Tk Source Code

The completions feature in IDLE relies on a listbox in an overrideredirect toplevel appearing in front of a shell or editor window. Immediately after that toplevel is created (i.e. without calling update), it is temporarily hidden by being moved to +10000+10000 (although I would think there is a better way to hide it, if doing so is still necessary); it is moved into place onscreen only after receiving a <Configure> event.

Something in the TIP 655 implementation ([2e788489230d]) causes drawRect: to never be entered for the toplevel, leaving it blank (having only a default background color from AppKit).

Tcl script exhibiting this issue:

package require Tk
toplevel .t -background green
wm geometry .t +10000+10000
wm overrideredirect .t 1
after 1000 {wm geometry .t +300+300}

Assuming there is only a single display with width w and height h (measured in logical rather than physical pixels), this issue occurs as long as x and y in the early wm geometry +x+y call are not within [-w,w) or [-h,h) respectively. For example, if the display is 1920x1080, then specifying a position above or to the left of -1920-1080 or below or to the right of +1919+1079 will trigger the issue.

I observe this on macOS 12.6.5 Monterey Intel; I have not tried this on other macOS versions.

Also happens on macOS 13.4.1 Ventura Intel.

I notified Python about this issue, and they have removed the wm geometry +10000+10000 call from IDLE: https://github.com/python/cpython/pull/104591

In TkMacOSXMakeRealWindowExist(), doing [window setFrame:geometry display:YES] and then window.styleMask |= NSWindowStyleMaskDocModalWindow seems important to this issue.