cogl: Fallback to set_data when mapping a buffer to fill it

In the journal code and when generating the stroke path the vertices
are generated on the fly and stored in a CoglBuffer using
cogl_buffer_map. However cogl_buffer_map is allowed to fail but it
wasn't checking for a NULL return value. In particular on GLES it will
always fail because glMapBuffer is only provided by an extension. This
adds a new pair of internal functions called
_cogl_buffer_{un,}map_for_fill_or_fallback which wrap
cogl_buffer_map. If the map fails then it will instead return a
pointer into a GByteArray attached to the context. When the buffer is
unmapped the array is copied into the buffer using
cogl_buffer_set_data.

1 files changed, 6 insertions, 0 deletions

diff --git a/cogl/cogl-context.h b/cogl/cogl-context.h
index 1d55923d..31f129fc 100644
--- a/cogl/cogl-context.h
+++ b/cogl/cogl-context.h
@@ -229,6 +229,12 @@ typedef struct
      stencil buffer */
   gboolean          current_clip_stack_uses_stencil;
 
+  /* This is used as a temporary buffer to fill a CoglBuffer when
+     cogl_buffer_map fails and we only want to map to fill it with new
+     data */
+  GByteArray       *buffer_map_fallback_array;
+  gboolean          buffer_map_fallback_in_use;
+
   CoglContextDriver drv;
   CoglContextWinsys winsys;
 } CoglContext;