gdk: Add GDK_DEBUG=srgb

Disables gdk_surface_set_color_profile() for backends and forces
sRGB.

This does not change any GSK renderers, it just turns off any backends
trying to hand us color profiles.

gdk/gdk.c

@@ -19,7 +19,7 @@
  * Modified by the GTK+ Team and others 1997-2000.  See the AUTHORS
  * file for a list of people on the GTK+ Team.  See the ChangeLog
  * files for a list of changes.  These files are distributed with
- * GTK+ at ftp://ftp.gtk.org/pub/gtk/. 
+ * GTK+ at ftp://ftp.gtk.org/pub/gtk/.
  */
 
 #include "config.h"
@@ -130,6 +130,7 @@ static const GdkDebugKey gdk_debug_keys[] = {
   { "vulkan-validate", GDK_DEBUG_VULKAN_VALIDATE, "Load the Vulkan validation layer" },
   { "default-settings",GDK_DEBUG_DEFAULT_SETTINGS, "Force default values for xsettings", TRUE },
   { "high-depth",      GDK_DEBUG_HIGH_DEPTH, "Use high bit depth rendering if possible", TRUE },
+  { "srgb",            GDK_DEBUG_SRGB, "Force sRRGB rendering and turn off color profiles" },
 };
 
 

gdk/gdkdebug.h

@@ -51,6 +51,7 @@ typedef enum {
   GDK_DEBUG_VULKAN_VALIDATE = 1 << 22,
   GDK_DEBUG_DEFAULT_SETTINGS= 1 << 23,
   GDK_DEBUG_HIGH_DEPTH      = 1 << 24,
+  GDK_DEBUG_SRGB            = 1 << 25,
 } GdkDebugFlags;
 
 extern guint _gdk_debug_flags;

gdk/gdksurface.c

@@ -2088,6 +2088,10 @@ void
 gdk_surface_set_color_profile (GdkSurface      *self,
                                GdkColorProfile *color_profile)
 {
+  /* This way we support unsetting, too */ 
+  if (GDK_DISPLAY_DEBUG_CHECK (self->display, SRGB))
+    color_profile = gdk_color_profile_get_srgb();
+
   if (gdk_color_profile_equal (self->color_profile, color_profile))
     return;