Use the user's keyboard layout from the x11 system

[TristanCacqueray]

This change uses xkbcommon to decode the key utf8 value based on the user's current layout. The implementation is adapted from the x11rb's xkbcommon-example.

[prokopyl]

Hi! And thanks for this PR! 🙂

I have yet to delve into the details of the XKB implementation, but one issue I see is that the xkbcommon-rs crate links directly against the xkbcommon library, which would mean hosts would fail to load a plugin altogether.

It's for this reason we have moved to using x11-dl for instance. I think this should use
xkbcommon-dl instead (which is also what winit uses).

There's also been quite a few changes to the X11 codebase since you first submitted this PR, so if you have the time to rebase and update it, it would be very helpful!

[TristanCacqueray]

Hey, alas I'm not sure how to get the keymap with xkbcommon-dl. Previously we could use get_core_keyboard_device_id, but now it looks like we need a name (e.g. for xkb_keymap_new)?

[prokopyl]

Hey, alas I'm not sure how to get the keymap with xkbcommon-dl. Previously we could use get_core_keyboard_device_id, but now it looks like we need a name (e.g. for xkb_keymap_new)?

So it looks like xkbcommon-dl has a x11 feature that exposes xkb_x11_get_core_keyboard_device_id & other XCB functions that we need. It's just that they are not shown on docs.rs (probably because they haven't configured the x11 feature to show up there), but it is available there!

[TristanCacqueray]

@prokopyl thanks, that makes sense now. So I updated the PR and it seems to work as expected: in the open_window example, using a french layout, pressing the keycode for 2 emit the proper é Character. To be honest I'm not super familiar with xkbcommon, and even less with these -dl variants, so I'd be happy to rework this change if needed.

Do we need a safe fallback in case xkbcommon_option is None, e.g. to handle a missing libxkbcommon-x11.so ?

[TristanCacqueray]

I also confirm this works downstream, e.g. through https://codeberg.org/TristanCacqueray/egui-baseview/src/branch/xkbfix

[prokopyl]

@prokopyl thanks, that makes sense now. So I updated the PR and it seems to work as expected: in the open_window example, using a french layout, pressing the keycode for 2 emit the proper é Character. To be honest I'm not super familiar with xkbcommon, and even less with these -dl variants, so I'd be happy to rework this change if needed.

Do we need a safe fallback in case xkbcommon_option is None, e.g. to handle a missing libxkbcommon-x11.so ?

Sweet, thanks! I have tested it and it works pretty much as expected on my French keyboard. 🙂

I think a fallback is always good to have yes. xkbcommon is pretty much ubiquitous on destkop Linux OSes, but it's Linux so there's no guarantee.
To me the fallback could be as simple as just using the previous behavior (from before this PR). That way it would fall back to pretty much raw key-codes that only work for QWERTY, which is good enough in my opinion.

[TristanCacqueray]

@prokopyl please let me know if this PR needs more change, I'm looking forward getting this integrated. Thanks!