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Fix preserving layout(std140) directives with -sGL_EXPLICIT_UNIFORM_BINDING #25839

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Merged
juj merged 2 commits into from
Nov 20, 2025
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Fix preserving layout(std140) directives with -sGL_EXPLICIT_UNIFORM_BINDING #25839

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609ab5c
Fix preserving layout(std140) directives in WebGL shaders when using …
juj Nov 20, 2025
fbbd974
Simplify regex
juj Nov 20, 2025
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4 changes: 2 additions & 2 deletions src/lib/libwebgl.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3273,9 +3273,9 @@ for (/**@suppress{duplicate}*/var i = 0; i <= {{{ GL_POOL_TEMP_BUFFERS_SIZE }}};
// Remove all the layout(binding = x) directives so that they do not make
// their way to the actual WebGL shader compiler. These regexes get quite
// hairy, check against https://regex101.com/ when working on these.
source = source.replace(/layout\s*\(.*?binding\s*=\s*([-\d]+).*?\)/g, ''); // "layout(binding = 3)" -> ""
source = source.replace(/layout\s*\(\s*binding\s*=\s*([-\d]+)\s*\)/g, ''); // "layout(binding = 3)" -> ""
source = source.replace(/(layout\s*\((.*?)),\s*binding\s*=\s*([-\d]+)\)/g, '$1)'); // "layout(std140, binding = 1)" -> "layout(std140)"
source = source.replace(/layout\s*\(\s*binding\s*=\s*([-\d]+)\s*,(.*?)\)/g, 'layout($2)'); // "layout(binding = 1, std140)" -> "layout(std140)"
source = source.replace(/layout\s*\(\s*binding\s*=\s*([-\d]+)\s*,\s*(.*?)\)/g, 'layout($2)'); // "layout(binding = 1, std140)" -> "layout(std140)"
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@juj juj Nov 20, 2025

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This \s* addition is not part of the fix itself, but just to improve cleanliness of the string replace for the assert() in the test below. Without this, layout(binding = 1, std140) was converted to form layout( std140), so the \s* here swallows the stray space before std140.


#if GL_DEBUG
dbg(`Shader source after removing layout binding directives: ${source}`;
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5 changes: 5 additions & 0 deletions test/browser/webgl2_ubo_layout_binding.c
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Expand Up @@ -83,6 +83,11 @@ int main(int argc, char *argv[])
"out vec4 outColor;\n"
"void main() { outColor = vec4(r, green.g, blue[0].b + blue[1].b, 1.0); }");

// The above shader compilation should preserve the std140 layout part in the uniforms, so
// make sure that did happen. (https://github.com/emscripten-core/emscripten/issues/25828)
assert(strstr(emscripten_webgl_get_shader_source_utf8(ps), "layout(std140) uniform Green"));
assert(strstr(emscripten_webgl_get_shader_source_utf8(ps), "layout(std140) uniform Blue"));

GLuint program = CreateProgram(vs, ps);
glUseProgram(program);

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