[FEATURE] WebAssembly Support

[mattleibow]

The is the issue to track the main WebAssembly support. Several issues have already been opened on this topic in various parts:

• [FEATURE] Support webassembly using CanvasKit ([FEATURE] Support webassembly using CanvasKit #750)
  This is not how we are planning on supporting SkiaSharp in WASM.
• [QUESTION] SkiaSharp wasm support ([QUESTION] SkiaSharp wasm support #1132)
  This is what we are going to be doing here. (duplicate)
• [FEATURE] Support SkiaSharp as a Blazor Extension ([FEATURE] Support SkiaSharp as a Blazor Extension #1194)
  This is what we are going to be doing here.
• [FEATURE] Add a SkiaApi and SKAbstractManagedStream native abstraction ([FEATURE] Add a SkiaApi and SKAbstractManagedStream native abstraction #876)
  This is not needed anymore.

We already have a running build of the required versions in #986 and have published that to the internal feed as 2.80.0-pr.986.37.

There are a few missing things on that build (see the PR) but we can now start to work on the more general WASM builds.

Some issues that are relevant/related:

• [Wasm] unsafe void* parameters are not marshaled properly mono#19943
• [Wasm] Support for MonoPInvokeCallback mono#19944
• Implement support for pinvoke for wasm target. mono#8007
• [Wasm] Add support for P/Invoke through dynamic linking mono#14259

[RChrisCoble]

Regarding:

[FEATURE] Support SkiaSharp as a Blazor Extension (#1194)
This is what we are going to be doing here.

When it's a Blazor Extension you can utilize the SkiaSharp API on the Client or Server Blazor deployment model. I believe what you are doing here is akin to the forked Uno repo, allowing Skia/SkiaSharp to work properly when running under WASM in a client browser. My specific feature request around making it a Blazor Extension was to also allow the API to run on the server with the rendering happening on the client.

This would most likely mean Skia (and maybe SkiaSharp) would need to be running in the Client Browser, with the SkiaSharp API calls being packaged up and marshaled over the Blazor SignalR connection when the Blazor Extension was running on the server.

An example of this was done with the HTML5 Canvas here: https://github.com/BlazorExtensions/Canvas

If you look at that GitHub example, they wrote a wrapper around the HTML5 canvas API's which ended up doing one of the following: (1) If the Blazor Extension was running in a client browser, issued the draw call directly or (2) If the Blazor Extension was running on the server, marshaled the call over the SignalR connection to the client to be executed.

The Blazor server deployment model is valuable in situations where you can't deploy multiple MB's of DLL's down to the client just to draw anything. (with that multiple MB's NOT being Skia/SkiaSharp, but the business logic using the SkiSharp API.)

[hawkerm]

Any updates on this issue? I found this feed https://aka.ms/skiasharp-eap/index.json from another issue, assume that has the same bits called out above?

Is there any sample project in the develop branch that shows how to use the WASM bits yet?

I'm interested in testing out SkiaSharp for a Blazor WebAssembly Client App.

Thanks!

[michaldobrodenka]

Maybe stupid question, I haven't tried it yet - is also HarfBuzz supported on wasm?

[mattleibow]

I think so... I don't think I have a build for that today, but was @Gillibald having a look... Need to check discord again on that one. But I recall that someone managed to get a build of it.

[Gillibald]

Y I could successfully build it for wasm. We had some linker issues that got resolved I guess. We still need the auto generated API bits to run it successfully. We are not far away.

[mattleibow]

Another related issue for getting better WASM support: dotnet/runtime#44636

[nor0x]

Hi @Gillibald 👋
is there an update about HarfBuzz on WebAssembly? I'm working on an UNO application and currently get System.DllNotFoundException: libHarfBuzzSharp

[Gillibald]

The next release of SkiaSharp should contain all the native bits you need. There should be a preview out if I am not mistaken.

[Gillibald]

https://www.nuget.org/packages/HarfBuzzSharp.NativeAssets.WebAssembly/2.6.1.7-preview.40

[nor0x]

nice! thanks for info. I will try the HarfBuzzSharp.NativeAssets.WebAssembly package

[mattleibow]

This has just been merged in #1811