diff --git a/src/mesa/shader/shader_api.c b/src/mesa/shader/shader_api.c index 940fe2d03ce..5e87bb40585 100644 --- a/src/mesa/shader/shader_api.c +++ b/src/mesa/shader/shader_api.c @@ -1259,6 +1259,54 @@ lookup_uniform_parameter(GLcontext *ctx, GLuint program, GLint location, } +/** + * GLGL uniform arrays and structs require special handling. + * + * The GL_ARB_shader_objects spec says that if you use + * glGetUniformLocation to get the location of an array, you CANNOT + * access other elements of the array by adding an offset to the + * returned location. For example, you must call + * glGetUniformLocation("foo[16]") if you want to set the 16th element + * of the array with glUniform(). + * + * HOWEVER, some other OpenGL drivers allow accessing array elements + * by adding an offset to the returned array location. And some apps + * seem to depend on that behaviour. + * + * Mesa's gl_uniform_list doesn't directly support this since each + * entry in the list describes one uniform variable, not one uniform + * element. We could insert dummy entries in the list for each array + * element after [0] but that causes complications elsewhere. + * + * We solve this problem by encoding two values in the location that's + * returned by glGetUniformLocation(): + * a) index into gl_uniform_list::Uniforms[] for the uniform + * b) an array/field offset (0 for simple types) + * + * These two values are encoded in the high and low halves of a GLint. + * By putting the uniform number in the high part and the offset in the + * low part, we can support the unofficial ability to index into arrays + * by adding offsets to the location value. + */ +static void +merge_location_offset(GLint *location, GLint offset) +{ + *location = (*location << 16) | offset; +} + + +/** + * Seperate the uniform location and parameter offset. See above. + */ +static void +split_location_offset(GLint *location, GLint *offset) +{ + *offset = *location & 0xffff; + *location = *location >> 16; +} + + + /** * Called via ctx->Driver.GetUniformfv(). */ @@ -1268,6 +1316,9 @@ _mesa_get_uniformfv(GLcontext *ctx, GLuint program, GLint location, { struct gl_program *prog; GLint paramPos; + GLint offset; + + split_location_offset(&location, &offset); lookup_uniform_parameter(ctx, program, location, &prog, ¶mPos); @@ -1298,7 +1349,10 @@ _mesa_get_uniformiv(GLcontext *ctx, GLuint program, GLint location, { struct gl_program *prog; GLint paramPos; + GLint offset; + split_location_offset(&location, &offset); + lookup_uniform_parameter(ctx, program, location, &prog, ¶mPos); if (prog) { @@ -1318,31 +1372,6 @@ _mesa_get_uniformiv(GLcontext *ctx, GLuint program, GLint location, } -/** - * The value returned by GetUniformLocation actually encodes two things: - * 1. the index into the prog->Uniforms[] array for the uniform - * 2. an offset in the prog->ParameterValues[] array for specifying array - * elements or structure fields. - * This function merges those two values. - */ -static void -merge_location_offset(GLint *location, GLint offset) -{ - *location = *location | (offset << 16); -} - - -/** - * Seperate the uniform location and parameter offset. See above. - */ -static void -split_location_offset(GLint *location, GLint *offset) -{ - *offset = (*location >> 16); - *location = *location & 0xffff; -} - - /** * Called via ctx->Driver.GetUniformLocation(). *