fix(AdornerLayer): remove unsafe _layoutDirty gate + re-entrancy leases

[oysteinkrog]

Summary

Fixes a correctness regression introduced by 82dc1d5a5 (perf: dirty-bit guard around AdornerLayer.UpdateAdorner walk). The _layoutDirty gate in OnLayoutUpdated was an unsafe coarse correctness gate for coordinate-space changes it cannot comprehensively observe. Reverting only that gate (one line) while keeping the bigger empty-AdornerLayer fast path from dfe6bd478 (17x render-scheduling drop when no user adorners are attached).

Also adds re-entrancy leases on _removeList and _keysSnapshotBuffer since UpdateAdorner now runs on every non-empty LayoutUpdated fire — same lease pattern as _zOrderValuesSnapshotBuffer in MeasureOverride/ArrangeOverride.

The bug

_layoutDirty was gated by:

• Add()/Remove()/Update()/SetAdornerZOrder() setting it true
• Per-adorned-element LayoutUpdated handler OnAdornedElementLayoutUpdated

When a ContentPresenter swaps content (DataContext rebind triggers template application), the intermediate visual subtree between an adorned element E and the AdornerLayer parent is rebuilt. E's TransformToAncestor(adornerLayerParent) will return a different matrix. But E itself may not be re-measured/arranged (only its ancestors are), so E.LayoutUpdated does not fire. Meanwhile the layer's own LayoutUpdated does fire. Result:

• ElementMap.Count > 0 (adorner still registered for E)
• _layoutDirty == false (no per-element handler fired)
• → early return, UpdateAdorner skipped
• Adorner renders with stale (pre-swap) transform

For MotionCatalyst this manifested as: opening a take inside the AnalysisView transitioned UI state correctly, but no video frames or data-boxes appeared (stale transforms mapped them off-screen / to wrong position).

What changes

Single file: AdornerLayer.cs.

 internal void OnLayoutUpdated(object sender, EventArgs args)
 {
     if (ElementMap.Count == 0)
     {
-        _layoutDirty = false;
         return;
     }
-
-    if (!_layoutDirty) return;       // ← THE BUG
-    _layoutDirty = false;
+    // Always run on non-empty layer. Element-level LayoutUpdated subscriptions
+    // miss the case where an ancestor (ContentPresenter content swap) changes
+    // the element's transform relative to the AdornerLayer without firing
+    // layout on the adorned element itself.
     UpdateAdorner(null);
 }

UpdateAdorner is wrapped in try/finally with _removeList and _keysSnapshotBuffer leased per-call.

The _layoutDirty field, OnAdornedElementLayoutUpdated, SubscribeToElementLayout, UnsubscribeFromElementLayout, and _subscribedElements are retained but the field is now write-only. A follow-up cleanup PR can remove the dead infrastructure. Keeping it here keeps the diff minimal and reversible.

Perf impact

• Preserved: the empty-layer fast path (commit dfe6bd478) is the dominant win for default windows. 17x render-scheduling drop when no user adorners — unchanged.
• Preserved: the transform/size/clip change checks inside UpdateElementAdorners still suppress redundant Adorner.InvalidateMeasure calls.
• Reverted: the per-pass _layoutDirty short-circuit when a non-empty layer has no apparent reason to re-walk. Steady-state cost = ElementMap walk + TryTransformToAncestorAsMatrix calls per pass, bounded by the typically-small number of adorners.

Multi-model consensus

Model	Stance	Confidence	Verdict
gpt-5.5-pro	against	7/10	"deleting line 676 is the safest minimal correction"; do not bundle 9dce07e92 revert
gemini-3.1-pro-preview	for	9/10	"completely sufficient"; also recommended _removeList lease pattern (incorporated)

3 parallel Opus agents ruled out other candidates from this perf branch:

• BooleanBoxes.FalseBox/TrueBox in DataBindEngine.RequestRun — DispatcherOperation._args is readonly, no identity-based dedup in dispatch path
• _zOrderMap lease (PR fix(AdornerLayer): re-entrancy-safe lease for zOrderMap snapshot pool #5) — provably correct
• SimpleTransform/HasSimpleTransform fast path — every Transform read audited; semantically equivalent
• _keysSnapshotBuffer pool alone — latent but requires custom adorner re-entrancy
• 214 third-party cherry-picks surveyed — 9dce07e92 (UncommonField always-write FalseBox) flagged medium; kept out of this PR

Full investigation notes: investigation/2026-05-16/.

Validation

• Local WPF build (managed-only, VS18 cannot rebuild C++ projects but pre-built ones reused)
• Binary-swap into MotionCatalyst's BUILD/x64_Debug
• User confirmed: take loads inside AnalysisView with all video viewports, Pressure plate, Launch Monitor, Torque/Force charts visible after ContentPresenter content swap
• Auto-publish via build.yml on merge → InitialForce.WPF 10.0.0-if.81 on nuget.org

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