A pin jumps over whatever part of a glyph's reservation the font did not
cover, and nothing wrote that cell. prompt_toolkit never writes the cell
after a wide glyph either, since it counts it as the glyph's own, so a
repaint that put an emoji where two letters had been left the second letter
standing beside it on a terminal that draws the emoji in one cell. On the
fast path the row is erased first, but only in the default colours, so the
same cell was a hole in a chip's fill.
Both pins now erase the reservation in the current colours before drawing
the glyph, with ECH, which blanks cells without moving the cursor.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
The rows the fast renderer writes were already pinned. Anything
prompt_toolkit lays out itself — a floating dialog, and the backdrop it
repaints — still went out through its differential renderer, which steps a
cursor of its own by each glyph's measured width and moves relatively from
there, so one glyph drawn at another width threw off every move after it.
That renderer never knows a column absolutely, so the pin is spelled
relative to the glyph instead: save the cursor, draw the glyph, restore,
step forward exactly the width the renderer is about to add. The terminal's
cursor is back in step after every glyph, and nothing is tracked that could
drift from the renderer's own bookkeeping. PinnedOutput wraps the real
terminal; the width reclaim stays outermost.
A flag's two indicators are now merged into one cell before layout, like a
ZWJ sequence, so the pair is written as one glyph rather than with a cursor
move between its halves.
Nothing is pinned on a platform that draws no emoji: the PicoCalc only ever
draws glyphs its own font has verified.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Alignment stopped depending on the width tables being right about a glyph.
After anything whose drawn width is not certain, a row now carries an
absolute column address naming the column the app measured that glyph
into, so a mismeasured emoji costs one cell inside its own lane instead
of every lane after it and the frame's right border.
The curated narrow/wide sets keep their job — they are what makes the
reservation right, so a listed glyph gets neither a gap nor an overwrite
— but they are no longer what holds a row together. A name off the air,
which nobody can put on a list in advance, now frames flush too.
Pinning only where it is needed: the ranges the app draws in bulk and both
authorities agree are one cell (box drawing, braille, blocks, the node
marks, the chevrons) are listed, and a row holding nothing else is handed
back untouched — one scan, no walk. That list is a performance claim, not
what correctness rests on; getting an entry wrong costs what today costs.
Proved against a terminal that disagrees on purpose rather than against a
measurement, since the disagreement is the thing that cannot be probed.
Still limited to the rows the fast renderer writes itself: a frame
prompt_toolkit lays out — a dialog, and the backdrop it repaints — tracks
the cursor in its own arithmetic and is uncorrected. MESHTERM_COLUMN_SNAP=0
turns it off.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Jean-Pierre MartineauandClaude Opus 5