[gtk+] GdkGL: Fix and clean up gdk_cairo_draw_from_gl()

[Alexander Larsson <alexl src gnome org>]

commit e4bf60224b190638f6a88af897ef7ecdf817dc0e
Author: Alexander Larsson <alexl redhat com>
Date:   Wed Nov 5 09:52:51 2014 +0100

    GdkGL: Fix and clean up gdk_cairo_draw_from_gl()
    
    This was unnecessarily creating a framebuffer in the texture case,
    and it was not properly setting up a framebuffer with the texture
    as source in the software fallback w/ texture source case.

 gdk/gdkgl.c |   47 +++++++++++++++++++++++++++++++----------------
 1 files changed, 31 insertions(+), 16 deletions(-)
---
diff --git a/gdk/gdkgl.c b/gdk/gdkgl.c
index b24bb5d..eaf1112 100644
--- a/gdk/gdkgl.c
+++ b/gdk/gdkgl.c
@@ -105,25 +105,16 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
 
   gdk_gl_context_make_current (context);
 
-  glGenFramebuffersEXT (1, &framebuffer);
-  glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, framebuffer);
-
   if (source_type == GL_RENDERBUFFER)
     {
-      glGetRenderbufferParameteriv (GL_RENDERBUFFER, GL_RENDERBUFFER_ALPHA_SIZE,  &alpha_size);
-
       glBindRenderbufferEXT (GL_RENDERBUFFER_EXT, source);
-      glFramebufferRenderbufferEXT (GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
-                                    GL_RENDERBUFFER_EXT, source);
-      glBindFramebufferEXT (GL_DRAW_FRAMEBUFFER_EXT, 0);
+      glGetRenderbufferParameteriv (GL_RENDERBUFFER, GL_RENDERBUFFER_ALPHA_SIZE,  &alpha_size);
     }
   else if (source_type == GL_TEXTURE)
     {
       glBindTexture (GL_TEXTURE_2D, source);
 
       glGetTexLevelParameteriv (GL_TEXTURE_2D, 0, GL_TEXTURE_ALPHA_SIZE,  &alpha_size);
-
-      glBindFramebufferEXT (GL_DRAW_FRAMEBUFFER_EXT, 0);
     }
   else
     {
@@ -157,6 +148,14 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
       int window_height;
       int i;
 
+      /* Create a framebuffer with the source renderbuffer and
+         make it the current target for reads */
+      glGenFramebuffersEXT (1, &framebuffer);
+      glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, framebuffer);
+      glFramebufferRenderbufferEXT (GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+                                    GL_RENDERBUFFER_EXT, source);
+      glBindFramebufferEXT (GL_DRAW_FRAMEBUFFER_EXT, 0);
+
       /* Translate to impl coords */
       cairo_region_translate (clip_region, dx, dy);
 
@@ -213,6 +212,9 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
 
       glDisable (GL_SCISSOR_TEST);
 
+      glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
+      glDeleteFramebuffersEXT (1, &framebuffer);
+
 #undef FLIP_Y
 
     }
@@ -351,6 +353,22 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
       cairo_surface_set_device_scale (image, buffer_scale, buffer_scale);
 #endif
 
+      glGenFramebuffersEXT (1, &framebuffer);
+      glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, framebuffer);
+
+      if (source_type == GL_RENDERBUFFER)
+        {
+          /* Create a framebuffer with the source renderbuffer and
+             make it the current target for reads */
+          glFramebufferRenderbufferEXT (GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+                                        GL_RENDERBUFFER_EXT, source);
+        }
+      else
+        {
+          glFramebufferTexture2DEXT (GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT,
+                                     GL_TEXTURE_2D, source, 0);
+        }
+
       glPixelStorei (GL_PACK_ALIGNMENT, 4);
       glPixelStorei (GL_PACK_ROW_LENGTH, cairo_image_surface_get_stride (image) / 4);
 
@@ -359,6 +377,9 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
 
       glPixelStorei (GL_PACK_ROW_LENGTH, 0);
 
+      glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
+      glDeleteFramebuffersEXT (1, &framebuffer);
+
       cairo_surface_mark_dirty (image);
 
       /* Invert due to opengl having different origin */
@@ -372,12 +393,6 @@ gdk_cairo_draw_from_gl (cairo_t              *cr,
       cairo_surface_destroy (image);
     }
 
-  glDrawBuffer (GL_BACK);
-  glReadBuffer(GL_BACK);
-
-  glBindFramebufferEXT (GL_FRAMEBUFFER_EXT, 0);
-  glDeleteFramebuffersEXT (1, &framebuffer);
-
   if (clip_region)
     cairo_region_destroy (clip_region);
 }