feat: click or drag a hidden window's edge slice to reach it#157

Summary

With displays side by side, #155 shows a hidden window's slice as a live photo on the edge the displays share. On stacked displays you can click a hidden window's sliver to reach it. This PR makes the photo slice clickable too, step 5 of #150.

This branch pins engine b741dfc, the merged head of samanyudas/paneru#81. The branch was rebased before its merge, so b741dfc has the same tree as the tested e30ba61. The change:

• A click on the slice focuses its window, scrolls it into view, and reaches the app on the clicked row, 12 points inside the window's edge. The pointer moves to that point.
• A drag that starts on the slice continues in the app.
• A fast double click acts as one click. A click never reaches the window beside the slice.
• Scrolling and hovering over the slice do nothing.

docs/limitations.md now says what a click and a drag do, that the pointer jumps, and that scroll and hover do nothing. PROGRESS.md records the live checks and the fixes they led to.

Stacked on #155.

Related issues

Part of #150

Verification

• Live on Sam's Mac, 29 October, displays side by side, engine c99fbe8, on an AppKit view and a Chromium page:

  • Quick clicks with releases 30 to 150 ms after the press arrived as one press and release at one point, 12 points inside the edge.
  • A 30 ms double click arrived as one click, and a 50 ms double click as a real double click.
  • A drag delivered all 20 moves and its release.
  • Hover and scroll did nothing, and the window beside the slice got nothing.

• The first live run found that the exact clicked point lands on the window's resize border, where the app gets nothing. Sam chose the 12-point inset. The second found a quick click's release arriving at the slice's old position, which is now moved with the press.

• The three later engine fixes guard event reorders that did not happen live. Harness tests cover them. Details are in paneru#81.

• make engine-lint, engine cargo test --no-default-features (1048, 42, and 1), make docs, make swift-lint, make build, and swift test (167 tests) pass.

• make lint passes except compat, which needs the engine stack on the fork's miri/v0.5.2.

• make check passes locally, or the skipped targets are named with the reason. Skipped e2e, because the live checks above replace it, and compat, which waits on the engine stack.

• Behavior that unit tests cannot show was checked end to end, and the observed output is above. Not checked live: the reorder cases the last three engine fixes guard.

• PROGRESS.md reflects the state after this PR.

Release

With displays side by side, clicking or dragging a hidden window's slice on the edge next to the other display brings that window into view and passes the click to it.

Reviewed with sol-loop: 5 rounds with gpt-6.1-sol on high. Sol verdict: approved

Started by a GPT-6.1 Sol continuation in T3 Code. Finished with Claude Opus 5.5 in Claude Code.

🤖 Generated with Claude Code