Launch Firefox from Steam Deck's "Gaming Mode".

firefox.sh

#!/bin/bash
##
## Launch Firefox from Steam Deck's "Gaming Mode".
##
## Although it doesn't provide a perfect browsing experience, this script
## at least makes sure that menus and windows appear as they're supposed to.
##
## INSTRUCTIONS:
##
## - Save this file to the ~/.local/bin directory.
##     - In Dolphin, click on the Menu button and enable "Show Hidden Files".
##       Go to your "Home" directory and open the ".local" folder.
##       Create a "bin" folder if needed, and save this file to it.
##     - Or, in Konsole, use the following commands:
##           mkdir -p ~/.local/bin
##           mv ~/Downloads/firefox.sh ~/.local/bin/firefox.sh
## - Mark the file as executable.
##     - In Dolphin, right-click the file and open Properties.
##       In the Permissions tab, enable the "Is executable" checkbox.
##     - Or, in Konsole, use the following command:
##           chmod +x ~/.local/bin/firefox.sh
## - Add the script to Steam as a non-Steam game.
##     - In the Games menu, select "Add a Non-Steam Game to My Library...".
##     - Click "BROWSE..." and navigate to "/home/deck/.local/bin".
##     - Change the "File type" from "Applications (*.desktop)" to "All Files".
##     - Select "firefox.sh", click "OPEN", then "ADD SELECTED PROGRAMS'.
## - Give the script a proper name in your Steam library.
##     - Navigate to the "firefox.sh" page in your Steam library.
##     - Click on the gear icon and select "Properties...".
##     - Use the first textbox to change the name to "Mozilla Firefox".
##
## You can use BoilR to give the "Mozilla Firefox" page proper icons and
## images from SteamGridDB.
##
## - Download and install BoilR from Flathub:
##   https://flathub.org/apps/details/io.github.philipk.boilr
## - Get an API key from SteamGridDB for BoilR.
##     - Sign in to SteamGridDB with your Steam account.
##       https://www.steamgriddb.com/login
##     - Copy the SteamGridDB API key for your account.
##       https://www.steamgriddb.com/profile/preferences/api
##     - In BoilR, go to "Settings" and paste your SteamGridDB API key into
##       the "Authentication key" field. Make sure to check "Download images".
##     - Click the floppy disk icon at the bottom of the window to save.
## - Set the SteamGridDB ID for "Mozilla Firefox" to download Steam Deck icons.
##   https://www.steamgriddb.com/game/5248361
##     - In BoilR, go to "Images" and click on "Mozilla Firefox".
##     - Click "Click here if the images are for a wrong game".
##     - Change the "SteamGridDB ID" to 5248361.
## - Set the grid image, hero image, and icon.
##     - In BoilR, go to "Images" and click on "Mozilla Firefox".
##     - Click on "Grid", "Hero", "Icon", etc. to select images.
##     - When you're done, click on "Import Games".
##     - Click on the button at the bottom of the window with the picture of an
##       arrow pointing from a game controller to the Steam icon to save your
##       changes.
## - Restart Steam to see the new images on the "Mozilla Firefox" library page.
##
## ----------------------------------------------------------------------------
##
## Copyright (c) 2022 Steven Brunwasser
##
## Permission is hereby granted, free of charge, to any person obtaining a
## copy of this software and associated documentation files (the "Software"),
## to deal in the Software without restriction, including without limitation
## the rights to use, copy, modify, merge, publish, distribute, sublicense,
## and/or sell copies of the Software, and to permit persons to whom the
## Software is furnished to do so, subject to the following conditions:
##
## The above copyright notice and this permission notice shall be included in
## all copies or substantial portions of the Software.
##
## THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
## IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
## FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
## THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
## LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
## FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
## DEALINGS IN THE SOFTWARE.

# Exit on any failure.
set -eo pipefail

# Check to make sure we have information about the screen.
if [ -z "${DISPLAY:-}" ]; then
    echo 'No $DISPLAY attached to the current session.' >&2
    exit 2
fi

# Check to make sure we're running in "Gaming Mode".
if [ -z "${GAMESCOPE_WAYLAND_DISPLAY:-}" ]; then
    # Run Firefox normally if we're in "Desktop Mode".
    exec /usr/bin/flatpak run \
        --arch=x86_64 --branch=stable \
        --file-forwarding --die-with-parent \
        --command=firefox org.mozilla.firefox
fi

# Point KDE to use our customized config files for "Gaming Mode".
export XDG_CONFIG_HOME=$HOME/.local/config/gamescope/firefox
# Make sure KDE uses the user's config values for default settings.
export XDG_CONFIG_DIRS=$HOME/.config:$XDG_CONFIG_DIRS

# Check to make sure our config directory exists.
if [ ! -e $XDG_CONFIG_HOME ]; then
    # Create the missing config directory.
    mkdir -p $XDG_CONFIG_HOME

    # Create a kwin config to hide title bars for maximized windows.
    cat >$XDG_CONFIG_HOME/kwinrc <<KWINRC
[Windows]
BorderlessMaximizedWindows=true
KWINRC

    # Save a window rule to force maximized windows.
    cat >$XDG_CONFIG_HOME/kwinrulesrc <<KWINRULES
[gamescope-fullscreen-windows]
Description=Fullscreen Windows
closeablerule=2
maximizehoriz=true
maximizehorizrule=2
maximizevert=true
maximizevertrule=2
minimizerule=2
noborder=true
noborderrule=2
position=0,0
positionrule=2
shaderule=2
wmclasscomplete=true
wmclassmatch=2
types=66051

[General]
count=2
rules=1,gamescope-fullscreen-windows
KWINRULES
fi

# Get information about the screen's resolution.
# We use this to make sure the desktop uses the full screen.
_DISPLAY_RESOLUTION="$(xdpyinfo | awk '/dimensions/ {print $2}')"

# Make sure all shared libraries are loaded in their default order.
unset LD_PRELOAD

# Launch Firefox in its own KDE environment.
exec kwin_wayland --no-lockscreen --drm \
    --width "${_DISPLAY_RESOLUTION%x*}" \
    --height "${_DISPLAY_RESOLUTION#*x}" \
    --xwayland --x11-display "${DISPLAY}" \
    --exit-with-session=" \
        /usr/bin/flatpak run \
            --arch=x86_64 --branch=stable \
            --file-forwarding --die-with-parent \
            --command=firefox org.mozilla.firefox"