Aqua: don't process idle tasks before withdrawing a window; this helps prevent a flashing window if the root is immediately withdrawn.

1 files changed, 11 insertions, 1 deletions

diff --git a/macosx/tkMacOSXWm.c b/macosx/tkMacOSXWm.c
index e039072..15cc264 100644
--- a/macosx/tkMacOSXWm.c
+++ b/macosx/tkMacOSXWm.c
@@ -6447,9 +6447,19 @@ TkpWmSetState(
     macWin = TkMacOSXGetNSWindowForDrawable(winPtr->window);
 
     /*
-     * Make sure windows are updated before the state change.
+     * Make sure windows are updated before the state change.  As an exception,
+     * do not process idle tasks before withdrawing a window.  The purpose of
+     * this is to support the common paradigm of immediately withdrawing the
+     * root window.  Processing idle tasks before changing the state causes the
+     * root to briefly flash on the screen, which users of this paradigm find
+     * annoying.  Not processing the events does not guarantee that the window
+     * will not appear but makes it more likely.
      */
 
+    if (state != WithdrawnState) {
+	while (Tcl_DoOneEvent(TCL_IDLE_EVENTS)) {};
+    }
+
     while (Tcl_DoOneEvent(TCL_IDLE_EVENTS)) {};
 
     if (state == WithdrawnState) {