Fix pinch-zoom crash when second finger lands in ScrollElement - #1046
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developer-ocansey merged 1 commit intoJul 24, 2026
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The two-finger pinch path nulled singleTouchStart on the second-finger pointerdown, then handleTouchMove dereferenced it via non-null assertions, throwing 'Cannot read properties of null (reading x)'. Keep singleTouchStart as the pinch anchor for the whole gesture instead of nulling it, drop the inaccurate ! assertions, and clear the anchor on touch end. Also guard the non-primary start against a missing primary. Adds a test reproducing the crash sequence.
PaulOskarSoe
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Jul 24, 2026
developer-ocansey
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July 24, 2026 09:32
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Issue Number
GSM-3157 — runtime crash reported via Sentry.
Overview of PR
Fixes a
TypeError: Cannot read properties of null (reading 'x')thrown during two-finger pinch-zoom on touch devices inScrollElement.The gesture state machine was internally inconsistent:
handleTouchStartnulledsingleTouchStarton the second-fingerpointerdown, thenhandleTouchMove's pinch branch dereferenced it via non-null assertions (singleTouchStart!.x) — throwing at runtime.Changes:
singleTouchStartas the pinch anchor for the whole gesture instead of nulling it on the second-fingerpointerdown— so the pinch-move reads a valid coordinate and no frame is dropped.!non-null assertions in the pinch branch.0.30.0-beta.19and add a CHANGELOG entry.Testing:
mainwith the original TypeError and passes with the fix.