meta: Change cursor size based on DPI

Now that I figured out how to change cursor size for all applications
and not just a select few, restarting the X session to use a new cursor
size is no longer necessary.

rofi/.config/rofi/launch.sh

@@ -11,10 +11,45 @@
 # respects its theming even when XDG_CURRENT_DESKTOP is not set to it
 # (through settings.ini).
 
+# Note that the xcursor size is specified with:
+#
+#   1. The X server resource database (xrdb), of which cursor size is
+#      only applied BEFORE your window manager starts
+#   2. The xsetroot command, which affects the cursor shown on the root
+#      window (your desktop)
+#   3. The XCURSOR_SIZE environment variable, which affects the current
+#      program
+#
+# There are a few things to take away from this:
+#
+#   1. The root window (desktop) cursor size MUST be changed with xsetroot
+#   2. KDE applications will honor XCURSOR_SIZE but NOT xsetroot
+#   3. GTK applications will honor xsetroot but NOT XCURSOR_SIZE
+#
+# Additionally,
+#
+#   4. SOME X applications require XCURSOR_SIZE to be set and will NOT
+#      honor xsetroot
+#   5. SOME X applications require xsetroot to be set and will NOT
+#      honor XCURSOR_SIZE
+#
+# So for a consistent variable cursor DPI environment, one has to set BOTH
+# xsetroot and XCURSOR_SIZE
+#
+# Note that existing windows will NOT have their X cursor size changed
+# if they don't depend on xsetroot. Because of this, and because of the
+# fact that active windows will not handle DPI changes anyway, you should
+# probably have no GUIs running when switching DPI.
+
 ROFI_DPI=$(xrdb -query | grep Xft.dpi | cut -f 2)
 ROFI_SCALE=$(expr $ROFI_DPI / 96)
 ROFI_DPI_SCALE=$(awk "BEGIN { print "1/$ROFI_SCALE" }")
 
+CURSOR_THEME=${XCURSOR_THEME:-breeze_cursors}
+CURSOR_SIZE=$((16 * $ROFI_SCALE))
+
+xsetroot -xcf "/usr/share/icons/$CURSOR_THEME/cursors/left_ptr" "$CURSOR_SIZE"
+
 env \
   XDG_CURRENT_DESKTOP="KDE" \
   QT_AUTO_SCREEN_SCALE_FACTOR="0" \
@@ -22,6 +57,7 @@ env \
   QT_SCREEN_SCALE_FACTORS="VGA-1=$ROFI_SCALE;" \
   GDK_SCALE="$ROFI_SCALE" \
   GDK_DPI_SCALE="$ROFI_DPI_SCALE" \
+  XCURSOR_SIZE="$CURSOR_SIZE" \
   rofi \
     -show drun \
     -dpi "$ROFI_DPI"

xeventbind/.config/xeventbind/on-resolution-change.sh

@@ -3,6 +3,8 @@
 # Get the host width
 HOST_WIDTH=$(bspc query -T -m | jq '.rectangle.width')
 
+CURSOR_THEME=${XCURSOR_THEME:-breeze_cursors}
+
 # Determine the DPI based on screen width
 if [ "$HOST_WIDTH" -eq "1920" ]; then
   X_DPI=96
@@ -18,6 +20,13 @@ fi
 # If the DPI needs to be changed, change it
 if [ "$X_DPI" ]; then
   echo "Xft.dpi:$X_DPI" | xrdb -merge
+
+  # Change the X cursor size as well
+  # NOTE: For full effect, this needs to be used in combination with XCURSOR_SIZE.
+  # NOTE: ($X_DPI / 6) here means that 4k will use cursor size 32, so it will appear
+  #       about half the size of the 1080p cursor. If this is not what you want, use
+  #       cursor size 64 instead.
+  xsetroot -xcf "/usr/share/icons/$CURSOR_THEME/cursors/left_ptr" "$(($X_DPI / 6))"
 fi
 
 # Reload polybar with the new width / DPI