gdk: Add GDK_DEBUG=no-vsync

That turns off waiting and freezing in the frame clock and in
surfaces and triggers redraws asap.

gdk/gdk.c

@@ -132,6 +132,7 @@ static const GdkDebugKey gdk_debug_keys[] = {
   { "vulkan-validate", GDK_DEBUG_VULKAN_VALIDATE, "Load the Vulkan validation layer", TRUE },
   { "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 },
+  { "no-vsync",        GDK_DEBUG_NO_VSYNC, "Repaint instantly (uses 100% CPU with animations)", TRUE },
 };
 
 

gdk/gdkdebugprivate.h

@@ -52,6 +52,7 @@ typedef enum {
   GDK_DEBUG_VULKAN_VALIDATE = 1 << 23,
   GDK_DEBUG_DEFAULT_SETTINGS= 1 << 24,
   GDK_DEBUG_HIGH_DEPTH      = 1 << 25,
+  GDK_DEBUG_NO_VSYNC        = 1 << 26,
 } GdkDebugFlags;
 
 extern guint _gdk_debug_flags;

gdk/gdkframeclockidle.c

@@ -280,6 +280,9 @@ gdk_frame_clock_idle_is_frozen (GdkFrameClockIdle *self)
 {
   GdkFrameClockIdlePrivate *priv = self->priv;
 
+  if (GDK_DEBUG_CHECK (NO_VSYNC))
+    return FALSE;
+
   return priv->freeze_count > 0;
 }
 
@@ -317,7 +320,8 @@ maybe_start_idle (GdkFrameClockIdle *self,
     {
       guint min_interval = 0;
 
-      if (priv->min_next_frame_time != 0)
+      if (priv->min_next_frame_time != 0 &&
+          !GDK_DEBUG_CHECK (NO_VSYNC))
         {
           gint64 now = g_get_monotonic_time ();
           gint64 min_interval_us = MAX (priv->min_next_frame_time, now) - now;

gdk/gdksurface.c

@@ -1530,6 +1530,9 @@ gdk_surface_freeze_updates (GdkSurface *surface)
 {
   g_return_if_fail (GDK_IS_SURFACE (surface));
 
+  if (GDK_DEBUG_CHECK (NO_VSYNC))
+    return;
+
   surface->update_freeze_count++;
   if (surface->update_freeze_count == 1)
     _gdk_frame_clock_uninhibit_freeze (surface->frame_clock);
@@ -1562,6 +1565,9 @@ gdk_surface_thaw_updates (GdkSurface *surface)
 {
   g_return_if_fail (GDK_IS_SURFACE (surface));
 
+  if (GDK_DEBUG_CHECK (NO_VSYNC))
+    return;
+
   g_return_if_fail (surface->update_freeze_count > 0);
 
   if (--surface->update_freeze_count == 0)