[gtk/wip/chergert/macos-iosurface] macos: avoid extra opaque changes

[Christian Hergert <chergert src gnome org>]

commit 81bbf7186ec2b877d1a8ea551a965d7ffda541ea
Author: Christian Hergert <christian hergert me>
Date:   Sun Feb 13 17:09:10 2022 -0800

    macos: avoid extra opaque changes

 gdk/macos/gdkmacosglcontext-private.h | 2 ++
 gdk/macos/gdkmacosglcontext.c         | 8 ++++++--
 2 files changed, 8 insertions(+), 2 deletions(-)
---
diff --git a/gdk/macos/gdkmacosglcontext-private.h b/gdk/macos/gdkmacosglcontext-private.h
index 9d9b378b16..8b3eac2ca6 100644
--- a/gdk/macos/gdkmacosglcontext-private.h
+++ b/gdk/macos/gdkmacosglcontext-private.h
@@ -47,6 +47,8 @@ struct _GdkMacosGLContext
   GLuint texture;
   GLuint target;
   GLuint fbo;
+
+  guint last_opaque : 1;
 };
 
 struct _GdkMacosGLContextClass
diff --git a/gdk/macos/gdkmacosglcontext.c b/gdk/macos/gdkmacosglcontext.c
index 9305188bcd..57e913337c 100644
--- a/gdk/macos/gdkmacosglcontext.c
+++ b/gdk/macos/gdkmacosglcontext.c
@@ -243,8 +243,12 @@ gdk_macos_gl_context_allocate (GdkMacosGLContext *self)
 
   /* Alter to an opaque surface if necessary */
   opaque = _gdk_macos_surface_is_opaque (GDK_MACOS_SURFACE (surface));
-  if (!CHECK (NULL, CGLSetParameter (self->cgl_context, kCGLCPSurfaceOpacity, &opaque)))
-    return;
+  if (opaque != self->last_opaque)
+    {
+      self->last_opaque = !!opaque;
+      if (!CHECK (NULL, CGLSetParameter (self->cgl_context, kCGLCPSurfaceOpacity, &opaque)))
+        return;
+    }
 
   if (self->texture == 0)
     {