[cogl/wip/pbo-read-pixels: 11/18] cogl-buffer: Create the buffer store when bound

[Neil Roberts <nroberts src gnome org>]

commit 51c7a7e8494fe904b110697bdf233d69e69244f0
Author: Neil Roberts <neil linux intel com>
Date:   Sat Feb 25 19:14:25 2012 +0000

    cogl-buffer: Create the buffer store when bound
    
    Whenever the buffer is bound with _cogl_buffer_bind Cogl now ensures
    the buffer's data store has been created. Previously it would only
    ensure it was created when it was first mapped or when the first data
    was set on it. This is necessary if we are going to use CoglBuffers
    for retrieving data from GL. In that case the buffer won't be mapped
    or have data set on it before it is used.

 cogl/cogl-buffer.c |  107 ++++++++++++++++++++++++++++-----------------------
 1 files changed, 59 insertions(+), 48 deletions(-)
---
diff --git a/cogl/cogl-buffer.c b/cogl/cogl-buffer.c
index 6825401..23cd15a 100644
--- a/cogl/cogl-buffer.c
+++ b/cogl/cogl-buffer.c
@@ -118,6 +118,34 @@ convert_bind_target_to_gl_target (CoglBufferBindTarget target)
     }
 }
 
+static void *
+_cogl_buffer_bind_no_create (CoglBuffer *buffer,
+                             CoglBufferBindTarget target)
+{
+  CoglContext *ctx = buffer->context;
+
+  _COGL_RETURN_VAL_IF_FAIL (buffer != NULL, NULL);
+
+  /* Don't allow binding the buffer to multiple targets at the same time */
+  _COGL_RETURN_VAL_IF_FAIL (ctx->current_buffer[buffer->last_target] != buffer,
+                            NULL);
+
+  /* Don't allow nesting binds to the same target */
+  _COGL_RETURN_VAL_IF_FAIL (ctx->current_buffer[target] == NULL, NULL);
+
+  buffer->last_target = target;
+  ctx->current_buffer[target] = buffer;
+
+  if (buffer->flags & COGL_BUFFER_FLAG_BUFFER_OBJECT)
+    {
+      GLenum gl_target = convert_bind_target_to_gl_target (buffer->last_target);
+      GE( ctx, glBindBuffer (gl_target, buffer->gl_handle) );
+      return NULL;
+    }
+  else
+    return buffer->data;
+}
+
 static GLenum
 _cogl_buffer_hints_to_gl_enum (CoglBufferUsageHint  usage_hint,
                                CoglBufferUpdateHint update_hint)
@@ -136,6 +164,25 @@ _cogl_buffer_hints_to_gl_enum (CoglBufferUsageHint  usage_hint,
   return GL_STATIC_DRAW;
 }
 
+static void
+bo_recreate_store (CoglBuffer *buffer)
+{
+  GLenum gl_target;
+  GLenum gl_enum;
+
+  /* This assumes the buffer is already bound */
+
+  gl_target = convert_bind_target_to_gl_target (buffer->last_target);
+  gl_enum = _cogl_buffer_hints_to_gl_enum (buffer->usage_hint,
+                                           buffer->update_hint);
+
+  GE( buffer->context, glBufferData (gl_target,
+                                     buffer->size,
+                                     NULL,
+                                     gl_enum) );
+  buffer->store_created = TRUE;
+}
+
 static void *
 bo_map (CoglBuffer       *buffer,
         CoglBufferAccess  access,
@@ -154,7 +201,7 @@ bo_map (CoglBuffer       *buffer,
     return NULL;
 
   target = buffer->last_target;
-  _cogl_buffer_bind (buffer, target);
+  _cogl_buffer_bind_no_create (buffer, target);
 
   gl_target = convert_bind_target_to_gl_target (target);
 
@@ -162,19 +209,7 @@ bo_map (CoglBuffer       *buffer,
    * lazily allows the user of the CoglBuffer to set a hint before the
    * store is created. */
   if (!buffer->store_created || (hints & COGL_BUFFER_MAP_HINT_DISCARD))
-    {
-      GLenum gl_enum;
-
-      gl_enum = _cogl_buffer_hints_to_gl_enum (buffer->usage_hint,
-                                               buffer->update_hint);
-
-
-      GE( ctx, glBufferData (gl_target,
-                             buffer->size,
-                             NULL,
-                             gl_enum) );
-      buffer->store_created = TRUE;
-    }
+    bo_recreate_store (buffer);
 
   GE_RET( data, ctx, glMapBuffer (gl_target,
                                   _cogl_buffer_access_to_gl_enum (access)) );
@@ -191,7 +226,7 @@ bo_unmap (CoglBuffer *buffer)
 {
   CoglContext *ctx = buffer->context;
 
-  _cogl_buffer_bind (buffer, buffer->last_target);
+  _cogl_buffer_bind_no_create (buffer, buffer->last_target);
 
   GE( ctx, glUnmapBuffer (convert_bind_target_to_gl_target
                           (buffer->last_target)) );
@@ -215,20 +250,6 @@ bo_set_data (CoglBuffer   *buffer,
 
   gl_target = convert_bind_target_to_gl_target (target);
 
-  /* create an empty store if we don't have one yet. creating the store
-   * lazily allows the user of the CoglBuffer to set a hint before the
-   * store is created. */
-  if (!buffer->store_created)
-    {
-      GLenum gl_enum = _cogl_buffer_hints_to_gl_enum (buffer->usage_hint,
-                                                      buffer->update_hint);
-      GE( ctx, glBufferData (gl_target,
-                             buffer->size,
-                             NULL,
-                             gl_enum) );
-      buffer->store_created = TRUE;
-    }
-
   GE( ctx, glBufferSubData (gl_target, offset, size, data) );
 
   _cogl_buffer_unbind (buffer);
@@ -331,28 +352,18 @@ _cogl_buffer_access_to_gl_enum (CoglBufferAccess access)
 void *
 _cogl_buffer_bind (CoglBuffer *buffer, CoglBufferBindTarget target)
 {
-  CoglContext *ctx = buffer->context;
-
-  _COGL_RETURN_VAL_IF_FAIL (buffer != NULL, NULL);
-
-  /* Don't allow binding the buffer to multiple targets at the same time */
-  _COGL_RETURN_VAL_IF_FAIL (ctx->current_buffer[buffer->last_target] != buffer,
-                            NULL);
+  void *ret;
 
-  /* Don't allow nesting binds to the same target */
-  _COGL_RETURN_VAL_IF_FAIL (ctx->current_buffer[target] == NULL, NULL);
+  ret = _cogl_buffer_bind_no_create (buffer, target);
 
-  buffer->last_target = target;
-  ctx->current_buffer[target] = buffer;
+  /* create an empty store if we don't have one yet. creating the store
+   * lazily allows the user of the CoglBuffer to set a hint before the
+   * store is created. */
+  if ((buffer->flags & COGL_BUFFER_FLAG_BUFFER_OBJECT) &&
+      !buffer->store_created)
+    bo_recreate_store (buffer);
 
-  if (buffer->flags & COGL_BUFFER_FLAG_BUFFER_OBJECT)
-    {
-      GLenum gl_target = convert_bind_target_to_gl_target (buffer->last_target);
-      GE( ctx, glBindBuffer (gl_target, buffer->gl_handle) );
-      return NULL;
-    }
-  else
-    return buffer->data;
+  return ret;
 }
 
 void