Don’t call NSAttributedString with HTML from a background thread #26153

kubaflo · 2024-11-27T12:20:07Z

According to Apple's documentation: https://developer.apple.com/documentation/foundation/nsattributedstring/1524613-initwithdata

Don’t call this method from a background thread if the options dictionary includes the NSDocumentTypeDocumentAttribute attribute with a value of NSHTMLTextDocumentType. If you do, the method tries to synchronize with the main thread, fails, and times out. Calling it from the main thread works, but can still time out if the HTML contains references to external resources. The HTML import mechanism is meant for implementing something like markdown (that is, text styles, colors, and so on), not for general HTML import.

Also, it seems to be a common problem among Apple developers:
https://forums.developer.apple.com/forums/thread/115405

Issues Fixed

Fixes #25946

Before	After
Simulator.Screen.Recording.-.iPhone.16.Pro.-.2024-11-27.at.12.54.42.mp4	Simulator.Screen.Recording.-.iPhone.16.Pro.-.2024-11-27.at.12.52.55.mp4

kubaflo · 2024-11-27T19:58:27Z

I now noticed that the crash happens with CarouselView1 only when swiping between more than 2 items, but in the case of CarouselView2 the app crashes instantly when CarouselView2 has more than 1 item

<CarouselView Grid.Row="1">
    <CarouselView.ItemsSource>
        <x:Array Type="{x:Type x:String}">
            <x:String>Item1</x:String>
            <x:String>Item2</x:String>
        </x:Array>
    </CarouselView.ItemsSource>
    <CarouselView.ItemTemplate>
        <DataTemplate>
            <VerticalStackLayout Background="Red">
                <Label Text="Hello"/>
                <Label Text="{Binding .}"
                        TextType="Html"/>
            </VerticalStackLayout>
        </DataTemplate>
    </CarouselView.ItemTemplate>
</CarouselView>

kubaflo · 2024-11-27T20:04:04Z

Ohh I just bumped into a scaling issue with ListView/CollectionView1 and CollectionView1 after changes in this PR:

For the following code:

<Grid RowDefinitions="*,*">
    <CollectionView>
        <CollectionView.ItemsSource>
            <x:Array Type="{x:Type x:String}">
                <x:String>Item1</x:String>
                <x:String>Item1</x:String>
                <x:String>Item1</x:String>
            </x:Array>
        </CollectionView.ItemsSource>
        <CollectionView.ItemTemplate>
            <DataTemplate>
                <VerticalStackLayout>
                    <Label Text="Hello"/>
                    <Label Text="{Binding .}"
                            TextType="Html"/>
                </VerticalStackLayout>
            </DataTemplate>
        </CollectionView.ItemTemplate>
    </CollectionView>

    <StackLayout Grid.Row="1">
        <BindableLayout.ItemsSource>
            <x:Array Type="{x:Type x:String}">
                <x:String>Item1</x:String>
                <x:String>Item1</x:String>
                <x:String>Item1</x:String>
            </x:Array>
        </BindableLayout.ItemsSource>
        <BindableLayout.ItemTemplate>
            <DataTemplate>
                <VerticalStackLayout>
                    <Label Text="Hello"/>
                    <Label Text="{Binding .}"
                            TextType="Html"/>
                </VerticalStackLayout>
            </DataTemplate>
        </BindableLayout.ItemTemplate>
    </StackLayout>
</Grid>

I have a cell scaling issue

It gets automatically fixed after updating any of the Label's properties
@rmarinho do you maybe have an idea why it happens?

rmarinho

Nop, not from the top of my mind, can we rebase, see if it's still a issue and also add a test case for this ?

kubaflo · 2024-12-10T13:09:03Z

Nop, not from the top of my mind, can we rebase, see if it's still a issue and also add a test case for this ?

I've rebased, but the issue is still there without using MainQueue.DispatchAsync
However, I'm not sure if it is a correct fix, because it still regresses the height of HTML text in listView and cv

rmarinho

Failing tests on iOS not related

src/Core/src/Platform/iOS/LabelExtensions.cs

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src/Core/src/Platform/iOS/LabelExtensions.cs:93

The NSError variable nsError is not checked after the NSAttributedString initialization. Add a check for nsError and handle any errors appropriately.

platformLabel.AttributedText = new NSAttributedString(text, attr, ref nsError);

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src/Core/src/Platform/iOS/LabelExtensions.cs:93

Check and handle nsError after assigning NSAttributedString to ensure any errors are properly managed.

platformLabel.AttributedText = new NSAttributedString(text, attr, ref nsError);

kubaflo · 2024-12-17T19:21:04Z

Item1 Item1 Item1

<StackLayout Grid.Row="1">
    <BindableLayout.ItemsSource>
        <x:Array Type="{x:Type x:String}">
            <x:String>Item1</x:String>
            <x:String>Item1</x:String>
            <x:String>Item1</x:String>
        </x:Array>
    </BindableLayout.ItemsSource>
    <BindableLayout.ItemTemplate>
        <DataTemplate>
            <VerticalStackLayout>
                <Label Text="Hello"/>
                <Label Text="{Binding .}"
                        TextType="Html"/>
            </VerticalStackLayout>
        </DataTemplate>
    </BindableLayout.ItemTemplate>
</StackLayout>

I tested and this is fixed with this PR: #25664 But, I believe @albyrock87 divided it into smaller ones

jfversluis · 2024-12-18T08:40:53Z

/azp run

) * Don’t call NSAttributedString with HTML from a background thread * Added a UITest * Refactor * add more comments and move to Controls --------- Co-authored-by: Matthew Leibowitz <mattleibow@live.com>

@Shalini-Ashokan

For more information about inflight process check https://github.com/dotnet/maui/wiki/Inflight-Branch-Process # .NET MAUI Release Notes - inflight/candidate Branch ## MAUI Product Fixes * [iOS] Fix SwipeView programmatic open when background color is set by @Shalini-Ashokan in #29765 * [iOS] FormattedText with text color causes stack overflow - fix by @kubaflo in #29874 * [iOS] Fix AdaptiveTrigger not working as expected by @jsuarezruiz in #20987 * [iOS] Fix for Flyout title is not broken over multiple lines when you rotate your screen by @BagavathiPerumal in #29171 * [Windows] Fix for Assigning null to the SelectedItem of the CollectionView in the SelectionChanged event does not clear the selection by @SyedAbdulAzeemSF4852 in #29288 * Fix TapCoordinates method in Catalyst by @jsuarezruiz in #29775 * Fixed ItemSpacing on CarouselView resizes items [Android] by @Dhivya-SF4094 in #29796 * Perf : ButtonContentTypeConverter now using InvariantCulture to parse double by @antoine-jonathan in #25393 * ToolbarItem behavior with ImageSource iOS - fix by @kubaflo in #28833 * [Android] Fixed Button Shadow Color Transparency Not Applied Correctly by @NanthiniMahalingam in #29371 * Don't call NSAttributedString with HTML from a background thread by @kubaflo in #26153 * [Windows] Implemented the Resize and Downsize functions in the W2DImage class by @HarishwaranVijayakumar in #29138 * Templated indicator view - improvements by @kubaflo in #25642 * Update Issue25946.xaml by @anandhan-rajagopal in #30025 ## Testing * Fixed Test case failure in PR 26153 - iOS by @kubaflo in #29906 * Fixed Test case failure in PR 25642 - snapshots by @kubaflo in #29881 * [Testing] Feature Matrix UITest Cases for RadioButton by @TamilarasanSF4853 in #29744 * [Testing] Feature Matrix UITest Cases for CollectionView ItemsSource Feature by @LogishaSelvarajSF4525 in #29322 * [Testing] Feature Matrix UITest Cases for Stepper by @nivetha-nagalingam in #29731 * [Testing] Feature Matrix UITest Cases for CheckBox Control by @anandhan-rajagopal in #29739 * Update the comment for the test properties by @mattleibow in #27306 ## Dependency Updates * No changes in this category ## Docs * No changes in this category ## Housekeeping * [create-pull-request] automated change by @github-actions[bot] in #29875 * [create-pull-request] automated change by @github-actions[bot] in #29792 * [create-pull-request] automated change by @github-actions[bot] in #29760 **Full Changelog**: origin/main...origin/inflight/candidate

) * Don’t call NSAttributedString with HTML from a background thread * Added a UITest * Refactor * add more comments and move to Controls --------- Co-authored-by: Matthew Leibowitz <mattleibow@live.com>

…net#26153) * Don’t call NSAttributedString with HTML from a background thread * Added a UITest * Refactor * add more comments and move to Controls --------- Co-authored-by: Matthew Leibowitz <mattleibow@live.com>

…ead (dotnet#26153)" This reverts commit 61ee829.

kubaflo requested a review from a team as a code owner November 27, 2024 12:20

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kubaflo added area-controls-collectionview CollectionView, CarouselView, IndicatorView area-controls-label Label, Span community ✨ Community Contribution and removed community ✨ Community Contribution labels Nov 27, 2024

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kubaflo and others added 2 commits May 30, 2025 23:54

Refactor

3be83a0

add more comments and move to Controls

ded5785

mattleibow removed the area-controls-label Label, Span label May 30, 2025

mattleibow force-pushed the fix-25946 branch from 27e23fe to ded5785 Compare May 30, 2025 21:56

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mattleibow mentioned this pull request May 30, 2025

iOS App crashes on iOS 18 when placing html label in carousel view with > 2 elements #25946

Closed

sheiksyedm mentioned this pull request Jun 10, 2025

[2025/06/16] Candidate - In Flight Branch #29886

Merged

kubaflo mentioned this pull request Jun 10, 2025

[iOS] Device tests - html label #29906

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kubaflo mentioned this pull request Jun 10, 2025

[iOS] HTML Label in a Carousel View causes a NSInternalInconsistencyException when carousel is swiped. #29913

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PureWeen modified the milestones: .NET 9 SR8, .NET 9 SR9 Jun 23, 2025

NanthiniMahalingam added a commit to NanthiniMahalingam/maui that referenced this pull request Jul 1, 2025

Revert "Don’t call NSAttributedString with HTML from a background thr…

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…ead (dotnet#26153)" This reverts commit 61ee829.

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