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fix(AdornerLayer): re-entrancy-safe lease for zOrderMap snapshot pool #5

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Merged
oysteinkrog merged 2 commits into from
May 16, 2026
Merged

fix(AdornerLayer): re-entrancy-safe lease for zOrderMap snapshot pool #5

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18eaca2
fix(AdornerLayer): re-entrancy-safe lease for zOrderMap snapshot pool
May 15, 2026
e89e154
fix(AdornerLayer): guard lease restore with try/finally on layout exc…
May 16, 2026
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132 changes: 85 additions & 47 deletions src/Microsoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Documents/AdornerLayer.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -458,26 +458,47 @@ protected override Size MeasureOverride(Size constraint)
// Snapshot the values directly into a pooled object[] — SortedList.CopyTo(Array)
// would otherwise allocate a fresh DictionaryEntry[] every layout pass
// (~170 MB in the MotionCatalyst take-open profile).
//
// Re-entrancy: Adorner.Measure callouts can re-enter this method on the same
// AdornerLayer (nested layout passes). A naïve shared field would let the inner
// call's CopyTo overwrite the outer's snapshot and its Array.Clear null out
// slots the outer is still iterating. Lease the field into a local for the
// duration of the call; re-entrant calls allocate their own.
IList valueList = _zOrderMap.GetValueList();
int count = valueList.Count;
if (_zOrderValuesSnapshotBuffer == null || _zOrderValuesSnapshotBuffer.Length < count)
_zOrderValuesSnapshotBuffer = new object[Math.Max(count, 8)];
valueList.CopyTo(_zOrderValuesSnapshotBuffer, 0);

for (int i = 0; i < count; i++)
object[] buffer = _zOrderValuesSnapshotBuffer;
_zOrderValuesSnapshotBuffer = null; // lease

if (buffer == null || buffer.Length < count)
buffer = new object[Math.Max(count, 8)];

try
{
ArrayList adornerInfos = (ArrayList)_zOrderValuesSnapshotBuffer[i];
Debug.Assert(adornerInfos != null, "No adorners found for element in AdornerLayer._zOrderMap");
valueList.CopyTo(buffer, 0);

int j = 0;
while (j < adornerInfos.Count)
for (int i = 0; i < count; i++)
{
AdornerInfo adornerInfo = (AdornerInfo)adornerInfos[j++];
adornerInfo.Adorner.Measure(constraint);
ArrayList adornerInfos = (ArrayList)buffer[i];
Debug.Assert(adornerInfos != null, "No adorners found for element in AdornerLayer._zOrderMap");

int j = 0;
while (j < adornerInfos.Count)
{
AdornerInfo adornerInfo = (AdornerInfo)adornerInfos[j++];
adornerInfo.Adorner.Measure(constraint);
}
}
}
finally
{
Array.Clear(buffer, 0, count);

Array.Clear(_zOrderValuesSnapshotBuffer, 0, count);
// Return the buffer to the pool. If a re-entrant call already restored a
// (possibly larger) buffer, keep the larger one.
if (_zOrderValuesSnapshotBuffer == null || _zOrderValuesSnapshotBuffer.Length < buffer.Length)
_zOrderValuesSnapshotBuffer = buffer;
}

// Returning 0,0 prevents an invalidation of Measure for AdornerLayer from unnecessarily dirtying the parent.
return new Size();
Expand All @@ -497,54 +518,70 @@ protected override Size MeasureOverride(Size constraint)
protected override Size ArrangeOverride(Size finalSize)
{
// Not using an enumerator because the list can be modified during the loop when we call out.
// Snapshot the values directly into the same pooled object[] used by MeasureOverride.
// See MeasureOverride for the pooled-buffer rationale and the lease pattern
// that keeps the pool re-entrancy-safe when Arrange callouts nest.
IList valueList = _zOrderMap.GetValueList();
int count = valueList.Count;
if (_zOrderValuesSnapshotBuffer == null || _zOrderValuesSnapshotBuffer.Length < count)
_zOrderValuesSnapshotBuffer = new object[Math.Max(count, 8)];
valueList.CopyTo(_zOrderValuesSnapshotBuffer, 0);

for (int i = 0; i < count; i++)
{
ArrayList adornerInfos = (ArrayList)_zOrderValuesSnapshotBuffer[i];
object[] buffer = _zOrderValuesSnapshotBuffer;
_zOrderValuesSnapshotBuffer = null; // lease

if (buffer == null || buffer.Length < count)
buffer = new object[Math.Max(count, 8)];

Debug.Assert(adornerInfos != null, "No adorners found for element in AdornerLayer._zOrderMap");
try
{
valueList.CopyTo(buffer, 0);

int j = 0;
while (j < adornerInfos.Count)
for (int i = 0; i < count; i++)
{
AdornerInfo adornerInfo = (AdornerInfo)adornerInfos[j++];
ArrayList adornerInfos = (ArrayList)buffer[i];

Debug.Assert(adornerInfos != null, "No adorners found for element in AdornerLayer._zOrderMap");

if (!adornerInfo.Adorner.IsArrangeValid) // optimization
int j = 0;
while (j < adornerInfos.Count)
{
// We're dependent on Arrange to get the rendersize of the adorner, so Arrange before
// doing our transform magic.
adornerInfo.Adorner.Arrange(new Rect(new Point(), adornerInfo.Adorner.DesiredSize));
GeneralTransform proposedTransform = adornerInfo.Adorner.GetDesiredTransform(adornerInfo.GetTransformForArrange());
GeneralTransform adornerTransform = GetProposedTransform(adornerInfo.Adorner, proposedTransform);
AdornerInfo adornerInfo = (AdornerInfo)adornerInfos[j++];

int index = _children.IndexOf(adornerInfo.Adorner);
if (!adornerInfo.Adorner.IsArrangeValid) // optimization
{
// We're dependent on Arrange to get the rendersize of the adorner, so Arrange before
// doing our transform magic.
adornerInfo.Adorner.Arrange(new Rect(new Point(), adornerInfo.Adorner.DesiredSize));
GeneralTransform proposedTransform = adornerInfo.Adorner.GetDesiredTransform(adornerInfo.GetTransformForArrange());
GeneralTransform adornerTransform = GetProposedTransform(adornerInfo.Adorner, proposedTransform);

if (index >= 0)
int index = _children.IndexOf(adornerInfo.Adorner);

if (index >= 0)
{
// Get the matrix transform out, skip all non affine transforms
Transform transform = adornerTransform?.AffineTransform;

((Adorner)(_children[index])).AdornerTransform = transform;
}
}
if (adornerInfo.Adorner.IsClipEnabled)
{
// Get the matrix transform out, skip all non affine transforms
Transform transform = adornerTransform?.AffineTransform;

((Adorner)(_children[index])).AdornerTransform = transform;
adornerInfo.Adorner.AdornerClip = adornerInfo.Clip;
}
else if (adornerInfo.Adorner.AdornerClip != null)
{
adornerInfo.Adorner.AdornerClip = null;
}
}
if (adornerInfo.Adorner.IsClipEnabled)
{
adornerInfo.Adorner.AdornerClip = adornerInfo.Clip;
}
else if (adornerInfo.Adorner.AdornerClip != null)
{
adornerInfo.Adorner.AdornerClip = null;
}
}
}
finally
{
Array.Clear(buffer, 0, count);

Array.Clear(_zOrderValuesSnapshotBuffer, 0, count);
// Return the buffer to the pool. If a re-entrant call already restored a
// (possibly larger) buffer, keep the larger one.
if (_zOrderValuesSnapshotBuffer == null || _zOrderValuesSnapshotBuffer.Length < buffer.Length)
_zOrderValuesSnapshotBuffer = buffer;
}

return finalSize;
}
Expand Down Expand Up @@ -1189,10 +1226,11 @@ private GeneralTransform GetProposedTransform(Adorner adorner, GeneralTransform
private UIElement[] _keysSnapshotBuffer;

// Pooled snapshot buffer for MeasureOverride / ArrangeOverride iteration
// over _zOrderMap.GetValueList(). Avoids the per-pass DictionaryEntry[]
// allocation that SortedList.CopyTo(Array) would otherwise produce.
// Measure and Arrange share the buffer because they never overlap in a
// single layout pass (Measure runs to completion before Arrange begins).
// over _zOrderMap.GetValueList(). Avoids the per-pass DictionaryEntry[]
// allocation that SortedList.CopyTo(Array) would otherwise produce
// (~170 MB during MotionCatalyst take-open). Accessed via the lease pattern
// in each override so nested Adorner.Measure / Arrange callouts that
// re-enter this same AdornerLayer cannot clobber an outer pass's snapshot.
private object[] _zOrderValuesSnapshotBuffer;

// Dirty-bit gate for OnLayoutUpdated. Set on adorner add/remove and on any
Expand Down
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