Tigr-m2/tvision-m2

tvision-m2 - a TVision/Turbo-Vision style toolkit in GNU Modula-2

A character-cell UI toolkit written in ISO GNU Modula-2 (gm2 -fiso) that runs in a terminal (xterm and friends). It is a small, self-contained Turbo-Vision-like library: a retained view tree with clipping and z-order, a diffed ANSI cell screen, keyboard and mouse decoding (xterm SGR mouse reports), widgets, and modal dialogs.

Everything is Modula-2 except tvtty.def, the tiny libc binding used to put the terminal in raw mode and to query its size (termios, ioctl, read, write). There is no C source and no graphics dependency.

Files

file	role
tvtty.def	libc binding (raw mode, winsize, read/write)
tv.def / tv.mod	the toolkit: screen, view tree, widgets, events
demo.mod	demo application
ttysize.mod	diagnostic: checks the tty binding

Build & run

gm2 -fiso -c tvtty.def
gm2 -fiso -I. -c tv.mod
gm2 -fiso -I. tv.o demo.mod -o demo
./demo

or simply make. Run it from a real terminal; Esc exits.

What works

• Alternate screen, hidden/show cursor, terminal restored on exit.
• 16-colour foreground/background with blink; UTF-8 output (box-drawing).
• Perspective view tree: groups and windows contain children; drawing is clipped to each window; overlapping windows are ordered (z-order) and the one you click comes to the front.
• Windows: double-line frame, title, X close box, draggable by the title bar with the mouse.
• Widgets: static text, single/double frame, input line (insert, backspace, delete, Home/End/arrows), push button, check box, radio buttons, list box with selection and wheel scrolling, vertical scroll bar.
• Focus chain: Tab/Shift-Tab and up/down cycle widgets; the focused input gets the hardware cursor.
• Keyboard decoding: printable UTF-8, arrows, Home/End, PgUp/PgDn, Ins/Del, Tab/Shift-Tab, F1-F12, Enter, Space, Backspace, Esc, Ctrl-C.
• Mouse: xterm SGR reporting - click to focus/press, drag window titles, click list rows, wheel-scroll lists.
• Diffed redraw (only changed cells are written).
• Modal dialog helper (Message), used by the demo's OK button.

Roadmap ideas

• Drop-down menus and a menu-bar widget.
• Modal Dialog with arbitrary controls; form validation.
• Nested clipping groups and a desktop with many windows / tiling.
• More widgets: multi-line editor, tabs, combo box, progress bar.
• SIGWINCH-driven relayout (today the app polls the size).
• Mouse hover highlight and resizable windows.

GNU Modula-2 notes

• Value-returning procedures with no parameters need explicit () (PROCEDURE Cols() : INTEGER;), otherwise the .def fails to parse when compiled through the .mod.
• Pointer fields require ^ (v^.rect); there is no implicit dereference.
• A compound BEGIN ... END block is not a statement, so it cannot appear directly in a CASE alternative - use a helper procedure.
• An INTEGER index compared with HIGH(array) (a CARDINAL) must be converted: i <= VAL(INTEGER, HIGH(a)).
• The libc struct termios/struct winsize are accessed through an opaque byte buffer with fixed Linux offsets (see tv.mod).