Fix Crop→Blur viewport desync after a crop zoom change

[muukii]

Summary

Fixes a regression where, after changing the zoom in Crop mode and switching to Blur (tool/mask) mode, the crop output rendered small and pinned to the top-left. Toggling the Crop/Blur tabs again corrected it; zooming the other way produced the inverse misplacement.

Root cause

makeToolCropDisplayViewport derives the Metal canvas placement from presentation-layer conversions (currentLayerRect(... usesPresentationLayers:)), gated only on toolSurface.isInteractiveZoomGestureActive == false. This was introduced in #309 to make the mask canvas follow the post-release zoom bounce.

The Crop→Blur switch applies the tool viewport once, synchronously, in the same runloop turn that updateToolScrollGeometry just reconfigured the freshly-un-hidden tool scroll view (non-animated setZoomScale, centerContentInViewport, etc.):

setFeatureFocus → applySurfaceMode(syncsToolViewportFromCrop: true) → updateToolScrollGeometry (model set synchronously) → updateToolCropDisplayViewport() (one-shot, no display link).

At that instant no pinch is active, so usesPresentationLayers == true, but Core Animation has not yet committed the new geometry to the presentation layers — they still hold the previous Blur session's geometry. The one-shot samples that stale transform → small + top-left placement, and because no display link runs afterward, the stale frame sticks until the next mode switch (the "switch back and forth fixes it" symptom).

#308 (GPU-resident source / per-generation content bake), originally suspected, is not involved: it never touches CropView.swift, and EditingCanvasContentBake maps the bake back to the original extent, so it changes layer content, never viewport placement.

Fix

Presentation-layer reads are only meaningful while the viewport display link is actively re-sampling an in-flight bounce. Gate them on whether that link is running:

let usesPresentationLayers = toolSurface.viewportRendering.isRunning
  && toolSurface.isInteractiveZoomGestureActive == false

This flips only the link-idle one-shot paths (i.e. the mode switch) back to the model layers, which the synchronous reconfigure already made authoritative. Every display-link-driven path (interactive pinch, post-release bounce, deceleration) is unchanged, so #309's bounce tracking still works.

Scope / notes

• Scoped to the tool path only. makeCropDisplayViewport has the same presentation-read pattern, but the crop path is not a reported repro and its animator-driven rotation computes the viewport inside a UIViewPropertyAnimator block (where presentation reads are intended), so it is intentionally left untouched.
• The tool path's animator case early-returns (the tool surface is hidden in Crop mode), so the gate is safe there.

Test plan

• xcodebuild -scheme BrightroomUI -destination 'platform=iOS Simulator,name=iPhone 17 Pro' builds.
• Verified on device: Crop zoom change → switch to Blur now displays the crop output correctly (no small/top-left misplacement, no need to toggle tabs).
• Editing canvas renders black on the Simulator, so visual confirmation is device-only.

🤖 Generated with Claude Code