How does MAUI apply implicit style?

[alexdi220]

Hi, I've researched the way how I can use implicit styles for custom components. Now I guess that it is not the best way because the custom implicit style (placed in the application or local resources) overrides my styles.

But faced one side effect, if I've place style to App.xaml resources it works - implicit styles work like merged. Looked at a code. That is caused by a sequence of calling:

• For an example, I use the Button. First style placed in App.xaml, second - MainPage.xaml
• Button.ctor calls NavigableElement.ctor and register implicit styles. App.xaml resources were loaded at that time and the OnImplicitStyleChanged raised immediately
• The first style apply own setters to bindable the object and place a new value to _originalValues
• OnParentResourcesChanged raise an updated implicit style
• The second style applies. It calls the previous style UnApply which restores properties from Setter._originalValues
• So, the Button has BackgroundColor from the first style and TextColor from the second.

Is that a behavior bug or an expected case? It works in MAUI and Xamarin.Forms for Android. Guess, my description is too hard, so I'm open to discussion.

<Application xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:app1="clr-namespace:App1;assembly=App1"
             x:Class="App1.App">
    <Application.Resources>
        <Style TargetType="Button">
            <Setter Property="TextColor" Value="Green" />
            <Setter Property="BackgroundColor" Value="Red" />
        </Style>
    </Application.Resources>
</Application>

<ContentPage xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             xmlns:local="clr-namespace:App1"
             x:Class="App1.MainPage">
    <ContentPage.Resources>
        <Style TargetType="Button">
            <Setter Property="TextColor" Value="Blue"/>
        </Style>
    </ContentPage.Resources>
			 
    <ScrollView>
        <StackLayout Orientation="Vertical" >
            <Button Text="TestButton"/>
        </StackLayout>
    </ScrollView>

</ContentPage>