fix(app): keep pointer events within window bounds

[besmpl]

Summary

• gate ordinary mouse moves and legacy/detailed wheel events to the window's logical bounds while retaining held-button capture outside the window
• use detailed scroll coordinates/modifiers where available, preserve platform compatibility fallbacks, and deduplicate leave/callback delivery
• reset mouse-only capture, pressed, hover, and cursor state on focus loss or pointer cancellation without letting touch/pen mutate legacy mouse state
• enforce ListView's drawable content X band, excluding the scrollbar inset
• add regressions for bounds, HiDPI coordinates, capture/cancellation, zero-value windows, and ListView edges

Why

Pointer events can arrive after the cursor leaves a native window. Passing ordinary moves and wheel events through caused stale hover/selection/scroll behavior, while simply dropping every outside event would break legitimate captured drags. The bridge now distinguishes those cases at the shared boundary and cleans up incomplete pointer sequences when focus is lost.

Verification

• go test ./... -count=1
• CGO_ENABLED=0 go build ./...
• go build ./...
• go vet ./app/... ./event/... ./core/listview/...
• focused event/ListView tests repeated 20×
• focused race tests
• gofmt and git diff --check

A pre-existing test-only race in TestWindow_AnimPumper_StartsOnInvalidation still prevents a clean full go test -race ./...; the changed focused packages expose no new race.

Fixes #179

Local CI and Codecov preflight

• rebased onto current main (273cc1e)
• go test ./... -count=1: pass
• focused changed-package race suite: pass; the repository-wide race suite remains blocked only by the pre-existing TestWindow_AnimPumper_StartsOnInvalidation mock race noted above
• go build ./..., go vet ./..., gofmt, and diff checks: pass
• local Codecov-equivalent changed-production coverage: 137/137 statements (100%) (app/event_bridge.go 92/92, app/window.go 31/31, core/listview/event.go 14/14); overall coverage 86.4%

Upstream CI run approval is still external to this branch: GitHub marked the fork workflow action_required with zero jobs. A gogpu maintainer must approve the workflow before Actions and the configured Codecov upload/bot can run.

Review follow-up (2026-08-12)

Extracted mouse-button ownership tracking into the private trackMouseButtonOwnership helper, reducing HandleEvent below the configured cyclomatic-complexity limit without changing event ordering.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[kolkov]

REQUEST CHANGES (1 lint issue)

Strong work on event handling. The gate logic is correct: handleBridgeMouseMove drops ordinary moves when outside window bounds with no buttons held, but preserves captured drags. Synthetic MouseLeave with leaveDispatched deduplication is well-designed. Focus-loss cancellation via cancelPointerState delivers synthetic releases per button at an outside-widget position.

Coverage is excellent: 137/137 changed statements (100%), ~65% of added lines are tests. The TestWindow_FocusLossCancelsSliderDrag end-to-end test against real slider.New is particularly good.

Lint failure (blocking):

• app/window.go:417 -- HandleEvent cyclomatic complexity = 22 (threshold 20). Extract the early button-ownership tracking block into a private helper method (e.g., trackButtonOwnership or updateMouseButtonState).

After the gocyclo fix, this is ready to merge.

[kolkov]

Lint fix confirmed — HandleEvent complexity resolved by extracting pointInWindow and handleBridgeMouseMove helpers. CI 9/9 pass. APPROVE.