BadDataError when trying to rename a window about pyewmh HOT 3 OPEN

This is easily fixed by padding the desired title to the required length:

title += "\0" * (20 - len(title))

Maybe setWmName could be changed to do this automatically:

diff --git a/ewmh/ewmh.py b/ewmh/ewmh.py
index 1302ae6..da149ef 100644
--- a/ewmh/ewmh.py
+++ b/ewmh/ewmh.py
@@ -133,6 +133,7 @@ class EWMH:

                :param win: the window object
                :param name: desired name"""
+               name += '\0' * (20 - len(name))
                self._setProperty('_NET_WM_NAME', name, win)

        def setWmVisibleName(self, win, name):

from pyewmh.

Ok, thanks, there is no error with your fix... But it doesn't rename the window.

I don't really understand why the length title needs to be fixed to 20 chars.

setWmName is not intended to rename windows.

According to pyewmh sources, setWmName() refers to the _NET_WM_NAME proterty, which is, according to the EWMH specs, should rename a window:

The Client SHOULD set this to the title of the window in UTF-8 encoding. If set, the Window Manager should use this in preference to WM_NAME.

from pyewmh.

See X11’s documentation, D.5. The ClientMessage event's format:

char data.b[20] (read/write DATA : MAX 20 byte)
If the data is smaller than 20 byte, all data other than available data must be 0.

Python’s Xlib implementation accordingly sets ClientMessage to use a fixed data size of 20:

class ClientMessage(rq.Event):
# ...
                         rq.FixedPropertyData('data', 20)

from pyewmh.