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Fix JS runtime exception on WebGL getContextAttributes (#25618) #25619

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merged 1 commit into from
Oct 22, 2025
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Fix JS runtime exception on WebGL getContextAttributes (#25618) #25619

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3 changes: 1 addition & 2 deletions src/lib/libhtml5_webgl.js
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Original file line number Diff line number Diff line change
Expand Up @@ -306,9 +306,8 @@ var LibraryHtml5WebGL = {
if (!a) return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_PARAM }}};
c = GL.contexts[c];
if (!c) return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_TARGET }}};
var t = c.GLctx;
var t = c.GLctx?.getContextAttributes();
if (!t) return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_TARGET }}};
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@juj juj Oct 22, 2025

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How about

var t = c.GLctx?.getContextAttributes();
if (!t) return {{{ cDefs.EMSCRIPTEN_RESULT_INVALID_TARGET }}};

?

Although do note that if the GL context is lost, then all subsequent GL calls will fail as well. So if you have a code path that can somehow recover (if it is an iOS 26.1 internal bug, one might not exist), you will need to call emscripten_is_webgl_context_lost() or register to emscripten_set_webglcontextlost_callback() to be notified of a context loss, to do something else.

I.e. the issue will likely not be isolated to this function, but all subsequent GL operations will fail as well.

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@andvgal andvgal Oct 22, 2025

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First of all, that is a blind fix for a runtime exception. The fact that the context is not usable any more is out of scope.

The refactoring suggestion imposes another minimal ECMAScript version. I am not that familiar with the project and its application, but the code around suggests ES6-level of coding about when WebAssembly got first introduced. Optional chaining is ES2020.

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@juj juj Oct 22, 2025

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Emscripten project uses Babel to transpile to older ES standards. Using ?. is ok here.

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@andvgal andvgal Oct 22, 2025

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OK, then following your advice.

t = t.getContextAttributes();

{{{ makeSetValue('a', C_STRUCTS.EmscriptenWebGLContextAttributes.alpha, 't.alpha', 'i8') }}};
{{{ makeSetValue('a', C_STRUCTS.EmscriptenWebGLContextAttributes.depth, 't.depth', 'i8') }}};
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