cogl-framebuffer: Separate the draw and read buffer

The current framebuffer is now internally separated so that there can
be a different draw and read buffer. This is required to use the
GL_EXT_framebuffer_blit extension. The current draw and read buffers
are stored as a pair in a single stack so that pushing the draw and
read buffer is done simultaneously with the new
_cogl_push_framebuffers internal function. Calling
cogl_pop_framebuffer will restore both the draw and read buffer to the
previous state. The public cogl_push_framebuffer function is layered
on top of the new function so that it just pushes the same buffer for
both drawing and reading.

When flushing the framebuffer state, the cogl_framebuffer_flush_state
function now tackes a pointer to both the draw and the read
buffer. Anywhere that was just flushing the state for the current
framebuffer with _cogl_get_framebuffer now needs to call both
_cogl_get_draw_buffer and _cogl_get_read_buffer.

1 files changed, 5 insertions, 3 deletions

diff --git a/cogl/cogl-attribute.c b/cogl/cogl-attribute.c
index 5cb89868..5872aa23 100644
--- a/cogl/cogl-attribute.c
+++ b/cogl/cogl-attribute.c
@@ -480,7 +480,7 @@ enable_gl_state (CoglDrawFlags flags,
                  CoglAttribute **attributes,
                  ValidateLayerState *state)
 {
-  CoglFramebuffer *framebuffer = _cogl_get_framebuffer ();
+  CoglFramebuffer *framebuffer = _cogl_get_draw_buffer ();
   int i;
 #ifdef MAY_HAVE_PROGRAMABLE_GL
   GLuint generic_index = 0;
@@ -1060,7 +1060,7 @@ flush_state (CoglDrawFlags flags,
 {
   if (!(flags & COGL_DRAW_SKIP_JOURNAL_FLUSH))
     {
-      CoglFramebuffer *framebuffer = _cogl_get_framebuffer ();
+      CoglFramebuffer *framebuffer = _cogl_get_draw_buffer ();
       _cogl_journal_flush (framebuffer->journal, framebuffer);
     }
 
@@ -1080,7 +1080,9 @@ flush_state (CoglDrawFlags flags,
    * stack can cause some drawing which would change the array
    * pointers. */
   if (!(flags & COGL_DRAW_SKIP_FRAMEBUFFER_FLUSH))
-    _cogl_framebuffer_flush_state (_cogl_get_framebuffer (), 0);
+    _cogl_framebuffer_flush_state (_cogl_get_draw_buffer (),
+                                   _cogl_get_read_buffer (),
+                                   0);
 }
 
 /* This can be called directly by the CoglJournal to draw attributes