- vertex_store->buffer =
- (GLfloat *) ctx->Driver.MapBufferRange(ctx, 0,
- vertex_store->bufferobj->Size,
- GL_MAP_WRITE_BIT, /* not used */
- vertex_store->bufferobj);
- assert(vertex_store->buffer);
- return vertex_store->buffer + vertex_store->used;
+ /* Map the remaining free space in the VBO */
+ GLintptr offset = vertex_store->used * sizeof(GLfloat);
+ GLsizeiptr size = vertex_store->bufferobj->Size - offset;
+ fi_type *range = (fi_type *)
+ ctx->Driver.MapBufferRange(ctx, offset, size, access,
+ vertex_store->bufferobj,
+ MAP_INTERNAL);
+ if (range) {
+ /* compute address of start of whole buffer (needed elsewhere) */
+ vertex_store->buffer = range - vertex_store->used;
+ assert(vertex_store->buffer);
+ return range;
+ }
+ else {
+ vertex_store->buffer = NULL;
+ return NULL;
+ }