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Fix IndexOutOfRangeException/Infinite loop in UpdateComponent (Track control) #9934

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Fix IndexOutOfRangeException/Infinite loop in UpdateComponent (Track control) #9934

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1402710
Fix IndexOutOfRangeException on i=0 and i=1; fix infinite loop on i=2
h3xds1nz Oct 11, 2024
089d413
Fix double lookup in GetVisualChild
h3xds1nz Oct 11, 2024
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62 changes: 27 additions & 35 deletions ...icrosoft.DotNet.Wpf/src/PresentationFramework/System/Windows/Controls/Primitives/Track.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -120,42 +120,38 @@ private void UpdateComponent(Control oldValue, Control newValue)
{
if (oldValue != newValue)
{
if (_visualChildren == null)
{
_visualChildren = new Visual[3];
}
const int VisualChildrenCount = 3;
const int VisualChildrenMaxIndex = 2;
_visualChildren ??= new Visual[VisualChildrenCount];

// Notify the visual layer that the old component has been removed
if (oldValue != null)
{
// notify the visual layer that the old component has been removed.
RemoveVisualChild(oldValue);
}

// Remove the old value from our z index list and add new value to end
int i = 0;
while (i < 3)
{
// Array isn't full, break
if (_visualChildren[i] == null)
break;
int itemIndex = 0;
int nullIndex = 0;

// found the old value
if (_visualChildren[i] == oldValue)
{
// Move values down until end of array or a null element
while (i < 2 && _visualChildren[i + 1] != null)
{
_visualChildren[i] = _visualChildren[i + 1];
i++;
}
}
else
{
i++;
}
// Find the Count of the items
while (nullIndex < VisualChildrenCount && _visualChildren[nullIndex] != null)
nullIndex++;

// Find the oldValue item index
while (itemIndex < VisualChildrenMaxIndex && _visualChildren[itemIndex] != oldValue)
itemIndex++;

Debug.Assert(_visualChildren[itemIndex] == oldValue, "Attempt to add a 4th item into _visualChildren");

// In case we're replacing a value, we need to shift the items to the left first, and then append newValue as last
nullIndex--;
if (itemIndex < nullIndex)
{
Array.Copy(_visualChildren, itemIndex + 1, _visualChildren, itemIndex, nullIndex - itemIndex);
_visualChildren[nullIndex] = newValue;
}
else // In case there are still leftover NULL items (empty spots) or it is the last one, we just append
{
_visualChildren[itemIndex] = newValue;
}
// Add newValue at end of z-order
_visualChildren[i] = newValue;

AddVisualChild(newValue);

Expand Down Expand Up @@ -375,11 +371,7 @@ public bool IsDirectionReversed
/// </summary>
protected override Visual GetVisualChild(int index)
{
if (_visualChildren == null || _visualChildren[index] == null)
{
throw new ArgumentOutOfRangeException("index", index, SR.Visual_ArgumentOutOfRange);
}
return _visualChildren[index];
return _visualChildren?[index] ?? throw new ArgumentOutOfRangeException(nameof(index), index, SR.Visual_ArgumentOutOfRange);
}

/// <summary>
Expand Down