line text input field. Supports typing, cursor movement (arrows,
Home, End), backspace, and delete. `maxLen` is the buffer capacity.
Default weight is 100 (stretches to fill). Set `onChange` to be notified
on edits.

```c
WidgetT *wgtListBox(WidgetT *parent);
```
List box (basic -- set items with `wgtListBoxSetItems()`).

```c
WidgetT *wgtTextArea(WidgetT *parent, int32_t maxLen);
```
Multi-line text area (basic).

### Canvas

```c
WidgetT *wgtCanvas(WidgetT *parent, int32_t w, int32_t h);
```
Drawable bitmap canvas with a sunken bevel border. Supports freehand
drawing with Bresenham-interpolated strokes.

```c
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.

### Spacing and dividers

```c
WidgetT *wgtSpacer(WidgetT *parent);
```
Invisible spacer. Default weight is 100 -- pushes siblings apart.

```c
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:

```c
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

```c
void wgtSetText(WidgetT *w, const char *text);
const char *wgtGetText(const WidgetT *w);
```
Get/set text for labels, buttons, checkboxes, radios, and text inputs.

```c
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.

```c
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.

```c
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.

```c
void wgtDestroy(WidgetT *w);
```
Remove a widget and all its children from the tree and free memory.

```c
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.

### List box operations

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

---

## 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

```c
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;
```

---

## 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.

---

## 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.