[gtk+] GtkGLArea: Only re-allocate buffers during paint

[Alexander Larsson <alexl src gnome org>]

commit 08853c7364651390d888b04e159915d9ba77f7ba
Author: Alexander Larsson <alexl redhat com>
Date:   Tue Dec 16 13:25:23 2014 +0100

    GtkGLArea: Only re-allocate buffers during paint
    
    This drops the maybe_allocate_buffers that re-allocates buffers
    at any point. Instead we just set have_buffers to FALSE and have
    the buffers re-created when needed.
    
    This also makes the buffer creation code imdeponent and makes it
    clean up no longer needed buffers in order to handle being called
    multiple times due to the above.
    
    We also ensure we re-allocate the buffers when we're resizing
    and the buffers are already created.

 gtk/gtkglarea.c |   95 ++++++++++++++++++++++++++++++++-----------------------
 1 files changed, 55 insertions(+), 40 deletions(-)
---
diff --git a/gtk/gtkglarea.c b/gtk/gtkglarea.c
index 44f408e..e68dc01 100644
--- a/gtk/gtkglarea.c
+++ b/gtk/gtkglarea.c
@@ -163,7 +163,7 @@ enum {
   LAST_SIGNAL
 };
 
-static void gtk_gl_area_allocate_buffers (GtkGLArea *area, int width, int height);
+static void gtk_gl_area_allocate_buffers (GtkGLArea *area);
 
 static guint area_signals[LAST_SIGNAL] = { 0, };
 
@@ -322,11 +322,10 @@ gtk_gl_area_resize (GtkGLArea *area, int width, int height)
  * Creates all the buffer objects needed for rendering the scene
  */
 static void
-gtk_gl_area_create_buffers (GtkGLArea *area)
+gtk_gl_area_ensure_buffers (GtkGLArea *area)
 {
   GtkGLAreaPrivate *priv = gtk_gl_area_get_instance_private (area);
   GtkWidget *widget = GTK_WIDGET (area);
-  int scale;
 
   gtk_widget_realize (widget);
 
@@ -341,32 +340,64 @@ gtk_gl_area_create_buffers (GtkGLArea *area)
   glGenFramebuffersEXT (1, &priv->frame_buffer);
 
   if (priv->has_alpha)
-    /* For alpha we use textures as that is required for blending to work */
-    glGenTextures (1, &priv->texture);
+    {
+      /* For alpha we use textures as that is required for blending to work */
+      if (priv->texture == 0)
+        glGenTextures (1, &priv->texture);
+
+      /* Delete old render buffer if any */
+      if (priv->render_buffer != 0)
+        {
+          glDeleteRenderbuffersEXT(1, &priv->render_buffer);
+          priv->render_buffer = 0;
+        }
+    }
   else
+    {
     /* For non-alpha we use render buffers so we can blit instead of texture the result */
-    glGenRenderbuffersEXT (1, &priv->render_buffer);
+      if (priv->render_buffer == 0)
+        glGenRenderbuffersEXT (1, &priv->render_buffer);
 
-  if (priv->has_depth_buffer || priv->has_stencil_buffer)
-    glGenRenderbuffersEXT (1, &priv->depth_stencil_buffer);
+      /* Delete old texture if any */
+      if (priv->texture != 0)
+        {
+          glDeleteTextures(1, &priv->texture);
+          priv->texture = 0;
+        }
+    }
 
-  scale = gtk_widget_get_scale_factor (widget);
-  gtk_gl_area_allocate_buffers (area,
-                                gtk_widget_get_allocated_width (widget) * scale,
-                                gtk_widget_get_allocated_height (widget) * scale);
+  if ((priv->has_depth_buffer || priv->has_stencil_buffer))
+    {
+      if (priv->depth_stencil_buffer == 0)
+        glGenRenderbuffersEXT (1, &priv->depth_stencil_buffer);
+    }
+  else if (priv->depth_stencil_buffer != 0)
+    {
+      /* Delete old depth/stencil buffer */
+      glDeleteRenderbuffersEXT (1, &priv->depth_stencil_buffer);
+      priv->depth_stencil_buffer = 0;
+    }
+
+  gtk_gl_area_allocate_buffers (area);
 }
 
 /*
  * Allocates space of the right type and size for all the buffers
  */
 static void
-gtk_gl_area_allocate_buffers (GtkGLArea *area, int width, int height)
+gtk_gl_area_allocate_buffers (GtkGLArea *area)
 {
   GtkGLAreaPrivate *priv = gtk_gl_area_get_instance_private (area);
+  GtkWidget *widget = GTK_WIDGET (area);
+  int scale, width, height;
 
   if (priv->context == NULL)
     return;
 
+  scale = gtk_widget_get_scale_factor (widget);
+  width = gtk_widget_get_allocated_width (widget) * scale;
+  height = gtk_widget_get_allocated_height (widget) * scale;
+
   if (priv->texture)
     {
       glBindTexture (GL_TEXTURE_2D, priv->texture);
@@ -395,23 +426,6 @@ gtk_gl_area_allocate_buffers (GtkGLArea *area, int width, int height)
   priv->needs_render = TRUE;
 }
 
-static void
-gtk_gl_area_maybe_allocate_buffers (GtkGLArea *area)
-{
-  GtkGLAreaPrivate *priv = gtk_gl_area_get_instance_private (area);
-  GtkWidget *widget = GTK_WIDGET (area);
-  int scale;
-
-  if (!priv->have_buffers)
-    return;
-
-  gtk_gl_area_make_current (area);
-  scale = gtk_widget_get_scale_factor (widget);
-  gtk_gl_area_allocate_buffers (area,
-                                gtk_widget_get_allocated_width (widget) * scale,
-                                gtk_widget_get_allocated_height (widget) * scale);
-}
-
 /**
  * gtk_gl_area_attach_buffers:
  * @area: a #GtkGLArea
@@ -434,7 +448,9 @@ gtk_gl_area_attach_buffers (GtkGLArea *area)
   gtk_gl_area_make_current (area);
 
   if (!priv->have_buffers)
-    gtk_gl_area_create_buffers (area);
+    gtk_gl_area_ensure_buffers (area);
+  else if (priv->needs_resize)
+    gtk_gl_area_allocate_buffers (area);
 
   glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, priv->frame_buffer);
 
@@ -464,14 +480,11 @@ gtk_gl_area_delete_buffers (GtkGLArea *area)
   if (priv->context == NULL)
     return;
 
-  if (!priv->have_buffers)
-    return;
-
   priv->have_buffers = FALSE;
 
   if (priv->render_buffer != 0)
     {
-      glDeleteRenderbuffersEXT(1, &priv->render_buffer);
+      glDeleteRenderbuffersEXT (1, &priv->render_buffer);
       priv->render_buffer = 0;
     }
 
@@ -483,8 +496,12 @@ gtk_gl_area_delete_buffers (GtkGLArea *area)
 
   if (priv->depth_stencil_buffer != 0)
     {
-      glDeleteRenderbuffersEXT(1, &priv->depth_stencil_buffer);
+      glDeleteRenderbuffersEXT (1, &priv->depth_stencil_buffer);
+      priv->depth_stencil_buffer = 0;
+    }
 
+  if (priv->frame_buffer != 0)
+    {
       glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
       glDeleteFramebuffersEXT (1, &priv->frame_buffer);
       priv->frame_buffer = 0;
@@ -588,8 +605,6 @@ gtk_gl_area_size_allocate (GtkWidget     *widget,
 
       priv->needs_resize = TRUE;
     }
-
-  gtk_gl_area_maybe_allocate_buffers (area);
 }
 
 static void
@@ -1131,7 +1146,7 @@ gtk_gl_area_set_has_depth_buffer (GtkGLArea *area,
 
       g_object_notify (G_OBJECT (area), "has-depth-buffer");
 
-      gtk_gl_area_maybe_allocate_buffers (area);
+      priv->have_buffers = FALSE;
     }
 }
 
@@ -1182,7 +1197,7 @@ gtk_gl_area_set_has_stencil_buffer (GtkGLArea *area,
 
       g_object_notify (G_OBJECT (area), "has-stencil-buffer");
 
-      gtk_gl_area_maybe_allocate_buffers (area);
+      priv->have_buffers = FALSE;
     }
 }