Fixes the O(file)-per-keystroke slowness that made large-file editing
unusable. pmacs-gpu now shapes only the visible byte slice instead of
the whole rope.
Core change (`reshape`): compute the visible byte range from
`scroll_top` + the window's visible line count (+ small overscan),
slice `current_text[vstart..vend]`, clip+rebase spans / decorations /
adornments onto the slice (subtract `vstart`), and feed only that to
`set_rich_text`. cosmic-text now touches ~screenful of lines, not 25k.
`set_rich_text` resets scroll to the slice top (verified), so the
slice renders from y=0.
Scroll (line-based, Q#S1):
- `scroll_top` source-line state; `visible_byte_range` line-aligns the
slice (cosmic-text splits BufferLines on `\n`).
- `scroll_to_cursor` (Q#S2): on `CursorByte`, if the cursor leaves the
visible window, scroll to follow, re-shape, and re-declare the scoped
Viewport. PageUp/Down already forward → daemon moves the cursor →
this follows. No GPU-local page math.
- Scoped `Viewport` declaration (Q#S5) via `viewport_send_if_changed`
(coalesced): on snapshot, scroll, edit (bytes shift), and resize. The
producer already clips `StyleSpans`/`Decorations` to `vp.visible`, so
it now styles only what's on screen — no producer change.
Rebasing (bet S2, the QB3-class risk): one primitive,
`clip_rebase_range`, clips a whole-file `[start,end)` to the slice and
subtracts `vstart`, returning `None` when disjoint. Caret
(`caret_rect`) and both wash collectors route through it; `line_offsets`
are computed on the slice. Caret returns `None` when scrolled
off-screen.
Also resets `scroll_top` + `last_viewport_sent` on buffer switch.
Tests: `clip_rebase_range_clips_to_slice_and_subtracts_vstart`.
Gates: fmt; clippy --all-targets --workspace -D warnings; pmacs-gpu
unit 23 (+1). Daemon/lib untouched.
Per the framing's process rule, NOT merged until visually confirmed on
a large file AND after scrolling (the rebasing is only exercised once
vstart > 0): editing snappy; arrows/PageUp/PageDown navigate with the
caret staying visible; styling + caret correct at any scroll position;
TUI stays converged.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Levi Neuwirth
ecb0a862fc