Add GDK_GL env var and GdkGLFlags

This moves the GDK_ALWAYS_USE_GL env var to GDK_GL=always.
It also changes GDK_DEBUG=nogl to GDK_GL=disable, as GDK_DEBUG
is really only about debug loggin.

It also adds some completely new flags:

 software-draw-gl:
   Always use software fallback for drawing gl content to a cairo_t.
   This disables the fastpaths that exist for drawing directly to
   a window and instead reads back the pixels into a cairo image
   surface.

 software-draw-surface:
   Always use software fallback for drawing cairo surfaces onto a
   gl-using window.  This disables e.g. texture-from-pixmap on X11.

 software-draw:
   Enables both the above.

1 files changed, 15 insertions, 1 deletions

diff --git a/gdk/gdk.c b/gdk/gdk.c
index e40cdea1a3..2b44b0faaf 100644
--- a/gdk/gdk.c
+++ b/gdk/gdk.c
@@ -134,6 +134,14 @@ static GMutex gdk_threads_mutex;
 static GCallback gdk_threads_lock = NULL;
 static GCallback gdk_threads_unlock = NULL;
 
+static const GDebugKey gdk_gl_keys[] = {
+  {"disable",               GDK_GL_FLAGS_DISABLE},
+  {"always",                GDK_GL_FLAGS_ALWAYS},
+  {"software-draw",         GDK_GL_FLAGS_SOFTWARE_DRAW_GL | GDK_GL_FLAGS_SOFTWARE_DRAW_SURFACE},
+  {"software-draw-gl",      GDK_GL_FLAGS_SOFTWARE_DRAW_GL},
+  {"software-draw-surface", GDK_GL_FLAGS_SOFTWARE_DRAW_SURFACE},
+};
+
 #ifdef G_ENABLE_DEBUG
 static const GDebugKey gdk_debug_keys[] = {
   {"events",        GDK_DEBUG_EVENTS},
@@ -149,7 +157,6 @@ static const GDebugKey gdk_debug_keys[] = {
   {"eventloop",     GDK_DEBUG_EVENTLOOP},
   {"frames",        GDK_DEBUG_FRAMES},
   {"settings",      GDK_DEBUG_SETTINGS},
-  {"nogl",          GDK_DEBUG_NOGL},
   {"opengl",        GDK_DEBUG_OPENGL},
 };
 
@@ -248,6 +255,7 @@ void
 gdk_pre_parse_libgtk_only (void)
 {
   const char *rendering_mode;
+  const gchar *gl_string;
 
   gdk_initialized = TRUE;
 
@@ -268,6 +276,12 @@ gdk_pre_parse_libgtk_only (void)
   }
 #endif  /* G_ENABLE_DEBUG */
 
+  gl_string = getenv("GDK_GL");
+  if (gl_string != NULL)
+    _gdk_gl_flags = g_parse_debug_string (gl_string,
+                                          (GDebugKey *) gdk_gl_keys,
+                                          G_N_ELEMENTS (gdk_gl_keys));
+
   if (getenv ("GDK_NATIVE_WINDOWS"))
     {
       g_warning ("The GDK_NATIVE_WINDOWS environment variable is not supported in GTK3.\n"