Add new ColorSlider & ColorPreviewer Primitives

[robloo]

What does the pull request do?

Adds two new ColorSlider and ColorPreviewer control primitives (in the Avalonia.Controls.Primitives namespace). These are stand-alone controls not based on WinUI code. This relates to #4179.

These are the second and third major controls towards implementing the ColorPicker and the last primitives.

What is the current behavior?

Only the ColorSpectrum primitive exists so far for implementing a ColorPicker.

What is the updated/expected behavior with this PR?

Two additional primitives for the ColorPicker are added: ColorSlider and ColorPreviewer. These composable primitives allow making a nearly fully-functional color picker.

Video.mp4

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

• Both ColorSlider and ColorPreviewer are brand-new controls and not based on WinUI code. They share some code with an internal implementation and ColorPreviewer is currently in a PR updating the UWP (now Windows) community toolkit: ColorPicker Updates CommunityToolkit/WindowsCommunityToolkit#4502.
• ColorSlider has been heavily updated improving upon past implementations. It is now a fully stand-alone primitive that can render itself and in no way depends on other higher-level controls. (The WinUI ColorPickerSlider cannot be used independently and earlier ColorPickerSlider implementations by myself were not this advanced).
• The checkered background brush code is based on @maxkatz6 port here: https://github.com/maxkatz6/AvaloniaWinUI.ColorPicker/blob/d774fb6e287471145bef0e10173802a9450a4904/src/AvaloniaWinUI.ColorPicker/Styles/ColorPicker.xaml#L36-L47. This allows a nice simplification not possible in UWP/WinUI which don't support tiled brushes like WPF did.
• All color picker primitives (ColorSpectrum, ColorSlider and ColorPreviewer) can be two-way bound together through the HsvColor property which supports a lot of the color picker functionality already.
• The ColorSpectrum now renders to device DPI/pixels instead of the device-independent pixels/DPI of Avalonia itself. This removes banding caused by Skia scaling the spectrum to fit the full rectangle Fill when desktop scaling is greater than 100%. This now introduces two coordinate systems to keep track of internally. These can be converted between using the LayoutScale factor.
  1. The actual bitmap which follows the physical device pixels regardless of scaling.
  2. The standard Avalonia control coordinates
• ToDisplayName was implemented for the English language using a new algorithm and KnownColor enum. The algorithm is not open source so a best-guess was done. This enables the color name tooltips in the spectrum now.

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

None

Obsoletions / Deprecations

None

Fixed issues

Relates to #4179.

[avaloniaui-team]

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[avaloniaui-team]

You can test this PR using the following package version. 0.10.999-cibuild0020132-beta. (feed url: https://nuget.avaloniaui.net/repository/avalonia-all/index.json) [PRBUILDID]

[avaloniaui-team]

You can test this PR using the following package version. 0.10.999-cibuild0020133-beta. (feed url: https://nuget.avaloniaui.net/repository/avalonia-all/index.json) [PRBUILDID]

[avaloniaui-team]

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[avaloniaui-team]

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[robloo]

@maxkatz6 This is also ready for review. I know you all are busy but if this is merged soon I can get started on the final PR for the full color-picker. That should actually not be too difficult compared to what is already done. The final PR can also be lower priority as it isn't blocking anything.

[avaloniaui-team]

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[maxkatz6]

Thanks. ColorSlider is definitely way more useful here comparing with one in WinUI implementation.

[avaloniaui-team]

You can test this PR using the following package version. 0.10.999-cibuild0020195-beta. (feed url: https://nuget.avaloniaui.net/repository/avalonia-all/index.json) [PRBUILDID]