Codex Step 3 R1 BLOCK: the prior fix `10cae1e5` exposed
canvas_height() on WebBackend but only used it for the white-
background clear, NOT for `WidgetHost::paint`. The host's
canvas viewport rect still derived its height from a hardcoded
`640.0` (web) / `600.0` (native), so any window/canvas at a
non-default height got the wrong bottom edge.
Fix: extend both `paint` signatures to accept
`viewport_height: f32` and replace the hardcoded
`640.0 - rail_top_y` / `600.0 - rail_top_y` expressions with
`(viewport_height - rail_top_y).max(0.0)`.
Web side:
- `widget_host.rs::WidgetHost::paint(backend, viewport_width,
viewport_height)` — `// glue:` marker preserved on the
signature line.
- `lib.rs::paint_inspector` reads BOTH `viewport_w` and
`viewport_h` from the backend and forwards them to
`host.paint`.
Native side:
- `widget_host.rs::WidgetHostNative::paint(frame,
viewport_width, viewport_height)` — `// glue:` marker
preserved.
- `examples/inspector_window.rs::paint_inspector(...,
viewport_width, viewport_height)` — both axes plumbed
through.
- `InspectorApp` gains `viewport_height: f32` cached field
refreshed in the `Resized` arm so window-drag responsively
updates the canvas viewport rect.
Stale comment that said "Window height isn't passed through
this signature; assume 600 px" updated to cite the codex
finding.
Verification:
- `cargo build -p openpencil-shell-native --example
inspector_window` — green
- `cargo build -p openpencil-shell-web --target
wasm32-unknown-unknown --features skia --release` — green
- `wasm-bindgen --target web` — produces ../pkg/*
- `bash tools/check-wasm-bundle.sh` — PASS, 0 env.*, 907 092
bytes gzip = 86% of 1 MiB ceiling
- `grep "640.0\|600.0" crates/openpencil-shell-web/src/widget_
host.rs crates/openpencil-shell-native/src/widget_host.rs`
— only one match, inside a comment citing the prior bug
007e97ba03