# tvision-m2 - milestone summary (2026-09-16)

A TVision/Turbo-Vision style character-cell UI toolkit written in ISO GNU
Modula-2 (`gm2 -fiso`) for the terminal, developed alongside the tigr and
microui bindings in this repository.  No C source and no graphics
dependency; the only non-Modula-2 part is the libc binding `tvtty.def`.

## Status

Working milestone: a retained view tree with clipping and z-order, a diffed
ANSI screen, keyboard + mouse input, widgets and modal dialogs.  Builds
warning-free and was exercised by driving a real pty (frames reconstructed
from the captured terminal stream).

## Files

| file | role |
|---|---|
| `tvtty.def` | libc binding: raw mode, winsize, read/write |
| `tv.def` / `tv.mod` | screen, view tree, widgets, events, modal dialog |
| `demo.mod` | demo application (two windows, all widgets, mouse) |
| `ttysize.mod` | diagnostic for the tty binding |
| `Makefile` | build |
| `README.md` | build/run + API + GM2 notes |

## Implemented

- Alternate screen, hidden/show cursor, terminal restore on exit.
- 16-colour fg/bg, explicit blink on/off, UTF-8 box drawing, clipping stack.
- Diffed redraw: only changed cells are written.
- View tree: groups and windows own children; per-window clipping; z-order
  with click-to-front; windows draggable by the title row (any direction) and
  clamped so the title stays on screen; ` X ` close box.
- Widgets: static text, frame, input line (insert/backspace/delete/Home/End/
  arrows), push button, check box, radio buttons, list box (selection, wheel
  scroll) and vertical scroll bar.
- Focus chain (Tab / Shift-Tab / up-down); hardware cursor in the focused
  input; Enter/Space activate.
- Keyboard decoding: printable UTF-8, arrows, Home/End, PgUp/PgDn, Ins/Del,
  F1-F12, Enter, Space, Backspace, Esc, Ctrl-C.
- Mouse: xterm SGR reporting (mode 1002/1006) - click to focus/press, drag
  titles, click list rows, wheel scroll.
- Modal `Message` dialog with its own event loop.
- Menu bar with drop-down menus: click or `F10` to open, Left/Right switch
  menus, Up/Down move, Enter/Space or click selects (returns the item tag);
  separators supported.

## Verified

Driving the demo through a pty and reconstructing the screen:
- initial layout (Editor + About windows, list, radios, check box, buttons,
  status bar) renders correctly;
- clicking `OK` with the mouse opens the modal Info box;
- dragging the title moves the window in every direction and clamps at the
  top-left so the title stays visible;
- clicking the `File` title opens the drop-down (New/Open/Sep/Quit), `F10`
  + Enter selects the first item (status shows the command tag), and
  clicking `Quit` exits the program.

## Known limitations / next steps

- `Message` is the only dialog helper; no generic form dialog.
- Menu items have no hotkeys; no check/radio menu items.
- Windows are not resizable; no hover highlight.
- Terminal size is polled (no `SIGWINCH`-driven relayout).
- Nested clipping groups beyond windows are untested.

## GNU Modula-2 notes

See `README.md`: value-returning no-arg procedures need `()` in the `.def`;
pointer fields need `^`; a `BEGIN...END` block cannot be a `CASE` branch;
`INTEGER` vs `HIGH()` comparisons need `VAL`; termios/winsize use fixed Linux
offsets.  A subtle runtime bug was found and fixed in the ANSI output: SGR
attributes accumulate, so blink must be emitted explicitly as `;5`/`;25` or
it leaks into every following cell.