`placeAtCanvasCenter` in canvas_io.js was using `canvas.canvas.width` /
`.height` to compute the canvas-center coordinates for newly inserted
nodes. Those properties report the WebGL-style backing-store pixel
buffer dimensions, which on a HiDPI display (Retina/Mac, Windows DPI
scaling > 100%) are `devicePixelRatio` × the visible CSS-pixel
dimensions. LiteGraph's pan/zoom math operates in CSS pixels, so
halving the buffer width put the node at devicePixelRatio× the
visible-center distance from the graph origin — well off the right
edge of the viewport.
Symptom on Mac (Retina, devicePixelRatio = 2): clicking a node in
the Kforge Labs sidebar created the node, but it landed roughly off
the right edge of the visible canvas. The minimap showed it
appearing far from the user's current view; the canvas-center was
unaffected. Worse on zoomed-in / panned canvases.
Why it worked on Windows: most Windows desktops run at 100% DPI
(devicePixelRatio = 1), where buffer pixels and CSS pixels are
identical and the original math is correct.
Fix: use `canvas.canvas.clientWidth` / `.clientHeight` (CSS pixel
dimensions). Falls back to `.width` / `.height` if the canvas hasn't
been laid out yet (during early init), preserving the prior behavior
in that edge case.
No other call sites in the codebase use the same backing-store-pixel
pattern (verified via `grep -rn "canvas\.canvas\.width"` in web/).
The bug was localized to this one helper.
Verification
------------
- `node --input-type=module --check` on canvas_io.js — clean.
- Live test on Mac (synced via `scripts/sync_to_dev.py` to a real
ComfyUI install): clicking a sidebar node row now creates the node
near the canvas center across multiple zoom levels and pan offsets.
Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
