framebuffer: Optimize _cogl_framebuffer_flush_state()

Previously the cost of _cogl_framebuffer_state_flush() would always
scale by the total amount of state tracked by CoglFramebuffer even in
cases where we knew up-front that we only wanted to flush a subset of
the state or in cases where we requested to flush the same framebuffer
multiple times with no changes being made to the framebuffer.

We now track a set of state changed flags with each framebuffer and
track the current read/draw buffers as part of the CoglContext so that
we can quickly bail out when asked to flush the same framebuffer
multiple times with no changes.

_cogl_framebuffer_flush_state() now takes a mask of the state that we
want to flush and the implementation has been redesigned so that the
cost of checking what needs to be flushed and flushing those changes
now scales by how much state we actually plan to update.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

1 files changed, 9 insertions, 2 deletions

diff --git a/cogl/cogl-journal.c b/cogl/cogl-journal.c
index ad646758..e04bf1c3 100644
--- a/cogl/cogl-journal.c
+++ b/cogl/cogl-journal.c
@@ -710,6 +710,12 @@ _cogl_journal_flush_clip_stacks_and_entries (CoglJournalEntry *batch_start,
 
   _cogl_clip_stack_flush (batch_start->clip_stack, state->framebuffer);
 
+  /* XXX: Because we are manually flushing clip state here we need to
+   * make sure that the clip state gets updated the next time we flush
+   * framebuffer state by marking the current framebuffer's clip state
+   * as changed. */
+  ctx->current_draw_buffer_changes |= COGL_FRAMEBUFFER_STATE_CLIP;
+
   _cogl_matrix_stack_push (state->modelview_stack);
 
   /* If we have transformed all our quads at log time then we ensure
@@ -1373,8 +1379,9 @@ _cogl_journal_flush (CoglJournal *journal,
      state manually */
   _cogl_framebuffer_flush_state (framebuffer,
                                  framebuffer,
-                                 COGL_FRAMEBUFFER_FLUSH_SKIP_MODELVIEW |
-                                 COGL_FRAMEBUFFER_FLUSH_SKIP_CLIP_STATE);
+                                 COGL_FRAMEBUFFER_STATE_ALL &
+                                 ~(COGL_FRAMEBUFFER_STATE_MODELVIEW |
+                                   COGL_FRAMEBUFFER_STATE_CLIP));
 
   state.journal = journal;