Wrong mapping for Wacom Pad buttons
I have no clue if I'm in the right place with this. So forgive me if I'm not and give me a hint on who to confront with this bug I found.
The screen behind the "Map Buttons..." button found on the "Devices > Wacom Tablet > Tablet" page is not really usable for me. (I'm using a Wacom Intuos PT M 2). If I press the buttons on the top of my tablet they are supposed to light up in the UI. The problem is that only three of them cause a button in the UI to light up. Also the wrong ones light up. (E.g. pressing the top left one on my tablet causes the top right one on the screen to become light blue.) And on top of that only the button configurations of two of them actually work.
Considering the exact correspondence between pressing buttons on the tablet and UI buttons flashing up, the fact that one of them doesn't work at all and that the button action for one of them is ignored suggests that what the gnome-settings tool does is equivalent to:
$ xsetwacom set pad Button 1 "key A"
$ xsetwacom set pad Button 2 "key B"
$ xsetwacom set pad Button 3 "key C"
$ xsetwacom set pad Button 4 "key D"
Unsupported offset into 'Wacom Button Actions' property.
Note that the last command printed an error message. Also when testing this setup in a text editor it seems that the second line didn't have any effect. (I.e. only Cs and As are inserted to the document.)
I think the devs of the wacom driver have changed the button mapping to a different one over time. It's now using the button indices 3, 1, 9 and 8. Therefore the following works flawlessly:
$ xsetwacom set pad Button 3 "key A"
$ xsetwacom set pad Button 1 "key B"
$ xsetwacom set pad Button 9 "key C"
$ xsetwacom set pad Button 8 "key D"
^^ With this the buttons on my tablet now send the same characters as the labels in the vector graphic shipped with libwacom. Well, clearly someone is assuming the wrong button ids causing the gnome-settings UI not to work properly. However I can't tell if it's the gnome-settings app or libwacom or something else as I'm not very familiar with the source of either of these projects. But for me it seems to be most likely a problem with gnome-settings.
I hope this report leads someone to the right spot to be able to fix that annoying bug.