Retires the first half of Phase A's deferred finding A8 (background-
bearing decoration kinds couldn't render through cosmic-text's
foreground-only `Attrs`). `DecorationKind::Selection` now paints a
translucent blue rectangle under the selected glyphs in pmacs-gpu,
reusing the wgpu `QuadRenderer` that shipped for the minimap in
session 7.
The framing doc (`docs/pmacs-gpu-quad-backgrounds-framing.md`)
commits the load-bearing decisions before code lands: stance (α)
for Q#2 — single render pass, three draws in the order backgrounds
→ text → minimap — is what this commit implements. Q#1 (CurrentLine
source location, stance α: producer-side from
`core.active_window_for(self.frontend_id).cursor`) and Q#3 (per-line
cadence, stance β) are sketched for session 9.2; Q#4 defers search
backgrounds awaiting an upstream pmacs search feature.
Three components:
1. `decoration_kind_to_bg_color` helper, sibling of the existing
`decoration_kind_to_color`. Returns `Some([f32; 4])` RGBA for
Selection; `None` for CurrentLine (9.2), SearchMatch /
SearchMatchActive (deferred), and the four diagnostic kinds
(foreground-only). New unit tests assert disjoint total cover
between the two helpers across the eight kinds.
2. `State::decoration_background_rects` walks
`Buffer::layout_runs()`, finds glyphs whose `[start, end)`
overlaps each background-bearing decoration's `ByteRange`, and
produces one `MinimapRect` per laid-out visual line that
contributes glyphs. Multi-line selections fan out as N rects.
3. Render-order change in `State::render`: a `bg_buffer` is built
ahead of the minimap buffer and drawn first in the render pass
(before `text_renderer.render`), so selection fills sit under
the glyphs with the 0.30-alpha letting source color show through.
Minimap continues to draw last.
Gates green:
- cargo fmt --all -- --check
- cargo clippy --all-targets --workspace -- -D warnings
- cargo clippy --all-targets --workspace --features crdt -- -D warnings
- pmacs-gpu unit: 13 (+2 new bg-color helper tests)
- pmacs lib: 1325, pmacs-protocol: 11
- m4_acceptance: 88, m11_5_semantic_acceptance (--features crdt): 2
Bet exercise so far: bet #1 (multi-line vertex decomposition) is
implicitly tested by the layout-run loop but waits on visual
validation for honest scoring. Bet #2 (overlap composition) is not
exercised in 9.1 — Selection is the only background kind, so no
overlaps with CurrentLine or future kinds. Bet #3 (cadence) is a
9.2 concern.
Manual probe: launch daemon + TUI attach + pmacs-gpu attach against
any file, select text in the TUI, verify the pmacs-gpu window paints
a translucent blue rectangle over the selected glyphs that tracks
selection extension. Multi-line selection should produce per-visual-
line rectangles.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
Levi Neuwirth
54991c89e4