Allow setting custom Animator in property to Setter

[wieslawsoltes]

What does the pull request do?

Allows setting custom Animator in style setter. This allows granular control of animator per property setter in styles useful for implementing custom geometry animators etc.

Example usage:

<Style Selector="Path.animation">
    <Style.Animations>
      <Animation Duration="0:0:1" IterationCount="Infinite">
        <KeyFrame Cue="0%">
          <Setter Property="Data" Value="M150 0 L75 200 L225 200 Z" Animator="{x:Type CustomGeometryAnimator}"/>
        </KeyFrame>
        <KeyFrame Cue="100%">
          <Setter Property="Data" Value="M 100 100 L 300 100 L 200 300 z" Animator="{x:Type CustomGeometryAnimator}"/>
        </KeyFrame>
      </Animation>
    </Style.Animations>
</Style>

<TextBlock HorizontalAlignment="Center" VerticalAlignment="Center">
  <TextBlock.Styles>
    <Style Selector="TextBlock">
      <Style.Animations>
        <Animation Duration="0:0:1" IterationCount="Infinite">
          <KeyFrame Cue="0%">
            <Setter Property="Text" Value="" Animator="{x:Type pages:CustomStringAnimator}"/>
          </KeyFrame>
          <KeyFrame Cue="100%">
            <Setter Property="Text" Value="0123456789" Animator="{x:Type pages:CustomStringAnimator}"/>
          </KeyFrame>
        </Animation>
      </Style.Animations>
    </Style>
  </TextBlock.Styles>
</TextBlock>

What is the current behavior?

You can only register global animators.

What is the updated/expected behavior with this PR?

You can set custom Animator in style setter.

How was the solution implemented (if it's not obvious)?

Added Animator property to Setter class and IAnimationSetter interface.

Checklist

• Added unit tests (if possible)?
• Added XML documentation to any related classes?
• Consider submitting a PR to https://github.com/AvaloniaUI/Documentation with user documentation

Breaking changes

• Animator property has been added to IAnimationSetter interface.
• Animator property has been added to Setter class as required by IAnimationSetter interface contract.

Obsoletions / Deprecations

Fixed issues

[maxkatz6]

Wouldn't this API be confusing outside of animations?
Especially in your example there is no any animations:

<Style Selector="Path">
  <Setter Property="Data" Value="" Animator="{x:Type CustomGeometryAnimator}" />
</Style>

Maybe it's possible to use attached property "Animation.Animator" and explicit "IAnimationSetter.Type Animator" implementation to read value from that attached property?

[wieslawsoltes]

Wouldn't this API be confusing outside of animations?
Especially in your example there is no any animations:

<Style Selector="Path">
  <Setter Property="Data" Value="" Animator="{x:Type CustomGeometryAnimator}" />
</Style>

Maybe it's possible to use attached property "Animation.Animator" and explicit "IAnimationSetter.Type Animator" implementation to read value from that attached property?

That is something I have considered and it would be better api solution, but I was just bit worried about performance of attached properties.

[wieslawsoltes]

Wouldn't this API be confusing outside of animations?
Especially in your example there is no any animations:

<Style Selector="Path">
  <Setter Property="Data" Value="" Animator="{x:Type CustomGeometryAnimator}" />
</Style>

Maybe it's possible to use attached property "Animation.Animator" and explicit "IAnimationSetter.Type Animator" implementation to read value from that attached property?

@maxkatz6 The issue is that Setter is not IAvaloniaObject so we can not set attached property Animation.Animator on setter itself.

[grokys]

Can attached properties work without it being an AvaloniaObject i wonder? IIRC in XAML all you need is a GetX/SetX method for something to be considered an attached property, not sure if the XAML compiler works like that.

[wieslawsoltes]

Can attached properties work without it being an AvaloniaObject i wonder? IIRC in XAML all you need is a GetX/SetX method for something to be considered an attached property, not sure if the XAML compiler works like that.

Seems to be working

https://github.com/wieslawsoltes/Avalonia/tree/feature/SetterAnimatorAttachedPropertyHack

https://github.com/wieslawsoltes/Avalonia/blob/84dd710fc184c322a59f4f8a650d5573f2ba18de/src/Avalonia.Animation/Animation.cs#L197-L211

https://github.com/wieslawsoltes/Avalonia/blob/84dd710fc184c322a59f4f8a650d5573f2ba18de/samples/RenderDemo/Pages/CustomAnimatorPage.xaml#L14

[wieslawsoltes]

Open draft PR with attached property solution #6082

Letting the discussion continue.

[wieslawsoltes]

Better solution without breaking changes in #6082