findCanvasEventTarget doesn't use specialHTMLTargets

[JoeOsborn]

Please include the following in your bug report:

Version of emscripten/emsdk:

emcc (Emscripten gcc/clang-like replacement + linker emulating GNU ld) 3.1.71 (4171ae200b77a6c266b0e1ebb507d61d1ade3501)
clang version 20.0.0git (https:/github.com/llvm/llvm-project d6344c1cd0d099f8d99ee320f33fc9254dbe8288)
Target: wasm32-unknown-emscripten
Thread model: posix
InstalledDir: /home/jcoa2018/.local/src/emsdk/upstream/bin

This line in library_html5.js:

emscripten/src/library_html5.js

Line 366 in f0cc3d0

// If that is not found either, query via the regular DOM selector.

Seems like it should fall back to findEventTarget, not manual document querying/ID lookup. At a minimum, it should check specialHTMLTargets[target] as well as the other options.

Right now, if you follow the docs and call your canvas e.g. "!canvas" in specialHTMLTargets, createContext seemingly won't be able to find it.

[sbc100]

It looks like this only effects OFFSCREENCANVAS_SUPPORT right? Otherwise findCanvasEventTarget does map to findEventTarget.

@juj WDYT? I guess that fallback should simply be findEventTarget?

[JoeOsborn]

I like this patch for the return statement of findCanvasEventTargets but an explicit fallback could make sense too:

    // First check out the list of OffscreenCanvases by CSS selector ID ('#myCanvasID')
    return GL.offscreenCanvases[target.substr(1)] // Remove '#' prefix
    // If not found, if one is querying by using DOM tag name selector 'canvas', grab the first
    // OffscreenCanvas that we can find.
    // If that is not found either, query via the regular DOM selector.
     || (target == 'canvas' && Object.keys(GL.offscreenCanvases) && GL.offscreenCanvases[Object.keys(GL.offscreenCanvases)[0]])
     || specialHTMLTargets[target]
#if PTHREADS
     || (typeof document != 'undefined' && document.querySelector(target));
#else
     || document.querySelector(target);
#endif