Keep connection paths correct on every frame of a drag - #329
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Screenshots of the live symptom show the line drawn at the position the node occupied earlier in the gesture, with a gap of hundreds of pixels on a fast drag, closing as soon as movement stops. The distance is far more than one frame's worth of movement, so the geometry is not merely late: something is actively drawing the connection from records that trail the gesture. Writing the path once per pointer event, as the previous change did, is not enough on its own. React Flow re-renders the same edges from its own node records immediately afterwards, and if those records are behind the gesture, that render overwrites the correct path with a stale one. The net result on screen is unchanged, which matches the report that the previous change made no difference. The correct geometry is now the last write before every paint for the whole gesture, not just at the moment each pointer event is handled. An animation-frame loop, alive only while a drag is in progress, redraws the affected connections from the latest corrected positions. Whatever React renders in between can no longer be what the user sees. The loop is torn down when the gesture ends and if the canvas unmounts mid-gesture. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Problem
Screenshots of the live symptom show the connection drawn at the position the node occupied earlier in the gesture - a gap of hundreds of pixels during a fast drag, closing as soon as movement stops. That distance is far more than one frame of movement, so this is not simply a late repaint: something is actively drawing the connection from records that trail the gesture.
Writing the path once per pointer event, as #328 did, is not sufficient on its own. React Flow re-renders those same edges from its own node records immediately afterwards, and if those records are behind the gesture, that render overwrites the correct path with a stale one. The result on screen is unchanged - which matches the report that #328 made no observable difference.
Change
The correct geometry is now the last write before every paint for the duration of the gesture, rather than only at the moment each pointer event is handled. An animation-frame loop, alive only while a drag is in progress, redraws the affected connections from the latest corrected positions. Whatever React renders in between can no longer be what ends up on screen.
The loop is torn down when the gesture ends, and also if the canvas unmounts mid-gesture.
Test plan