TERMINAL_CELL_WIDTH was 8.4 — a number nobody had measured. Asking the text
system for the advance of `0` in the face actually being painted gives ~7.3, so
the guess was 13% wide and the terminal was losing eighteen columns: the same
window that reported 122 columns now reports 140. Layout and paint now read the
same measurement, so they cannot drift apart again.
The plan claimed ws_xpixel disagreed with the painted width by 0.4 px per
column. It did not: the app only ever called TerminalSize::new, which passes no
pixel dimensions, so ws_xpixel and ws_ypixel were both *zero*. Every program
doing pixel arithmetic — sixel, the kitty graphics protocol, anything sizing an
image to the viewport — was being told the window has no size at all. Both the
spawn and the resize paths now report the real extent.
TerminalDimensions gains cell_width/cell_height accessors: it was already
carrying the values and nothing could read them.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
