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Carousel layout cycle renderer bug #9349

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Carousel layout cycle renderer bug #9349

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685e30a
fix for carousel layout cycle renderer bug
Feb 18, 2026
917cdb7
Revert "fix for carousel layout cycle renderer bug"
Feb 18, 2026
84b387b
fixing carousel layout cycle bug
Feb 18, 2026
0f8ce6f
cleanup
Feb 18, 2026
b103d39
nit
Feb 19, 2026
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63 changes: 56 additions & 7 deletions source/uwp/SharedRenderer/lib/AdaptiveCarouselRenderer.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -122,13 +122,51 @@ namespace winrt::AdaptiveCards::Rendering::Xaml_Rendering::implementation
if (carouselPageUI != nullptr)
{
carouselUI.Items().Append(carouselPageUI);
}
}

if (fixedHeightInPixel == 0)
{
carouselPageUI.try_as<FrameworkElement>().LayoutUpdated(
[carouselUI](auto&&, auto&&) { SetFlipViewMaxHeight(carouselUI); });
}
}
// If no fixed height was specified, compute the max height from page content
// after the FlipView has been loaded (not during layout) to avoid layout cycles.
if (fixedHeightInPixel == 0)
{
auto isUpdatingHeight = std::make_shared<bool>(false);

// Use Loaded event to set initial height — fires once after the element
// is in the visual tree and has been measured, but not during a layout pass.
auto loadedToken = carouselUI.Loaded([carouselUI, isUpdatingHeight](auto&&, auto&&) {
if (*isUpdatingHeight)
return;
*isUpdatingHeight = true;
SetFlipViewMaxHeight(carouselUI);
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@godlytalias godlytalias Feb 19, 2026

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SetFlipViewMaxHeight seems to be an operation that figure out the size for flipview by calling Measure operations on the child contents. So ideally this should get called during the Measure operation of FlipView to avoid such cycles.

*isUpdatingHeight = false;
});

// Use SizeChanged to adjust if the FlipView width changes (e.g. window resize).
// SizeChanged fires after layout completes, so it won't cause a layout cycle
// as long as we guard against re-entrancy.
auto sizeChangedToken =
carouselUI.SizeChanged([carouselUI, isUpdatingHeight](auto&&, winrt::SizeChangedEventArgs const&) {
if (*isUpdatingHeight)
return;
*isUpdatingHeight = true;
SetFlipViewMaxHeight(carouselUI);
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@godlytalias godlytalias Feb 19, 2026

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Probably this may cause flickers as this will lead to mismatch of timing where the size change happens for CarouselUI and FlipView

*isUpdatingHeight = false;
});

// Update height when the selected page changes, since pages may differ in size.
auto selectionChangedToken = carouselUI.SelectionChanged([carouselUI, isUpdatingHeight](auto&&, auto&&) {
if (*isUpdatingHeight)
return;
*isUpdatingHeight = true;
SetFlipViewMaxHeight(carouselUI);
*isUpdatingHeight = false;
});

carouselUI.Unloaded([carouselUI, loadedToken, sizeChangedToken, selectionChangedToken](auto&&, auto&&) {
carouselUI.Loaded(loadedToken);
carouselUI.SizeChanged(sizeChangedToken);
carouselUI.SelectionChanged(selectionChangedToken);
});
}

if (carousel.InitialPage())
Expand Down Expand Up @@ -192,11 +230,22 @@ namespace winrt::AdaptiveCards::Rendering::Xaml_Rendering::implementation
void SetFlipViewMaxHeight(FlipView const& flipView)
{
auto selectIndex = flipView.SelectedIndex();

// FIX: Validate selectedIndex is within bounds
if (selectIndex < 0 || static_cast<uint32_t>(selectIndex) >= flipView.Items().Size())
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{
return;
}

auto carouselPageUI = flipView.Items().GetAt(selectIndex).try_as<FrameworkElement>();

if (flipView.IsLoaded())
if (carouselPageUI != nullptr && flipView.IsLoaded())
{
float width = static_cast<float>(flipView.ActualWidth());
if (width <= 0)
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{
return;
}
const winrt::Size noVerticalLimit{width, std::numeric_limits<float>::infinity()};
carouselPageUI.Measure(noVerticalLimit);
auto maxHeight = carouselPageUI.DesiredSize().Height;
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