Keep off-screen culling paused while dragging - #321
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The canvas only renders nodes currently inside the viewport. That rule stayed active during drag gestures, so when a drag made the view follow the pointer, any node or connection crossing the viewport edge was removed or inserted mid-gesture - visible popping while things were moving. Measured on a crowded scene: a node and its connection stayed unrendered for over a hundred consecutive frames during a single drag that panned the view. The fix mirrors the existing export-time suspension: a dragActive flag tracks the gesture from its first movement to its release, and off-screen culling is paused while it is set. Culling resumes the moment the drag ends, so the memory and render savings on large scenes are unchanged for everything except the duration of a gesture. Verified with a scripted-drag measurement in headless Chromium: with the fix, zero frames during a boundary-crossing drag had the dragged node or its connection unrendered; connection endpoints stayed within the handle radius (under 8 pixels) of the node on every frame, including with the processor throttled sixfold. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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These three changes were attempts at the drag artifact that were not confirmed to work before shipping, and the most recent one made things worse: with #324 in place the connection lag became visible in the light theme as well, where it had previously been unnoticeable. The most likely cause of that regression is the composition flag. The audit behind #324 established that the flag added in #323 never reached the browser, because the window library passes a conflicting switch and duplicate switches resolve last-one-wins. #324 corrected the delivery, so disabling delegated composition took effect for the first time - and it applies to both themes equally, which matches the report exactly. The stroke width increase and the explicit high-quality smoothing hint in the same change also affect both themes and cannot be ruled out. This restores graphlink_desktop.py, styles.css and gl-vars-dev.css to their state as of #321. The measured performance fixes in #319, #320 and #321 are untouched. Co-authored-by: Claude Opus 5 <noreply@anthropic.com>
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Problem
The canvas saves work by only rendering nodes that are currently inside the visible area. That optimization stayed active during drag gestures. When a drag makes the view follow the pointer, nodes and connections near the edge of the screen cross in and out of the visible area mid-gesture, and the renderer was removing and re-inserting them while everything was moving. On a crowded canvas this showed up as nodes and connections popping in and out during a drag - measured at over a hundred consecutive frames with a node and its connection missing during one drag that panned the view.
Change
A flag now tracks each drag gesture from its first movement to its release, and the only-render-visible optimization is paused while the flag is set - the same suspension mechanism the image-export path already uses. Culling resumes as soon as the drag ends, so the savings on large scenes are unchanged except during the gesture itself.
Test plan