mesa: Follow ARB_map_buffer_range more stricly.

Namelly, FlushMappedBufferRange takes a subrange relative to the original
range.

1 files changed, 9 insertions, 6 deletions

diff --git a/src/mesa/vbo/vbo_exec_draw.c b/src/mesa/vbo/vbo_exec_draw.c
index 6f8d1f8eb07..b3787459169 100644
--- a/src/mesa/vbo/vbo_exec_draw.c
+++ b/src/mesa/vbo/vbo_exec_draw.c
@@ -240,13 +240,16 @@ static void vbo_exec_vtx_unmap( struct vbo_exec_context *exec )
 
    if (exec->vtx.bufferobj->Name) {
       GLcontext *ctx = exec->ctx;
-      GLintptr offset = exec->vtx.buffer_used;
-      GLsizeiptr length = (exec->vtx.buffer_ptr - exec->vtx.buffer_map) * sizeof(float);
       
-      if(ctx->Driver.FlushMappedBufferRange)
-         ctx->Driver.FlushMappedBufferRange(ctx, target,
-                                            offset, length,
-                                            exec->vtx.bufferobj);
+      if(ctx->Driver.FlushMappedBufferRange) {
+         GLintptr offset = exec->vtx.buffer_used - exec->vtx.bufferobj->Offset;
+         GLsizeiptr length = (exec->vtx.buffer_ptr - exec->vtx.buffer_map) * sizeof(float);
+
+         if(length)
+            ctx->Driver.FlushMappedBufferRange(ctx, target,
+                                               offset, length,
+                                               exec->vtx.bufferobj);
+      }
 
       exec->vtx.buffer_used += (exec->vtx.buffer_ptr -
                                 exec->vtx.buffer_map) * sizeof(float);