# microui port to GNU Modula-2 - summary (2026-09-16)

An ISO Modula-2 port of **microui v2.02** (immediate-mode UI by rxi, MIT),
built with the existing tigr binding, plus a tigr-rendered demo.

## Files

| file | role |
|---|---|
| `microui.def` | public API: types, constants, widgets |
| `microui.mod` | full port of `microui.c` (core, layout, widgets, command list) |
| `microuiHelpers.def/.mod` | bit ops, memory/string helpers, `%f`/`%g` number formatting |
| `examples/microui-demo/microui-demo.mod` | interactive demo (mouse/keyboard, tigr renderer) |
| `examples/microui-demo/microui-headless.mod` | off-screen smoke test -> `microui-demo.png` |
| `examples/microui-demo/microui-demo.png` | reference screenshot |

The upstream C sources are vendored in `microui-master/`.

## Build

From `modula2/`:

    gcc -c ../tigr-master/tigr.c -o tigr.o
    gm2 -fiso -c helper.mod
    gm2 -fiso -I. -c microuiHelpers.mod
    gm2 -fiso -I. -c microui.mod

From `modula2/examples/microui-demo/`:

    gm2 -fiso -I ../../ ../../tigr.o ../../helper.o \
         ../../microuiHelpers.o ../../microui.o \
         microui-demo.mod -o microui-demo -lGL -lX11
    gm2 -fiso -I ../../ ../../tigr.o ../../helper.o \
         ../../microuiHelpers.o ../../microui.o \
         microui-headless.mod -o microui-headless -lGL -lX11

## Run

    ./microui-demo        # window; ESC quits
    ./microui-headless    # writes microui-demo.png

## What works (verified)

Windows, title bars, close/resize handles, headers, tree nodes, buttons,
checkboxes, sliders, number fields, text boxes, panels, popups, scroll bars,
word-wrapped `text`, clipping, z-ordering and hover/focus tracking. The demo
was run under X11 and the headless test renders an identical layout to PNG.

## Design adaptations

- The C `mu_Command` union is represented by a `BaseCommand` header and
  concrete command records, accessed with `CAST(CommandPtr, ...)`.
- Callbacks are invoked through one-argument records (`TextWidthArgs`,
  `TextHeightArgs`, `FrameArgs`).
- `drawText` takes an `ADDRESS` + length so substrings need no copy.
- tigr's `tigrFillRect` fills only the *interior* of a rectangle
  (`x+1, y+1, w-2, h-2`); a filled microui rectangle is therefore drawn as
  `tigrRect` (1px outline) + `tigrFillRect` (interior). Using `tigrFillRect`
  alone shrinks every rect by one pixel and makes all 1px borders (window and
  control outlines) disappear.
- The demo window uses `TIGR_AUTO`: tigr resizes the bitmap to match the
  window (1:1), so the framebuffer is never cropped or letterboxed and
  resizing works like a normal resizable window. Forcing a scale with
  `TIGR_2X` crops the bitmap when it doesn't fit the screen (that cut the
  window title row), and `TIGR_FIXED` letterboxes it. The renderer uses
  `bmp^.w`/`bmp^.h` for its clip and clear.

## GNU Modula-2 16.0.1 issues worked around

See `ANALYSIS.md` for the full list. Highlights:

- Procedure types accept only a single unnamed formal parameter when the
  `.def` is parsed as part of the `.mod`.
- Inline `POINTER TO T` is rejected in formal parameter lists and in `CAST`;
  named pointer aliases are used instead.
- `SHORTREAL(integer)` is miscompiled to `0`; conversions go through `FLOAT`
  (`microuiHelpers.IntToReal`/`CardToReal`).
- `TRUNC` rejects values whose type is a type alias (`Real = SHORTREAL`);
  `ROUND` is undefined; `EXIT` is only allowed inside `LOOP`.
- `ADDRESS` has no `+` (use `ADDADR`); function results cannot be dereferenced
  directly or discarded.