Fixed bug 3361 - Texture color modulation doesn't work with active NONE blend mode (opengl and opengles)

Simon Hug

The GL_SetBlendMode and GLES_SetBlendMode functions of the opengl and opengles renderers call the glTexEnvf to set the texture env mode to either GL_MODULATE (the default) or GL_REPLACE for the NONE blend mode. Using GL_REPLACE disables color and alpha modulation for textures.

These glTexEnv calls were put in the SetBlendMode function back in 2006 [1], but there the NONE code still used the GL_DECAL mode. The GL_REPLACE mode came in 2008 [2]. I'm a bit confused why that wasn't always GL_MODULATE and a bit surprised nobody reported that yet (unless I missed it). I guess only a few use the gles renderer and the newish shaders mask the issue.

src/render/opengl/SDL_render_gl.c

@@ -1098,21 +1098,17 @@ GL_SetBlendMode(GL_RenderData * data, int blendMode)
     if (blendMode != data->current.blendMode) {
         switch (blendMode) {
         case SDL_BLENDMODE_NONE:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
             data->glDisable(GL_BLEND);
             break;
         case SDL_BLENDMODE_BLEND:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             data->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
             break;
         case SDL_BLENDMODE_ADD:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             data->glBlendFuncSeparate(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
             break;
         case SDL_BLENDMODE_MOD:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             data->glBlendFuncSeparate(GL_ZERO, GL_SRC_COLOR, GL_ZERO, GL_ONE);
             break;

src/render/opengles/SDL_render_gles.c

@@ -734,11 +734,9 @@ GLES_SetBlendMode(GLES_RenderData * data, int blendMode)
     if (blendMode != data->current.blendMode) {
         switch (blendMode) {
         case SDL_BLENDMODE_NONE:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);
             data->glDisable(GL_BLEND);
             break;
         case SDL_BLENDMODE_BLEND:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             if (data->GL_OES_blend_func_separate_supported) {
                 data->glBlendFuncSeparateOES(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA, GL_ONE, GL_ONE_MINUS_SRC_ALPHA);
@@ -747,7 +745,6 @@ GLES_SetBlendMode(GLES_RenderData * data, int blendMode)
             }
             break;
         case SDL_BLENDMODE_ADD:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             if (data->GL_OES_blend_func_separate_supported) {
                 data->glBlendFuncSeparateOES(GL_SRC_ALPHA, GL_ONE, GL_ZERO, GL_ONE);
@@ -756,7 +753,6 @@ GLES_SetBlendMode(GLES_RenderData * data, int blendMode)
             }
             break;
         case SDL_BLENDMODE_MOD:
-            data->glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
             data->glEnable(GL_BLEND);
             if (data->GL_OES_blend_func_separate_supported) {
                 data->glBlendFuncSeparateOES(GL_ZERO, GL_SRC_COLOR, GL_ZERO, GL_ONE);