Add a COGL_DEBUG option to disable the fixed function pipeline backend

This adds COGL_DEBUG=disable-fixed to disable the fixed function
pipeline backend. This is needed to test the GLSL shader generation
because otherwise the fixed function backend would always override it.

cogl/cogl-debug-options.h

@@ -122,6 +122,11 @@ OPT (DISABLE_ARBFP,
      "disable-arbfp",
      "Disable arbfp",
      "Disable use of ARB fragment programs")
+OPT (DISABLE_FIXED,
+     "Root Cause",
+     "disable-fixed",
+     "Disable fixed",
+     "Disable use of the fixed function pipeline backend")
 OPT (DISABLE_GLSL,
      "Root Cause",
      "disable-glsl",

cogl/cogl-debug.c

@@ -68,6 +68,7 @@ static const GDebugKey cogl_behavioural_debug_keys[] = {
   { "disable-atlas", COGL_DEBUG_DISABLE_ATLAS },
   { "disable-texturing", COGL_DEBUG_DISABLE_TEXTURING},
   { "disable-arbfp", COGL_DEBUG_DISABLE_ARBFP},
+  { "disable-fixed", COGL_DEBUG_DISABLE_FIXED},
   { "disable-glsl", COGL_DEBUG_DISABLE_GLSL},
   { "disable-blending", COGL_DEBUG_DISABLE_BLENDING},
   { "disable-npot-textures", COGL_DEBUG_DISABLE_NPOT_TEXTURES},

cogl/cogl-debug.h

@@ -51,13 +51,14 @@ typedef enum {
   COGL_DEBUG_OPENGL           = 1 << 18,
   COGL_DEBUG_DISABLE_TEXTURING = 1 << 19,
   COGL_DEBUG_DISABLE_ARBFP    = 1 << 20,
-  COGL_DEBUG_DISABLE_GLSL     = 1 << 21,
-  COGL_DEBUG_SHOW_SOURCE      = 1 << 22,
-  COGL_DEBUG_DISABLE_BLENDING = 1 << 23,
-  COGL_DEBUG_TEXTURE_PIXMAP   = 1 << 24,
-  COGL_DEBUG_BITMAP           = 1 << 25,
-  COGL_DEBUG_DISABLE_NPOT_TEXTURES = 1 << 26,
-  COGL_DEBUG_WIREFRAME        = 1 << 27
+  COGL_DEBUG_DISABLE_FIXED    = 1 << 21,
+  COGL_DEBUG_DISABLE_GLSL     = 1 << 22,
+  COGL_DEBUG_SHOW_SOURCE      = 1 << 23,
+  COGL_DEBUG_DISABLE_BLENDING = 1 << 24,
+  COGL_DEBUG_TEXTURE_PIXMAP   = 1 << 25,
+  COGL_DEBUG_BITMAP           = 1 << 26,
+  COGL_DEBUG_DISABLE_NPOT_TEXTURES = 1 << 27,
+  COGL_DEBUG_WIREFRAME        = 1 << 28
 } CoglDebugFlags;
 
 #ifdef COGL_ENABLE_DEBUG

cogl/cogl-pipeline-fixed.c

@@ -74,6 +74,9 @@ _cogl_pipeline_backend_fixed_start (CoglPipeline *pipeline,
 {
   CoglHandle user_program;
 
+  if (G_UNLIKELY (cogl_debug_flags & COGL_DEBUG_DISABLE_FIXED))
+    return FALSE;
+
   user_program = cogl_pipeline_get_user_program (pipeline);
   if (user_program != COGL_INVALID_HANDLE)
     return FALSE;