vbo: add vbo_always_unmap_buffers()

Drivers can call this function as needed.  It tells the VBO module to
always unmap the current glBegin/glEnd VBO when we flush.  Otherwise
it's possible to be in a flushed state but still have the VBO mapped.

src/mesa/vbo/vbo.h

@@ -127,6 +127,7 @@ vbo_get_minmax_index(struct gl_context *ctx, const struct _mesa_prim *prim,
 
 void vbo_use_buffer_objects(struct gl_context *ctx);
 
+void vbo_always_unmap_buffers(struct gl_context *ctx);
 
 void vbo_set_draw_func(struct gl_context *ctx, vbo_draw_func func);
 

src/mesa/vbo/vbo_exec.h

@@ -143,6 +143,9 @@ struct vbo_exec_context
       const struct gl_client_array *inputs[VERT_ATTRIB_MAX];
    } array;
 
+   /* Which flags to set in vbo_exec_BeginVertices() */
+   GLbitfield begin_vertices_flags;
+
 #ifdef DEBUG
    GLint flush_call_depth;
 #endif

src/mesa/vbo/vbo_exec_api.c

@@ -839,6 +839,19 @@ void vbo_use_buffer_objects(struct gl_context *ctx)
 }
 
 
+/**
+ * If this function is called, all VBO buffers will be unmapped when
+ * we flush.
+ * Otherwise, if a simple command like glColor3f() is called and we flush,
+ * the current VBO may be left mapped.
+ */
+void
+vbo_always_unmap_buffers(struct gl_context *ctx)
+{
+   struct vbo_exec_context *exec = &vbo_context(ctx)->exec;
+   exec->begin_vertices_flags |= FLUSH_STORED_VERTICES;
+}
+
 
 void vbo_exec_vtx_init( struct vbo_exec_context *exec )
 {
@@ -894,6 +907,8 @@ void vbo_exec_vtx_init( struct vbo_exec_context *exec )
    }
 
    exec->vtx.vertex_size = 0;
+
+   exec->begin_vertices_flags = FLUSH_UPDATE_CURRENT;
 }
 
 
@@ -942,7 +957,9 @@ void vbo_exec_BeginVertices( struct gl_context *ctx )
    vbo_exec_vtx_map( exec );
 
    assert((ctx->Driver.NeedFlush & FLUSH_UPDATE_CURRENT) == 0);
-   ctx->Driver.NeedFlush |= FLUSH_UPDATE_CURRENT;
+   assert(exec->begin_vertices_flags);
+
+   ctx->Driver.NeedFlush |= exec->begin_vertices_flags;
 }