313 lines
8.2 KiB
Markdown
313 lines
8.2 KiB
Markdown
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title = "Vim-like Layer for Xorg and Wayland"
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date = "2020-08-25"
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author = "Ceda EI"
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tags = ["xorg", "wayland", "vim"]
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keywords = ["xorg", "wayland", "vim"]
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description = "Create a layer of shortcuts with xkb for Xorg and Wayland"
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showFullContent = false
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+++
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# The Goal
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## Insert Mode
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## Normal Mode
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Inspired by vim, I wanted to create a layer on top of my keyboard which worked
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like a shortcut layer. So, to start off, I found out about XKB[^1]. XKB is the
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Xorg Keyboard Extension which tells Xorg on how to react to input from
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keyboard. After reading through some source code, I found out that Xorg has
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support for function keys F1 - F35[^2]. The general idea here was:
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- Create an insert mode layout for text input.
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- Replace keys with relevant keys in normal mode (e.g. replace j with Down) and
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for keys that require executing a command, replace then with a function key
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above F12 (e.g. replace q with F13).
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- Bind all the function keys above F12 to the respective functions.
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To start off, I began a fresh Xorg session with nothing modifying the keys
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(removed `xmodmap` from startup) and first dumped the current layout into a
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file.
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```bash
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xkbcomp $DISPLAY ~/.xkb/insert.xkb
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```
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This was my starting point. I made changes to this file which were common to
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both Insert and Normal mode. e.g. replaced `Caps Lock` with `Ctrl` and made
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`Shift+Caps Lock` `Caps Lock`. Also, I unbound `Alt_R` as a modifier so that I
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could use that as a switch between Normal and Insert Mode.
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Here is a diff between the original layout and Insert mode.
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```
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1323c1321
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< key <CAPS> { [ Caps_Lock ] };
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---
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> key <CAPS> { [ Control_L, Caps_Lock ] };
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1551c1549
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< modifier_map Lock { <CAPS> };
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---
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> modifier_map Control { <CAPS> };
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1555d1552
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< modifier_map Mod1 { <RALT> };
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```
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Next, I copied `~/.xkb/insert.xkb` to `~/.xkb/normal.xkb`. I replaced keys as
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per the plan.
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Here is a diff between Insert mode and Normal mode.
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```diff
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1200c1200
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< symbols[Group1]= [ q, Q ]
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---
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> symbols[Group1]= [F13]
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1204c1204
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< symbols[Group1]= [ w, W ]
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---
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> symbols[Group1]= [F14]
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1208c1208
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< symbols[Group1]= [ e, E ]
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---
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> symbols[Group1]= [F15]
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1212c1212
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< symbols[Group1]= [ r, R ]
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---
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> symbols[Group1]= [F16]
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1216c1216
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< symbols[Group1]= [ t, T ]
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---
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> symbols[Group1]= [F17]
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1220c1220
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< symbols[Group1]= [ y, Y ]
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---
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> symbols[Group1]= [F18]
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1224c1224
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< symbols[Group1]= [ u, U ]
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---
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> symbols[Group1]= [F19]
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1228c1228
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< symbols[Group1]= [ i, I ]
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---
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> symbols[Group1]= [Alt_R]
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1232c1232
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< symbols[Group1]= [ o, O ]
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---
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> symbols[Group1]= [F20]
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1236c1236
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< symbols[Group1]= [ p, P ]
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---
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> symbols[Group1]= [F21]
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1244c1244
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< symbols[Group1]= [ a, A ]
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---
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> symbols[Group1]= [F22]
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1248c1248
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< symbols[Group1]= [ s, S ]
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---
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> symbols[Group1]= [Delete]
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1252c1252
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< symbols[Group1]= [ d, D ]
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---
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> symbols[Group1]= [BackSpace]
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1256c1256
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< symbols[Group1]= [ f, F ]
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---
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> symbols[Group1]= [Home]
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1260c1260
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< symbols[Group1]= [ g, G ]
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---
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> symbols[Group1]= [End]
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1264c1264
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< symbols[Group1]= [ h, H ]
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---
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> symbols[Group1]= [Left]
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1268c1268
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< symbols[Group1]= [ j, J ]
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---
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> symbols[Group1]= [Down]
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1272c1272
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< symbols[Group1]= [ k, K ]
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---
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> symbols[Group1]= [Up]
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1276c1276
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< symbols[Group1]= [ l, L ]
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---
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> symbols[Group1]= [Right]
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1285c1285
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< symbols[Group1]= [ z, Z ]
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---
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> symbols[Group1]= [F23]
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1289c1289
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< symbols[Group1]= [ x, X ]
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---
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> symbols[Group1]= [F24]
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1293c1293
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< symbols[Group1]= [ c, C ]
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---
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> symbols[Group1]= [F25]
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1297c1297
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< symbols[Group1]= [ v, V ]
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---
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> symbols[Group1]= [F26]
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1301c1301
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< symbols[Group1]= [ b, B ]
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---
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> symbols[Group1]= [F27]
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1305c1305
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< symbols[Group1]= [ n, N ]
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---
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> symbols[Group1]= [Next]
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1309c1309
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< symbols[Group1]= [ m, M ]
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---
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> symbols[Group1]= [Prior]
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```
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At this point, `normal.xkb` file defines the following layout.
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Now, we need a script that switches between layouts. To load an layout in Xorg, we use
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```bash
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xkbcomp ~/.xkb/normal.xkb "$DISPLAY"
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```
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Sway supports this via the input command in the following form.
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```bash
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swaymsg input '*' xkb_file ~/.xkb/normal.xkb
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```
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The following script cycles through the layouts when it is called. It also
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allows to add more layouts later (just add them to layouts array and it will
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cycle in the order of the array).
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```bash
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#!/usr/bin/env bash
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# Usage: xkb_swapper.sh [layout_name]
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function set_layout() {
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echo "Setting layout to $1"
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if [[ -v WAYLAND_DISPLAY ]]; then
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swaymsg input '*' xkb_file ~/.xkb/"$1".xkb
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else
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xkbcomp ~/.xkb/"$1".xkb "$DISPLAY"
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fi
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echo "$1" > ~/.cache/xkb-curr-"$DISPLAY"
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}
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layouts=(insert normal)
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current_layout=$(cat ~/.cache/xkb-curr-"$DISPLAY" || echo "")
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if [[ $1 != "" ]]; then
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set_layout "$1"
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exit
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fi
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if [[ $current_layout == "" ]]; then
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echo "No current layout found!"
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set_layout "${layouts[0]}"
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fi
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i=0
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while [[ $i -lt ${#layouts[@]} ]]; do
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if [[ $current_layout == "${layouts[$i]}" ]]; then
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new_idx="$((i+1))"
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if [[ $new_idx -eq ${#layouts[@]} ]]; then
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set_layout "${layouts[0]}"
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else
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set_layout "${layouts[$new_idx]}"
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fi
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exit
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fi
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((i++))
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done
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echo "Current Layout doesn't exist!"
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set_layout "${layouts[0]}"
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```
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The above script works with all Xorg based DE/WMs as well as Sway (wayland
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compositor). I saved it as `xkb_swapper.sh` in my `PATH`. Calling the script
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without any argument cycles through the layouts. If arguments are passed, the
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first argument is taken as layout name and layout is changed to that.
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The last step is binding the function keys and `Alt_R` to commands to execute.
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Here are some of the parts of my i3 config that bind the function keys.
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```
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bindsym Alt_R exec xkb_swapper.sh
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bindsym 0xffca kill
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bindsym 0xffcf exec volchange -5
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bindsym 0xffd0 exec volchange +5
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bindsym 0xffd1 exec brightness -200
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bindsym 0xffd2 exec brightness +200
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bindsym 0xffcb exec mpc prev
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bindsym 0xffcc exec mpc toggle
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bindsym 0xffcd exec mpc next
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```
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`i3` doesn't seem to accept `F13` - `F35` as keynames however it accepts the
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keycodes[^2]. Here is a small list for easy access.
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```
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0xffbe F1
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0xffbf F2
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0xffc0 F3
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0xffc1 F4
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0xffc2 F5
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0xffc3 F6
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0xffc4 F7
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0xffc5 F8
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0xffc6 F9
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0xffc7 F10
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0xffc8 F11
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0xffc9 F12
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0xffca F13
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0xffcb F14
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0xffcc F15
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0xffcd F16
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0xffce F17
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0xffcf F18
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0xffd0 F19
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0xffd1 F20
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0xffd2 F21
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0xffd3 F22
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0xffd4 F23
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0xffd5 F24
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0xffd6 F25
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0xffd7 F26
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0xffd8 F27
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0xffd9 F28
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0xffda F29
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0xffdb F30
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0xffdc F31
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0xffdd F32
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0xffde F33
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0xffdf F34
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0xffe0 F35
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```
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# Bonus: Displaying the current mode in your bar
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The script stores the mode in `~/.cache/xkb-curr-$DISPLAY`. `cat` that and
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wrap in your bar's config. Here is my config for
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[i3status-rust](https://github.com/greshake/i3status-rust).
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```toml
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[[block]]
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block = "custom"
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command = "echo -en '\\uf11c '; cat ~/.cache/xkb-curr-$DISPLAY"
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interval = 0.5
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```
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[^1]: As always, the [Arch Wiki page on XKB](https://wiki.archlinux.org/index.php/X_keyboard_extension) is a nice place to start.
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[^2]: You can find all the defined keys in `/usr/include/X11/keysymdef.h`.
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