#446 chunk B: Hit-test chrome surfaces (tab bars, status bars, breadcrumbs)

[JDonaghy]

Sub-task of #446 — Migrate GTK draw wiring to ScreenLayout::draw()

Scope (chunk 2 of 4): Chrome surfaces with hit-test

Migrate surfaces that require cached layout for click dispatch. These broke in the first attempt because b.X_layout() didn't match the rasteriser's geometry.

Surfaces:

• Tab bars (single-group + multi-group) — needs TabBarHits for slot positions, close bounds, right-segment bounds, correct_scroll_offset
• Per-window status bars — needs StatusBarLayout for segment click dispatch
• Breadcrumb bars — needs StatusBarLayout for segment hit regions
• Debug toolbar — StatusBar variant, verify hit-test

Prerequisite: quadraui#211 must land first — rasterisers need to consume their own layout so paint and hit-test agree.

Branch: continue on issue-446-screen-layout-draw after chunk A merges.

Depends on

• #446 chunk A: Scaffolding + paint-only surfaces (no hit-test) #460 (chunk A — scaffolding)
• quadraui#211 (rasteriser-consumes-layout refactor)

Related

• Parent: Migrate GTK draw wiring to quadraui ScreenLayout::draw() #446
• Previous chunk: #446 chunk A: Scaffolding + paint-only surfaces (no hit-test) #460
• Next chunk: #446 chunk B: Hit-test chrome surfaces (tab bars, status bars, breadcrumbs) #461 (complex surfaces)

[JDonaghy]

Pausing on quadraui#213

WIP committed on issue-461-hit-test-chrome-surfaces branch. All 4 surfaces migrated:

• Tab bars (draw_tab_bar helper)
• Breadcrumb (draw_breadcrumb_bar helper)
• Per-window status (draw_window_status_bar helper)
• Debug toolbar (draw_debug_toolbar helper)

Smoke test partial:

• Tab clicks + close button ✓ (post-GTK debug panel: variable tree clicks land on row ~2 above the clicked one #211 geometry alignment did its job)
• Tab overflow scroll-into-view ✗ — tab_bar_layout() returns resolved_scroll_offset rather than the rasteriser's fit_active_scroll_offset for active-tab visibility. Filed quadraui#213.

Breadcrumb, per-window status, debug toolbar are migrated but not yet smoke-tested — paused on quadraui#213 since same backend's _layout() symmetry guarantees apply.

Resume once quadraui#213 ships. Branch left at WIP commit; DO NOT MERGE.

[JDonaghy]

Now blocked on quadraui#215 (separate gap from #213)

Smoke after quadraui#213 landed:

• Tab clicks + close ✓
• Tab overflow scroll-into-view ✓ (quadraui#213 fix did the job)
• Breadcrumb click hit-test ✗ — clicking the filename segment lands in a symbol's hit region; clicking a symbol does nothing

Filed quadraui#215. Root cause: status_bar_layout measures with self.pango_ctx (vimcode's UI font, set at startup) while the rasteriser measures with cr's pango layout (editor monospace inside draw_editor). Tab bars and debug toolbar happen to work because vimcode's helpers explicitly swap cr's font to UI_FONT before drawing. Breadcrumbs and per-window status bars don't swap — and never needed to under the old direct-call-with-return pattern.

Per-window status bar likely has the same latent bug but wasn't smoke-tested yet.

Branch issue-461-hit-test-chrome-surfaces stays at WIP commit 8e2d863. Resume when quadraui#215 ships.

[JDonaghy]

Findings — what this migration needed and what it surfaced

PR #466 lands the 4-surface migration. Getting here required three quadraui follow-up fixes beyond the initial `_layout()` methods from quadraui#210:

1. quadraui#211 — GTK rasterisers (`gtk::draw_tab_bar`, `gtk::draw_activity_bar`) needed to consume `bar.layout()` directly so paint and the new `_layout()` methods share one geometry source. Closed by quadraui PR #212.
2. quadraui#213 — `tab_bar_layout()` discarded the `fit_active_scroll_offset` computation that the rasteriser did post-`bar.layout()`. Without that, opening a new tab off-screen didn't trigger scroll-into-view reconciliation. Closed by quadraui PR #214.
3. quadraui#215 — `_layout()` methods measured via `self.pango_ctx` (set once at startup) while rasterisers measured via the frame-scope cr's pango layout. Vimcode sets `self.pango_ctx` to UI sans-serif but paints breadcrumbs / per-window status with editor monospace — so segment hit_regions drifted relative to where paint actually drew. Closed by quadraui PR #216.

The lesson loop: quadraui#210 introduced the `_layout()` methods. Each subsequent quadraui issue patched a different way those methods diverged from the rasteriser. The current state ("rasteriser consumes layout + layout uses frame-scope pango") is the contract that makes Surface-push migrations safe.

Spin-off (vimcode-side, not quadraui)

• #465 — clicking a breadcrumb symbol segment opens an empty symbol picker. Pre-existing, in `core::engine::picker::breadcrumb_open_scoped` (engine code, untouched by this PR). Likely a `breadcrumb_scoped_parent` filter mismatch or symbol-extraction issue. Was hidden before because filename clicks were misrouted into the symbol picker — quadraui#215 fixed the routing, exposing the underlying empty-picker bug. Filed as vimcode, not quadraui, since the engine-side picker population is the suspect.

[JDonaghy]

Landed in PR #466 (merged).