Implement different keyboard layouts for individual windows

[lenemter]

Fixes #180

[leonardo-lemos]

I tested with two layouts: pt_br and en_US (intl.). When I set a layout (eg. pt_br) and use it in a window, I can't change window layout to another layout (eg. en_US), Gala always reverts the layout to the first one.

[lenemter]

@leonardo-lemos what do you mean 'Gala always reverts the layout to the first one'? It works fine for me

[leonardo-lemos]

@lenemter There are two problems to me:

1. I can't change layout using the keyboard indicator, because if I'm using a layout A in a window and try to change to a layout B, the indicator always reverts state to layout A
2. If I'm using terminal with layout A and and code with layout A, then go back to terminal and change to layout B using a keyboard shortcut, code will be set to use layout B too.

[lenemter]

@leonardo-lemos I fixed interaction with the keyboard indicator. But I cannot reproduce the second issue you have. Can you check again now, maybe it got fixed on your side?

[leonardo-lemos]

@lenemter It works as expected when changing layouts using the indicator, but doesn't work properly when changing layouts using the keyboard (using the change layout shortcut). When I change layout using the shortcut, it changes layout for all the windows.

[lenemter]

@leonardo-lemos Can you provide steps to reproduce? It works fine for me ¯\_(ツ)_/¯

[leonardo-lemos]

@lenemter Sure

2025-06-09.13-05-51.mp4

1. Make sure you have two keyboard layouts enabled: Portuguese (Brazil) and English (US).
2. Open a window (e.g., a text editor or browser) with the English (US) layout active.
3. Type something. In my case, I pressed the ´ key on my pt-br keyboard, which corresponds to [ in the en-us layout.
4. Switch to a different window.
5. Change the keyboard layout using the keyboard shortcut (e.g., Alt + Shift).
6. Confirm that the layout has switched to pt-br. Type ´ and verify that it appears correctly on the screen.
7. Return to the first window. You'll see that the keyboard layout has also changed to pt-br, even though it was previously set to en-us.

This seems to be an issue with Gala or the keyboard layout indicator, rather than something caused by the changes in this PR. Could you confirm?