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The Alt+Shift issue

Making a place for discussion and brainstorming about what to do about the Alt+Shift issue, which is some what complicated, and might impact a lot of users.

Background

The problem

Alt+shift doesn't work as a shortcut (with the default keymap). Many users like to use this for layout switching, it appears.

Why?

By default, xkeyboard-config maps shifted alt to meta, so kglobalacceld gets meta events instead of alt events. (On x11, xev also reports meta keyPress when alt is pressed with shift held down). Our shortcut handling depends on Qt keycodes, which are converted from x11 keysyms.

Possible Solutions

Push for an upstream change in xkeyboard-config and tell distros to apply that patch.

Remove that default mapping for shifted alt to meta.

See https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/issues/488 for upstream discussion.

Pros

No code changes needed on our part.

Cons

It will probably be very hard to change something that has been around for more than twenty years.. (e.g., see https://gitlab.freedesktop.org/xkeyboard-config/xkeyboard-config/-/blob/9bbda6bfbcc29a575ea3b5cb7bd2553767e80d53/symbols/pc#L216). Maybe it is needed in some weird use case?

For modifier-keys used in shortcuts, use the unshifted keysyms

Pros

Immediately fixes the problem, requiring only changes on our end.

Cons

Needs to add special case handling code to kglobalacceld and maybe kwin, some what increasing code complexity.

For all shortcuts, use the unshifted keysyms

Store and trigger all shortcuts including shift as shift+unshifted key sym, instead of shifted key sym. E.g., Meta+! will be stored and triggered as Meta+Shift+1.

Pros

Makes user-defined shortcuts involving shift displayed in a friendlier manner (BUG: 434988)

Cons

Unclear how such shortcuts should work across different layouts. E.g., if a default shortcut is set to Ctrl++, what should we do when + is a shifted symbol in the layout? In some layouts + is a shifted symbol, and in some layouts it is not.

Implement support for shortcuts using native keycodes

Native keycodes are generated by the OS and are independent of the keymap. They are exposed as QKeyEvent->nativeScanCode().

Pros

  • Would make shortcuts more consistent for users who switch layouts (e.g., BUG: 453661)
  • Add ability to differentiate between left/right modifiers
  • Fixes BUG: 422401

Cons

  • Requires changes in frameworks/kglobalaccel, and many of its callers
  • Requires designing new UI
  • Probably not doable by 6.2, maybe 6.3 is feasible.

Pros

Immediately fixes the problem, requiring only changes on our end.

See also

cc @odeda @vvova @zhumarin @teams/usability @ilyabizyaev and kwin folks @vladz @zamundaaa

Edited by Yifan Zhu