cogl-journal: Use a pool of vertex arrays

Previously whenever the journal is flushed a new vertex array would be
created to contain the vertices. To avoid the overhead of reallocating
a buffer every time, this patch makes it use a pool of 8 buffers which
are cycled in turn. The buffers are never destroyed but instead the
data is replaced. The journal should only ever be using one buffer at
a time but we cache more than one buffer anyway in case the GL driver
is internally using the buffer in which case mapping the buffer may
cause it to create a new buffer anyway.

1 files changed, 12 insertions, 0 deletions

diff --git a/cogl/cogl-journal-private.h b/cogl/cogl-journal-private.h
index 7212dca4..6eb7a2df 100644
--- a/cogl/cogl-journal-private.h
+++ b/cogl/cogl-journal-private.h
@@ -28,6 +28,8 @@
 #include "cogl-handle.h"
 #include "cogl-clip-stack.h"
 
+#define COGL_JOURNAL_VBO_POOL_SIZE 8
+
 typedef struct _CoglJournal
 {
   CoglObject _parent;
@@ -36,6 +38,16 @@ typedef struct _CoglJournal
   GArray *vertices;
   size_t needed_vbo_len;
 
+  /* A pool of attribute buffers is used so that we can avoid repeatedly
+     reallocating buffers. Only one of these buffers at a time will be
+     used by Cogl but we keep more than one alive anyway in case the
+     GL driver is internally using the buffer and it would have to
+     allocate a new one when we start writing to it */
+  CoglAttributeBuffer *vbo_pool[COGL_JOURNAL_VBO_POOL_SIZE];
+  /* The next vbo to use from the pool. We just cycle through them in
+     order */
+  unsigned int next_vbo_in_pool;
+
   int fast_read_pixel_count;
 
 } CoglJournal;