[backport core/1.40] fix: cache canvas cursor style to avoid redundant DOM writes#9604
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## Summary Cache `canvas.style.cursor` to avoid redundant DOM writes that dirty Firefox's style tree. ## Changes - **What**: Add `_lastCursor` field to `LGraphCanvas._updateCursorStyle()` — only writes `canvas.style.cursor` when the value changes. Eliminates ~347 redundant style mutations per profiling session. ## Review Focus - The fix is 2 lines (cache field + comparison). The unit test validates the caching pattern without requiring full LGraphCanvas instantiation. - This is one of several contributors to Firefox's cascading style recalculation freeze. Each `canvas.style.cursor` write dirties the style tree, which is flushed during the next paint in the canvas render loop. ## Stack 2 of 4 in Firefox perf fix stack. Depends on #9170. <!-- Fixes #ISSUE_NUMBER --> ┆Issue is synchronized with this [Notion page](https://www.notion.so/PR-9171-fix-cache-canvas-cursor-style-to-avoid-redundant-DOM-writes-3116d73d36508139827fe1d644fa1bd0) by [Unito](https://www.unito.io)
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🎨 Storybook Build Status❌ Build failed! ⏰ Completed at: 03/08/2026, 02:34:46 AM UTC 🔗 Links
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Backport of #9171 to
core/1.40Automatically created by backport workflow.
┆Issue is synchronized with this Notion page by Unito