Layered font image source

[GalaxiaGuy]

Description of Change

The original FontIconSource spec (#3189) included a layered option. This is an implementation for iOS, Android and macOS. My plan is to add the other platforms, but I wanted confirmation this was still likely to be accepted before continuing.

API Changes

[ContentProperty("Layers")]
public class LayeredFontImageSource : ImageSource
{
	public IList<FontImageSource> Layers { get; set; }
	public Color Color { get; set; }
	public string FontFamily { get; set; }
	public string Glyph { get; set; }
	public double Size { get; set; }
}

-->

None

Platforms Affected

• Core/XAML (all platforms)
• iOS
• macOS

Before/After Screenshots

Testing Procedure

Some layered icons have been added to the Font ImageSource gallery

Open questions

I've repurposed FontImageSourceHandler to handle layered and non-layered to share code easier. This does mean that the non-layered case allocates a List. Would it be better to keep them separate.

I initially thought FontFamily and Size were highly likely to be shared between layers, so adding them made sense. Color seemed less likely, but possible. Glyph seems unlikely, but allowing it to be shared wasn't any harder.

Should LayeredFontImageSource inherit from FontImageSource? It doesn't really make sense conceptually and would imply you could have a layer of layers. On the other hand it would be handy fallback if platforms don't get a proper implementation.

There currently isn't a reliable way to detect whether FontImageSource.Size has been set explicitly, or is the default. So if the user has LayeredFontImageSource.Size set to something other than 30, and then wants to override it with 30, that won't be handled correctly.

I could possibly do UWP.

On the subject of UWP, I'm not sure what LoadIconSourceAsync and LoadIconElementAsync should do.

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)

[GalaxiaGuy]

I've added an implementation for macOS. There is some odd clipping happening (that was also happening before) that I haven't been able to fix.

I've also changed the macOS implementation to support screen scaling.

[GalaxiaGuy]

I've now added Android.

[GalaxiaGuy]

I've had issues getting Forms to compile on Windows, so I'm going to have to leave it at Android, iOS and macOS.

The UWP implementation should be straightforward.

[jfversluis]

Hey there @GalaxiaGuy, thank you so much for all your time and effort on this. It really is appreciated. For whatever reason this was left too long and now we're unable to still add this to Forms. If this is still something you'd love to see in .NET MAUI, please open a spec there so we can discuss and hopefully salvage this code and use it there.

Again, thank you!