hyprland-wiki/pages/Configuring/Environment-variables.md

As [aforementioned](../../Getting-Started/Master-Tutorial/#launching-hyprland-part-1), it's 
useful using a wrapper to launch Hyprland. Whether you start Hyprland through TTY or a Display 
Manager, it is always suggested to use one. As such, you can pass certain environment 
variables to improve Wayland compatibility, or simply change certain aspects of your desktop.

Please avoid putting those environment variables in /etc/environment. That will cause all
sessions (including Xorg ones) to pick up your wayland-specific environment on traditional
Linux distros.

# XDG Specifications

- `XDG_CURRENT_DESKTOP=Hyprland`
- `XDG_SESSION_TYPE=wayland`
- `XDG_SESSION_DESKTOP=Hyprland`

XDG specific environment variables are often detected through portals and applications that may
set those for you, however it is a good idea to provide them in your wrapper script as a fail-safe.

# QT Variables

- `QT_AUTO_SCREEN_SCALE_FACTOR=1` - [(From the QT documentation)](https://doc.qt.io/qt-5/highdpi.html)
enables automatic scaling, based on the monitor's pixel density
- `QT_QPA_PLATFORM="wayland;xcb"` - Tell QT applications to use the Wayland backend, and fall back to x11 if Wayland is unavailable
- `QT_WAYLAND_DISABLE_WINDOWDECORATION=1` - Disables window decorations on QT applications
- `QT_QPA_PLATFORMTHEME=qt5ct` - Tells QT based applications to pick your theme from qt5ct, use with Kvantum.

# NVIDIA Specific

To force GBM as a backend, set the following environment variables:

- `GBM_BACKEND=nvidia-drm`
- `__GLX_VENDOR_LIBRARY_NAME=nvidia`

> See [Archwiki Wayland Page](https://wiki.archlinux.org/title/Wayland#Requirements) for more details on those variables.

- `LIBVA_DRIVER_NAME=nvidia` - Hardware acceleration on NVIDIA GPUs

> See [Archwiki Hardware Acecleration Page](https://wiki.archlinux.org/title/Hardware_video_acceleration)
> for details and necessary values before setting this variable.

- `__GL_GSYNC_ALLOWED` - Controls if G-Sync capable monitors should use Variable Refresh Rate (VRR)

> See [Nvidia Documentation](https://download.nvidia.com/XFree86/Linux-32bit-ARM/375.26/README/openglenvvariables.html) for details.

- `__GL_VRR_ALLOWED` - Controls if Adaptive Sync should be used. Recommended to set as "0" to avoid having problems on some games.

- `WLR_DRM_NO_ATOMIC=1` - use legacy DRM interface instead of atomic mode setting. Might fix flickering issues.

# Toolkit Backend Variables

- `SDL_VIDEODRIVER=wayland` - Run SDL2 applications on Wayland. Remove or set to x11 if games that provide older versions of SDL cause
  compatibility issues
- `_JAVA_AWT_WM_NONEREPARENTING=1` - Fix possibly broken Java applications. Set to 1 until Wakefield is available.
- `CLUTTER_BACKEND="wayland"` - Clutter package already has wayland enabled, this variable will force Clutter applications
  to try and use the Wayland backend

- `GDK_BACKEND` - Force backend for wayland-enabled GTK3 and GTK4 backends. Available options are "wayland" or "x11". If GTK XWayland
  applications cause issues when set to "wayland", try "wayland,x11"

# Theming Related Variables

- `GTK_THEME` - Set a GTK theme manually, for those who want to avoid appearance tools such as lxappearance or nwg-look
- `XCURSOR_THEME` - Set your cursor theme. The theme needs to be installed and readable by your user.
- `XCURSOR_SIZE` - Set cursor size. See [here](../../FAQ/) for why you might want this variable set.