Control themes

The current styling system isn’t really suitable for defining controls themes:

• we don’t have a way to properly specify the default theme
• we don’t have a way to completely re-style a control and prevent the current theme selectors from leaking to such re-styled control

So we need a switchable group of styles that can be associated with a control like Style is associated with one in WPF and basically act like WPF’s style.

<Button>
    <Button.ControlTheme>
        <ControlTheme BasedOn="{x:StaticResource SomeBaseButtonTheme}">
             <Setter Property="Background" "Value"="Red"/>
             <Style Selector=":pointerover">
               <Setter Property="Background" "Value"="Green"/>
             </Style>
        </ControlTheme>
    </Button.ControlTheme>

</Button>

Such control theme could be switched and manipulated by selectors in our regular CSS-like styles.

A control would announce its default theme by implementing

interface IHaveDefaultControlTheme
{
       Style GetDefaultControlTheme();
}

which would be generated by the XAML compiler based on x:DefaultControlThemeFor in a XAML file in the same assembly:

<ControlTheme x:DefaultControlThemeFor="{x:Type MyControl}">

</ControlTheme>

[sgf]

I suggest adding support for CSS-3 directly. Use various advanced improvements made to CSS styles in the web(sass,less,scss…) .

GTK eventually went that route too. However, I think you should create a new issue for that.

Someone has already raised it, and I have already expressed support in this issue. https://github.com/AvaloniaUI/Avalonia/issues/3686

As for which one is better, the shorter the better, the smaller the number of typing characters, the better, and the smaller space in view of the same function, the better.

<Style Selector="TabControl">
    <Setter Property="Background" Value="#F0F0F0"/>
    <Setter Property="Height" Value="120"/>
</Style>

TabControl{
Background:#F0F0F0;
Height:120;
}

[grokys]

Work was started on this a while ago on https://github.com/AvaloniaUI/Avalonia/commits/feature/2769-control-themes - just needs to be finished off.