[cogl-vertex-buffer] Allow querying back the number of vertices a buffer represents

This may be convenient e.g. at draw time if you are simply drawing all vertices

clutter/cogl/cogl-vertex-buffer.h

@@ -84,6 +84,15 @@ G_BEGIN_DECLS
 CoglHandle
 cogl_vertex_buffer_new (guint n_vertices);
 
+/**
+ * cogl_vertex_buffer_get_n_vertices:
+ * @handle: A vertex buffer handle
+ *
+ * This returns the number of vertices that @handle represents
+ */
+guint
+cogl_vertex_buffer_get_n_vertices (CoglHandle handle);
+
 /**
  * cogl_vertex_buffer_add:
  * @handle: A vertex buffer handle

clutter/cogl/common/cogl-vertex-buffer.c

@@ -221,6 +221,19 @@ cogl_vertex_buffer_new (guint n_vertices)
   return _cogl_vertex_buffer_handle_new (buffer);
 }
 
+guint
+cogl_vertex_buffer_get_n_vertices (CoglHandle handle)
+{
+  CoglVertexBuffer *buffer;
+
+  if (!cogl_is_vertex_buffer (handle))
+    return 0;
+
+  buffer = _cogl_vertex_buffer_pointer_from_handle (handle);
+
+  return buffer->n_vertices;
+}
+
 /* There are a number of standard OpenGL attributes that we deal with
  * specially. These attributes are all namespaced with a "gl_" prefix
  * so we should catch any typos instead of silently adding a custom

doc/reference/cogl/cogl-sections.txt

@@ -298,6 +298,7 @@ cogl_color_get_alpha_float
 <FILE>cogl-vertex-buffer</FILE>
 <TITLE>Vertex Buffers</TITLE>
 cogl_vertex_buffer_new
+cogl_vertex_buffer_get_n_vertices
 cogl_vertex_buffer_ref
 cogl_vertex_buffer_unref
 cogl_vertex_buffer_add