commands/display/optimize-display-scaling.md

Optimize Display Scaling

You are helping the user configure HiDPI scaling and fractional scaling for optimal display clarity.

Task

1. Check current display information:

   # Display server type
   echo $XDG_SESSION_TYPE
   
   # Current resolution and size
   kscreen-doctor -o  # Wayland/KDE
   # OR
   xrandr --query  # X11
   
   # Calculate DPI
   xdpyinfo | grep -B 2 resolution  # X11
   

2. Determine optimal scaling:

   • Display resolution
   • Physical size (diagonal in inches)
   • Calculate PPI: sqrt(width² + height²) / diagonal_inches
   • Recommended scaling:
     • PPI < 110: 100% (1x)
     • PPI 110-140: 125% (1.25x)
     • PPI 140-180: 150% (1.5x)
     • PPI 180-220: 200% (2x)
     • PPI > 220: 250% or higher

3. For KDE Plasma (Wayland or X11):

   # Set global scale factor (Wayland)
   kscreen-doctor output.DP-1.scale.1.5
   
   # Or use GUI
   kcmshell6 kcm_kscreen
   

   Via settings file:

   # Edit KDE scaling
   kwriteconfig6 --file kdeglobals --group KScreen --key ScaleFactor 1.5
   kquitapp6 plasmashell && kstart plasmashell
   

4. For GNOME (Wayland):

   # Enable fractional scaling
   gsettings set org.gnome.mutter experimental-features "['scale-monitor-framebuffer']"
   
   # Set scale factor (200% = 2.0)
   gsettings set org.gnome.desktop.interface scaling-factor 2
   

5. For X11 systems (general):

   # Set Xft DPI
   echo "Xft.dpi: 144" >> ~/.Xresources
   xrdb -merge ~/.Xresources
   
   # Set scale factor for Qt applications
   export QT_SCALE_FACTOR=1.5
   
   # Set scale factor for GTK applications
   export GDK_SCALE=2
   export GDK_DPI_SCALE=0.5
   

6. Configure per-application scaling:

   # For specific Qt apps
   QT_SCALE_FACTOR=1.5 application-name
   
   # Add to .bashrc or application launcher
   echo 'export QT_SCALE_FACTOR=1.5' >> ~/.bashrc
   

7. Adjust font DPI:

   # KDE
   kwriteconfig6 --file kcmfonts --group General --key forceFontDPI 144
   
   # GNOME
   gsettings set org.gnome.desktop.interface text-scaling-factor 1.25
   

8. Handle cursor size:

   # Set cursor size
   gsettings set org.gnome.desktop.interface cursor-size 32  # GNOME
   kwriteconfig6 --file kcminputrc --group Mouse --key cursorSize 32  # KDE
   

Verify Configuration

1. Check current settings:

   echo $QT_SCALE_FACTOR
   echo $GDK_SCALE
   gsettings get org.gnome.desktop.interface scaling-factor  # GNOME
   

2. Test applications:

   • Open various applications (browser, terminal, file manager)
   • Check text clarity
   • Verify UI element sizes
   • Test both Qt and GTK applications

3. Log out and back in to apply system-wide changes

Troubleshooting

• Blurry applications: Some apps don't support fractional scaling on X11
• Inconsistent scaling: Mix of Qt and GTK apps may scale differently
• Wayland vs X11: Wayland generally handles fractional scaling better
• XWayland apps: May appear blurry on Wayland with fractional scaling

Solutions:

# Force XWayland scaling
kwriteconfig6 --file kwinrc --group Xwayland --key Scale 1.5

# Disable fractional scaling for specific apps
env QT_SCALE_FACTOR=1 application-name

Notes

• Wayland provides better fractional scaling support than X11
• Some applications may require restart to apply scaling
• Integer scaling (1x, 2x) is sharper than fractional (1.25x, 1.5x)
• Consider display distance when choosing scale factor
• Multi-monitor setups with different DPI may require per-monitor scaling