Tk Source Code

On X11, Tk's <KeyRelease> is not working properly. Or perhaps
<KeyPress> and <KeyRelease> are both buggy, I don't know.

For instance with this code :

 bind . <KeyPress> {puts "%# KeyPress %K"}
 bind . <KeyRelease> {puts "%# KeyRelease %K"}

On X11 while I hold down some key, that prints a stream of alternated
KeyPress and KeyRelease lines, but the proper behaviour should be a
unique <KeyRelease> after each <KeyPress> repeated sequence, for each
physical key down/up pair, with the <KeyRelease> sent exactly when
the key is released. There was a similar bug reported for MacOSX some
years ago. It works correctly on Win32.

I noticed this odd behavior on several Linux X11 desktops, also on X11
on NetBSD, they all have the same issue (always under Tk 8.6.12).

****************

I found this bug while playing around with Tk's classic buttons, where
I also discovered *another* bug regarding spacebar keypress (the
button looks "stuck" after a while of depressing the spacebar). Some
comments here:

 https://groups.google.com/g/comp.lang.tcl/c/nf2mgqaul1E

Many thanks, Serhiy! Merged to main, core-9-0-branch, and core-8-6-branch by commits [cd8ac5d1], [5d9e65a9], and [84526332]. Closing the ticket.

Reproduced: the X server sends a KeyRelease/KeyPress pair for each auto-repeat unless the client enables detectable auto-repeat, which Tk did not do. Fix in branch [6d0c31fd56]: XkbSetDetectableAutoRepeat() is called when the display is opened, so a held key generates repeated KeyPress events and a single KeyRelease, as on Windows and macOS.