We actually need to deliver the signal synchronously here

Otherwise I sometimes get:
[????????] x11 video output error: X11 request 2.0 failed with error
code 3:
 BadWindow (invalid Window parameter)
 X Error of failed request:  BadWindow (invalid Window parameter)
 Major opcode of failed request:  2 (X_ChangeWindowAttributes)
 Resource id in failed request:  0x1000027
 Serial number of failed request:  26
 Current serial number in output stream:  27