journal: Support per-framebuffer journals

Instead of having a single journal per context, we now have a
CoglJournal object for each CoglFramebuffer. This means we now don't
have to flush the journal when switching/pushing/popping between
different framebuffers so for example a Clutter scene that involves some
ClutterEffect actors that transiently redirect to an FBO can still be
batched.

This also allows us to track state in the journal that relates to the
current frame of its associated framebuffer which we'll need for our
optimization for using the CPU to handle reading a single pixel back
from a framebuffer when we know the whole scene is currently comprised
of simple rectangles in a journal.

cogl/cogl-framebuffer-private.h

@@ -27,6 +27,7 @@
 #include "cogl-handle.h"
 #include "cogl-matrix-stack.h"
 #include "cogl-clip-state.h"
+#include "cogl-journal-private.h"
 
 typedef enum _CoglFramebufferType {
   COGL_FRAMEBUFFER_TYPE_ONSCREEN,
@@ -57,6 +58,15 @@ struct _CoglFramebuffer
   int                 blue_bits;
   int                 green_bits;
   int                 alpha_bits;
+
+  /* We journal the textured rectangles we want to submit to OpenGL so
+   * we have an oppertunity to batch them together into less draw
+   * calls. */
+  CoglJournal        *journal;
+
+  /* The scene of a given framebuffer may depend on images in other
+   * framebuffers... */
+  GList              *deps;
 };
 
 #define COGL_FRAMEBUFFER(X) ((CoglFramebuffer *)(X))
@@ -144,6 +154,19 @@ _cogl_framebuffer_get_modelview_stack (CoglFramebuffer *framebuffer);
 CoglMatrixStack *
 _cogl_framebuffer_get_projection_stack (CoglFramebuffer *framebuffer);
 
+void
+_cogl_framebuffer_add_dependency (CoglFramebuffer *framebuffer,
+                                  CoglFramebuffer *dependency);
+
+void
+_cogl_framebuffer_remove_all_dependencies (CoglFramebuffer *framebuffer);
+
+void
+_cogl_framebuffer_flush_journal (CoglFramebuffer *framebuffer);
+
+void
+_cogl_framebuffer_flush_dependency_journals (CoglFramebuffer *framebuffer);
+
 typedef enum _CoglFramebufferFlushFlags
 {
   /* XXX: When using this, that imples you are going to manually load the