pfetch: wm support for Xorg

pfetch

@@ -668,6 +668,94 @@ get_memory() {
     log memory "${mem_used:-?}M / ${mem_full:-?}M" >&6
 }
 
+get_wm() {
+    case $os in
+        # Don't display window manager on macOS.
+        Darwin*) ;;
+
+        *)
+            # xprop can be used to grab the window manager's properties
+            # which contains the window manager's name under '_NET_WM_NAME'.
+            #
+            # The upside to using 'xprop' is that you don't need to hardcode
+            # a list of known window manager names. The downside is that
+            # not all window managers conform to setting the '_NET_WM_NAME'
+            # atom..
+            #
+            # List of window managers which fail to set the name atom:
+            # catwm, fvwm, dwm, 2bwm and monster.
+            #
+            # The final downside to this approach is that it does _not_
+            # support Wayland environments. The only solution which supports
+            # Wayland is the 'ps' parsing mentioned below.
+            #
+            # A more naive implementation is to parse the last line of
+            # '~/.xinitrc' to extract the second white-space separated
+            # element.
+            #
+            # The issue with an approach like this is that this line data
+            # does not always equate to the name of the window manager and
+            # could in theory be _anything_.
+            #
+            # This also fails when the user launches xorg through a display
+            # manager or other means.
+            #
+            #
+            # Another naive solution is to parse 'ps' with a hardcoded list
+            # of window managers to detect the current window manager (based
+            # on what is running).
+            #
+            # The issue with this approach is the need to hardcode and
+            # maintain a list of known window managers.
+            #
+            # Another issue is that process names do not always equate to
+            # the name of the window manager. False-positives can happen too.
+            #
+            # This is the only solution which supports Wayland based
+            # environments sadly. It'd be nice if some kind of standard were
+            # established to identify Wayland environments.
+            #
+            # pfetch's goal is to remain _simple_, if you'd like a "full"
+            # implementation of window manager detection use 'neofetch'.
+            #
+            # Neofetch use a combination of 'xprop' and 'ps' parsing to
+            # support all window managers (including non-conforming and
+            # Wayland) though it's a lot more complicated!
+
+            # Don't display window manager if X isn't running.
+            [ "$DISPLAY" ] || return
+
+            # This is a two pass call to xprop. One call to get the window
+            # manager's ID and another to print its properties.
+            command -v xprop && {
+                # The output of the ID command is as follows:
+                # _NET_SUPPORTING_WM_CHECK: window id # 0x400000
+                #
+                # To extract the ID, everything before the last space
+                # is removed.
+                id=$(xprop -root -notype _NET_SUPPORTING_WM_CHECK)
+                id=${id##* }
+
+                # The output of the property command is as follows:
+                # _NAME 8t
+                # _NET_WM_PID = 252
+                # _NET_WM_NAME = "bspwm"
+                # _NET_SUPPORTING_WM_CHECK: window id # 0x400000
+                # WM_CLASS = "wm", "Bspwm"
+                #
+                # To extract the name, everything before '_NET_WM_NAME = \"'
+                # is removed and everything after the next '"' is removed.
+                wm=$(xprop -id "$id" -notype -len 25 -f _NET_WM_NAME 8t)
+                wm=${wm##*_NET_WM_NAME = \"}
+                wm=${wm%%\"*}
+            }
+        ;;
+    esac
+
+    log wm "$wm" >&6
+}
+
+
 get_de() {
     # This only supports Xorg related desktop environments though
     # this is fine as knowing the desktop envrionment on Windows,