DOM API Bindings and Blazor support

[marinasundstrom]

This probably falls under runtime but I think it is relevant to the Web framework.

There is a project in the Mono repository for generating bindings to the DOM API through JavaScript interop.
The plan/idea is to generate the C# code bindings from TypeScript. But it seems like the effort is on hold.

See: mono/mono#10775

However: I see an opportunity in combining that effort with Blazor, enabling developers to use these classes directly from Razor. (Just for Blazor Web, of course)

Instead of an ElementReference you could cast a random HTML element into its corresponding class to perform stuff you otherwise would need manually write JavaScript (if there is not a third-party library for that)

We need this functionality in order to build powerful web apps with just C#.

I have not thought about the server-side scenario, but I guess that you could trigger JavaScript in the browser similar to today.

<canvas @ref="myCanvas" height="200" width="200" />

@code 
{
    Canvas myCanvas;
    Canvas2DContext context;

    protected async Task OnAfterRenderAsync(bool firstRender) 
    {
       if(!firstRender) 
       {
            if(context == null) 
            {
                context = await myCanvas.GetContextAsync("2d");
            }
            var image = new Img();
            image.Href = "/foo.png";
            await context.DrawImageAsync(image, 25, 25);
        }
    }
}

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[IvanJosipovic]

@SteveSandersonMS, I'm not sure how this task was categorized as "affected-few". This issue literally affects every single Blazor user. Having these capabilities will avoid us having to use tones of JS wrapper NuGet libraries.

Other languages already have this in the works:
https://rustwasm.github.io/wasm-bindgen/examples/dom.html
https://github.com/golang/go/wiki/WebAssembly#interacting-with-the-dom

[AlbertoPa]

@SteveSandersonMS, I'm not sure how this task was categorized as "affected-few". This issue literally affects every single Blazor user. Having these capabilities will avoid us having to use tones of JS wrapper NuGet libraries.

I agree with this. I think it affects more users that we may think, but some just accepted the idea that they should rely on third-party wrappers or write their own JS. Just my 2 cents.

[SteveSandersonMS]

The reasoning is just that directly mutating the DOM is not a primary part of Blazor's UI rendering model. The vast majority of scenarios are handled more efficiently using .razor syntax which ties in with the diff-based rendering system and works well in all hosting models (WebAssembly, Server, WebView).

I totally understand there are cases where you need to step outside this model, which is what JS interop provides for. Perhaps it would be interesting to use this to start a community project that provides access to the full range of JS APIs via .NET wrappers. In the long run, depending on community feedback, it's something that the ASP.NET team might also look into doing, but it's not part of the roadmap for .NET 6.