Tk Source Code

Most Tk widgets handle <Expose> events by drawing into
a background pixmap and blitting the results to the
screen, for a quick refresh.

The [menu] widget does not; instead it draws directly
to the window.  This leads to a "blinking" effect when
e.g., mousing over menu items or keyboard navigation. 
This is most noticeable on slow displays.

Merged to [0e6c34317cf38621|trunk], core-9-0-branch and core-8-6-branch

Closing

Still the case in 9.1: DisplayMenu() draws the entries directly into the window of the menu, while the other widgets draw into off-screen memory and copy the result in a single operation. 8.6 and 9.0 have the same code.

Fixed on branch x11-menu-double-buffer in [771fe02c90]: every entry is drawn into a pixmap of its size and copied. The rendering is not changed, so there is no test.

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Maybe dealing with 1783474 will make this go away too.

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Reported on the chat that this is apparently still a problem, even on modern hardware (Pentium 4 2.80 GHz and the latest Ubuntu with the Nvidia binary drivers for 3D;  using a nondefault setting for *font seems to exacerbate it:

*font: -*-fixed-*-*-*-*-18-*-*-*-*-*-iso8859-*

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This Tracker item was closed automatically by the system. It was
previously set to a Pending status, and the original submitter
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I should add that I observed this effect on an 25 Mhz SGI Indigo; on modern hardware it's not really noticeable.