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Fix FatalExecutionEngineError on insert at start of soft-wrapped line in TextBox (#11481) #11641

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Fix FatalExecutionEngineError on insert at start of soft-wrapped line in TextBox (#11481) #11641

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fb1920a
Fix FatalExecutionEngineError on insert at start of soft-wrapped line…
wnvko-msft May 14, 2026
6f5b635
Always clear line visuals in FormatIncrementalLine
wnvko-msft May 14, 2026
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76 changes: 35 additions & 41 deletions src/Microsoft.DotNet.Wpf/src/PresentationFramework/MS/Internal/documents/TextBoxView.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2346,43 +2346,45 @@ private void IncrementalMeasureLinesAfterInsert(double constraintWidth, LineProp
}
}

// Walk back through soft-wrap predecessors (lines without a hard break:
// Length == ContentLength) so the whole wrapped paragraph is re-formatted.
int firstAffectedLineIndex = lineIndex;
if (firstAffectedLineIndex > 0)
{
firstAffectedLineIndex--;
while (firstAffectedLineIndex > 0 &&
_lineMetrics[firstAffectedLineIndex - 1].Length == _lineMetrics[firstAffectedLineIndex - 1].ContentLength)
{
firstAffectedLineIndex--;
}
}

TextBoxLine line = new TextBoxLine(this);
int lineOffset;
int lineOffset = _lineMetrics[firstAffectedLineIndex].Offset;
bool endOfParagraph = false;

// We need to re-format the previous line, because if someone inserted
// a hard break, the first directly affected line might now be shorter
// and mergeable with its predecessor.
if (lineIndex > 0) // we can skip this if line wrap is disabled.
// Re-format each line from firstAffectedLineIndex through lineIndex,
// absorbing any successor lines fully covered by the new line.
int idx = firstAffectedLineIndex;
while (idx <= lineIndex && !endOfParagraph)
{
FormatFirstIncrementalLine(lineIndex - 1, constraintWidth, lineProperties, line, out lineOffset, out endOfParagraph);
}
else
{
lineOffset = _lineMetrics[lineIndex].Offset;
}
FormatIncrementalLine(idx, constraintWidth, lineProperties, line, ref lineOffset, out endOfParagraph);

// Format the line directly affected by the change.
// If endOfParagraph == true, then the line was absorbed into its
// predessor (because its new content is thinner, or because the
// TextWrapping property changed).
if (!endOfParagraph)
{
using (line)
while (idx + 1 < _lineMetrics.Count && lineOffset >= _lineMetrics[idx + 1].EndOffset)
{
line.Format(lineOffset, constraintWidth, constraintWidth, lineProperties, _cache.TextRunCache, _cache.TextFormatter);

_lineMetrics[lineIndex] = new LineRecord(lineOffset, line);

lineOffset += line.Length;
endOfParagraph = line.EndOfParagraph;
_lineMetrics.RemoveAt(idx + 1);
RemoveLineVisualRange(idx + 1, 1);
if (idx + 1 <= lineIndex)
{
lineIndex--;
}
}
ClearLineVisual(lineIndex);
lineIndex++;

idx++;
}

// Recalc the following lines not directly affected as needed.
SyncLineMetrics(range, constraintWidth, lineProperties, line, endOfParagraph, lineIndex, lineOffset);
SyncLineMetrics(range, constraintWidth, lineProperties, line, endOfParagraph, idx, lineOffset);

desiredSize = BruteForceCalculateDesiredSize();
}
Expand Down Expand Up @@ -2429,7 +2431,8 @@ private void IncrementalMeasureLinesAfterDelete(double constraintWidth, LineProp
// and mergeable with its predecessor.
if (lineIndex > 0) // we can skip this if line wrap is disabled.
{
FormatFirstIncrementalLine(lineIndex - 1, constraintWidth, lineProperties, line, out lineOffset, out endOfParagraph);
lineOffset = _lineMetrics[lineIndex - 1].Offset;
FormatIncrementalLine(lineIndex - 1, constraintWidth, lineProperties, line, ref lineOffset, out endOfParagraph);
}
else
{
Expand Down Expand Up @@ -2470,15 +2473,10 @@ private void IncrementalMeasureLinesAfterDelete(double constraintWidth, LineProp
desiredSize = BruteForceCalculateDesiredSize();
}

// Helper for IncrementalMeasureLinesAfterInsert, IncrementalMeasureLinesAfterDelete.
// Formats the line preceding the first directly affected line after a TextContainer change.
// In general this line might grow as content in the following line is absorbed.
private void FormatFirstIncrementalLine(int lineIndex, double constraintWidth, LineProperties lineProperties, TextBoxLine line,
out int lineOffset, out bool endOfParagraph)
// Formats the line at lineIndex, updates metrics, and clears the cached visual.
private void FormatIncrementalLine(int lineIndex, double constraintWidth, LineProperties lineProperties, TextBoxLine line,
ref int lineOffset, out bool endOfParagraph)
{
int originalEndOffset = _lineMetrics[lineIndex].EndOffset;
lineOffset = _lineMetrics[lineIndex].Offset;

using (line)
{
line.Format(lineOffset, constraintWidth, constraintWidth, lineProperties, _cache.TextRunCache, _cache.TextFormatter);
Expand All @@ -2489,11 +2487,7 @@ private void FormatFirstIncrementalLine(int lineIndex, double constraintWidth, L
endOfParagraph = line.EndOfParagraph;
}

// Don't clear the cached Visual unless something changed.
if (originalEndOffset != _lineMetrics[lineIndex].EndOffset)
{
ClearLineVisual(lineIndex);
}
ClearLineVisual(lineIndex);
}

// Helper for IncrementalMeasureLinesAfterInsert, IncrementalMeasureLinesAfterDelete.
Expand Down