LEGACY_GL_EMULATION: duplicate-texture-load regex truncates sample expressions when a texture matrix is active (invalid GLSL for COMBINE shaders) #27946

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1. kripken

   added

   Desktop OpenGL emulation

   on Oct 12, 2026
2. juj commented on Oct 14, 2026

   

   juj

   on Oct 14, 2026

   Collaborator

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   Could a super-simple sentinel comment work here as a fix?

   diff --git a/src/lib/libglemu.js b/src/lib/libglemu.js
   index 3089630e6e..cce2345bf2 100644
   --- a/src/lib/libglemu.js
   +++ b/src/lib/libglemu.js
   @@ -1105,7 +1105,7 @@ var LibraryGLEmulation = {
            if (TEX_MATRIX_UNIFORM_PREFIX != null) {
              texCoordExpr = `(${TEX_MATRIX_UNIFORM_PREFIX}${texUnitID} * ${texCoordExpr})`;
            }
   -        return `${func}(${TEX_UNIT_UNIFORM_PREFIX}${texUnitID}, ${texCoordExpr}.xy)`;
   +        return `${func}(${TEX_UNIT_UNIFORM_PREFIX}${texUnitID}, ${texCoordExpr}.xy)/*endload*/`;
          }
   
          function getTypeFromCombineOp(op) {
   @@ -1314,7 +1314,7 @@ var LibraryGLEmulation = {
            var lines = this.env.genPassLines(passOutputVar, passInputVar, texUnitID).join('\n');
   
            var texLoadLines = '';
   -        var texLoadRegex = /(texture.*?\(.*?\))/g;
   +        var texLoadRegex = /(texture.*?\(.*?\))\/\*endload\*\//g;
            var loadCounter = 0;
            var load;
   
   @@ -1330,7 +1330,7 @@ var LibraryGLEmulation = {
                texLoadLines += texLoadLine + '\n'; // Store the generated texture load statements in a temp string to not confuse regex search in progress.
                lines = lines.split(texLoadExpr).join(texLoadVar);
                // Reset regex search, since we modified the string.
   -            texLoadRegex = /(texture.*\(.*\))/g;
   +            texLoadRegex = /(texture.*?\(.*?\))\/\*endload\*\//g;
              }
            }
            return [texLoadLines + lines];
3. TheTomBritton commented on Oct 23, 2026

   

   TheTomBritton

   on Oct 23, 2026

   Author

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   Yes, the sentinel works. I made a minimal repro: two GL_COMBINE setups that use the texture more than once, one with two loads on a single line and one with INTERPOLATE, drawn with a texture matrix set. Without the change, the generated shader fails to compile (texload0 = texture2D(u_texUnit0, (u_textureMatrix0 * v_texCoord0);). With your diff it compiles and draws the right colours on Chrome/ANGLE Metal and SwiftShader. The leftover /*endload*/ comments after merging are harmless. PR with your diff plus that test: #28061.