Prevent some NoExpose events from being generated

* src/xterm.c (x_scroll_run): Use the rendering extension if
available to avoid NoExpose events.

1 files changed, 18 insertions, 6 deletions

diff --git a/src/xterm.c b/src/xterm.c
index 948afa56808..89ec43b4705 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -6037,12 +6037,24 @@ x_scroll_run (struct window *w, struct run *run)
     }
   else
 #endif  /* USE_CAIRO */
-    XCopyArea (FRAME_X_DISPLAY (f),
-               FRAME_X_DRAWABLE (f), FRAME_X_DRAWABLE (f),
-               f->output_data.x->normal_gc,
-               x, from_y,
-               width, height,
-               x, to_y);
+    {
+#ifdef HAVE_XRENDER
+      /* Avoid useless NoExpose events.  This way, we only get regular
+         exposure events when there is actually something to
+         expose.  */
+      if (FRAME_X_PICTURE (f) != None)
+        XRenderComposite (FRAME_X_DISPLAY (f), PictOpSrc, FRAME_X_PICTURE (f),
+                          None, FRAME_X_PICTURE (f), x, from_y, 0, 0, x, to_y,
+                          width, height);
+      else
+#endif
+        XCopyArea (FRAME_X_DISPLAY (f),
+                   FRAME_X_DRAWABLE (f), FRAME_X_DRAWABLE (f),
+                   f->output_data.x->normal_gc,
+                   x, from_y,
+                   width, height,
+                   x, to_y);
+    }
 
   unblock_input ();
 }