[gtk/wip/matthiasc/shared-glyph-cache] Do away with all the context switching

[Matthias Clasen <matthiasc src gnome org>]

commit b19450b23d8b08148546885c7d1c2b6a462dcd52
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Jun 4 10:53:31 2019 +0000

    Do away with all the context switching
    
    Turns out we don't need it, after all.

 gsk/gl/gskglglyphcache.c | 50 ++++++++++--------------------------------------
 gsk/gl/gskgliconcache.c  | 43 +++++------------------------------------
 2 files changed, 15 insertions(+), 78 deletions(-)
---
diff --git a/gsk/gl/gskglglyphcache.c b/gsk/gl/gskglglyphcache.c
index 41fb9f4ffb..816db7607e 100644
--- a/gsk/gl/gskglglyphcache.c
+++ b/gsk/gl/gskglglyphcache.c
@@ -73,20 +73,11 @@ gsk_gl_glyph_cache_new (GdkDisplay *display)
   return glyph_cache;
 }
 
-static GdkGLContext *
-get_context (GskGLGlyphCache *cache)
-{
-  return (GdkGLContext *)g_object_get_data (G_OBJECT (cache->display), "shared_data_gl_context");
-}
-
 void
 gsk_gl_glyph_cache_free (GskGLGlyphCache *self)
 {
-  GdkGLContext *context = get_context (self);
   guint i;
 
-  gdk_gl_context_make_current (context);
-
   for (i = 0; i < self->atlases->len; i ++)
     {
       GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
@@ -280,16 +271,9 @@ upload_region_or_else (GskGLGlyphCache *self,
                        guint            texture_id,
                        GskImageRegion  *region)
 {
-  GdkGLContext *previous;
-
-  previous = gdk_gl_context_get_current ();
-  gdk_gl_context_make_current (get_context (self));
-
   glBindTexture (GL_TEXTURE_2D, texture_id);
   glTextureSubImage2D (texture_id, 0, region->x, region->y, region->width, region->height,
                    GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, region->data);
-
-  gdk_gl_context_make_current (previous);
 }
 
 static void
@@ -300,10 +284,9 @@ upload_dirty_glyph (GskGLGlyphCache   *self,
 
   g_assert (atlas->user_data != NULL);
 
-  gdk_gl_context_push_debug_group_printf (get_context (self),
-(driver),
--                                         "Uploading glyph %d", ((Dirty
-Glyph *)atlas->user_data)->key->glyph);
+  gdk_gl_context_push_debug_group_printf (gdk_gl_context_get_current (),
+                                          "Uploading glyph %d",
+                                         ((DirtyGlyph *)atlas->user_data)->key->glyph);
 
   if (render_glyph (atlas, (DirtyGlyph *)atlas->user_data, &region))
     {
@@ -311,7 +294,7 @@ Glyph *)atlas->user_data)->key->glyph);
       g_free (region.data);
     }
 
-  gdk_gl_context_pop_debug_group (get_context (self));
+  gdk_gl_context_pop_debug_group (gdk_gl_context_get_current ());
 
   /* TODO: This could be unnecessary. We can just reuse the allocated
    * DirtyGlyph next time.
@@ -387,20 +370,17 @@ gsk_gl_glyph_cache_lookup (GskGLGlyphCache *cache,
   return value;
 }
 
+/* Not using gdk_gl_driver_create_texture here, since we want
+ * this texture to survive the driver and stay around until
+ * the display gets closed.
+ */
 static guint
 create_shared_texture (GskGLGlyphCache *self,
                        int              width,
                        int              height)
 {
-  GdkGLContext *previous;
-  GdkGLContext *context;
   guint texture_id;
 
-  previous = gdk_gl_context_get_current ();
-  context = get_context (self);
-
-  gdk_gl_context_make_current (context);
-
   glGenTextures (1, &texture_id);
   glBindTexture (GL_TEXTURE_2D, texture_id);
 
@@ -410,15 +390,13 @@ create_shared_texture (GskGLGlyphCache *self,
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
-  if (gdk_gl_context_get_use_es (context))
+  if (gdk_gl_context_get_use_es (gdk_gl_context_get_current ()))
     glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
   else
     glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
 
   glBindTexture (GL_TEXTURE_2D, 0);
 
-  gdk_gl_context_make_current (previous);
-
   return texture_id;
 }
 
@@ -433,7 +411,7 @@ gsk_gl_glyph_cache_get_glyph_texture_id (GskGLGlyphCache        *self,
   if (atlas->texture_id == 0)
     {
       atlas->texture_id = create_shared_texture (self, atlas->width, atlas->height);
-      gdk_gl_context_label_object_printf (get_context (self),
+      gdk_gl_context_label_object_printf (gdk_gl_context_get_current (),
                                           GL_TEXTURE, atlas->texture_id,
                                           "Glyph atlas %d", atlas->texture_id);
     }
@@ -452,7 +430,6 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
   GlyphCacheKey *key;
   GskGLCachedGlyph *value;
   GHashTable *removed = g_hash_table_new (g_direct_hash, g_direct_equal);
-  GdkGLContext *previous = NULL;
   guint dropped = 0;
 
   self->timestamp++;
@@ -482,10 +459,6 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
 
           if (atlas->texture_id != 0)
             {
-              previous = gdk_gl_context_get_current ();
-              if (previous != get_context (self))
-                gdk_gl_context_make_current (get_context (self));
-
               glDeleteTextures (1, &atlas->texture_id);
               atlas->texture_id = 0;
             }
@@ -496,9 +469,6 @@ gsk_gl_glyph_cache_begin_frame (GskGLGlyphCache *self)
        }
     }
 
-  if (previous)
-    gdk_gl_context_make_current (previous);
-
   /* Remove all glyphs whose atlas was removed, and
    * mark old glyphs as unused
    */
diff --git a/gsk/gl/gskgliconcache.c b/gsk/gl/gskgliconcache.c
index 3970d31066..04869d388c 100644
--- a/gsk/gl/gskgliconcache.c
+++ b/gsk/gl/gskgliconcache.c
@@ -1,6 +1,7 @@
 #include "gskgliconcacheprivate.h"
 #include "gskgltextureatlasprivate.h"
 #include "gdk/gdktextureprivate.h"
+#include "gdk/gdkglcontextprivate.h"
 
 #include <epoxy/gl.h>
 
@@ -47,20 +48,11 @@ gsk_gl_icon_cache_new (GdkDisplay *display)
   return self;
 }
 
-static GdkGLContext *
-get_context (GskGLIconCache *cache)
-{
-  return (GdkGLContext *)g_object_get_data (G_OBJECT (cache->display), "shared_data_gl_context");
-}
-
 void
 gsk_gl_icon_cache_free (GskGLIconCache *self)
 {
-  GdkGLContext *context = get_context (self);
   guint i, p;
 
-  gdk_gl_context_make_current (context);
-
   for (i = 0, p = self->atlases->len; i < p; i ++)
     {
       GskGLTextureAtlas *atlas = g_ptr_array_index (self->atlases, i);
@@ -84,7 +76,6 @@ gsk_gl_icon_cache_begin_frame (GskGLIconCache *self)
   GHashTableIter iter;
   GdkTexture *texture;
   IconData *icon_data;
-  GdkGLContext *previous = NULL;
 
   /* Increase frame age of all icons */
   g_hash_table_iter_init (&iter, self->icons);
@@ -123,10 +114,6 @@ gsk_gl_icon_cache_begin_frame (GskGLIconCache *self)
 
           if (atlas->texture_id != 0)
             {
-              previous = gdk_gl_context_get_current ();
-              if (previous != get_context (self))
-                gdk_gl_context_make_current (get_context (self));
-
               glDeleteTextures (1, &atlas->texture_id);
               atlas->texture_id = 0;
             }
@@ -135,9 +122,6 @@ gsk_gl_icon_cache_begin_frame (GskGLIconCache *self)
           i --; /* Check the current index again */
         }
     }
-
-  if (previous)
-    gdk_gl_context_make_current (previous);
 }
 
 /* FIXME: this could probably be done more efficiently */
@@ -175,15 +159,8 @@ create_shared_texture (GskGLIconCache *self,
                        int             width,
                        int             height)
 {
-  GdkGLContext *previous;
-  GdkGLContext *context;
   guint texture_id;
 
-  previous = gdk_gl_context_get_current ();
-  context = get_context (self);
-
-  gdk_gl_context_make_current (context);
-
   glGenTextures (1, &texture_id);
   glBindTexture (GL_TEXTURE_2D, texture_id);
 
@@ -193,15 +170,13 @@ create_shared_texture (GskGLIconCache *self,
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
   glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
-  if (gdk_gl_context_get_use_es (context))
+  if (gdk_gl_context_get_use_es (gdk_gl_context_get_current ()))
     glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
   else
     glTexImage2D (GL_TEXTURE_2D, 0, GL_RGBA8, width, height, 0, GL_BGRA, GL_UNSIGNED_BYTE, NULL);
 
   glBindTexture (GL_TEXTURE_2D, 0);
 
-  gdk_gl_context_make_current (previous);
-
   return texture_id;
 }
 
@@ -210,16 +185,9 @@ upload_region_or_else (GskGLIconCache *self,
                        guint           texture_id,
                        GskImageRegion *region)
 {
-  GdkGLContext *previous;
-
-  previous = gdk_gl_context_get_current ();
-  gdk_gl_context_make_current (get_context (self));
-
   glBindTexture (GL_TEXTURE_2D, texture_id);
   glTextureSubImage2D (texture_id, 0, region->x, region->y, region->width, region->height,
                    GL_BGRA, GL_UNSIGNED_INT_8_8_8_8_REV, region->data);
-
-  gdk_gl_context_make_current (previous);
 }
 
 void
@@ -281,7 +249,7 @@ gsk_gl_icon_cache_lookup_or_add (GskGLIconCache  *self,
         atlas = g_malloc (sizeof (GskGLTextureAtlas));
         gsk_gl_texture_atlas_init (atlas, ATLAS_SIZE, ATLAS_SIZE);
         atlas->texture_id = create_shared_texture (self, atlas->width, atlas->height);
-        gdk_gl_context_label_object_printf (get_context (self),
+        gdk_gl_context_label_object_printf (gdk_gl_context_get_current (),
                                             GL_TEXTURE, atlas->texture_id,
                                             "Icon atlas %d", atlas->texture_id);
 
@@ -314,13 +282,12 @@ gsk_gl_icon_cache_lookup_or_add (GskGLIconCache  *self,
     region.height = theight + 2;
     region.data = cairo_image_surface_get_data (padded_surface);
 
-    gdk_gl_context_push_debug_group_printf (get_context (self),
-(driver),
+    gdk_gl_context_push_debug_group_printf (gdk_gl_context_get_current (),
                                             "Uploading texture");
 
     upload_region_or_else (self, atlas->texture_id, &region);
 
-    gdk_gl_context_pop_debug_group (get_context (self));
+    gdk_gl_context_pop_debug_group (gdk_gl_context_get_current ());
 
     *out_texture_id = atlas->texture_id;
     *out_texture_rect = icon_data->texture_rect;