Determine monitor in better way on bspwm and i3

Addresses #3

This ensures that -m will work even when the focused workspace on a
monitor is empty.

tdrop

@@ -146,7 +146,25 @@ update_geometry_settings_for_monitor() {
 	#    monitor IF the monitor has changed since the last time the dropdown
 	#    was used
 
-	# determine curent monitor
+	# it is conceivable that a user may want to use -m but not -a, so
+	# get the wm from with
+	# in this function
+	wm=$(get_window_manager)
+	if [[ $wm == bspwm ]]; then
+		current_monitor=$(bspc query -m -M)
+	elif [[ $wm == i3 ]]; then
+		# I'd rather not make jq a dependency
+		current_monitor=$(i3-msg -t get_workspaces | sed 's/{"num"/\n/g' | awk -F ',' '/focused":true/ {sub(".*output",""); gsub("[:\"]",""); print $1}')
+	fi
+
+	if [[ -n $current_monitor ]]; then
+		monitor_geo=$(xrandr --query | awk "/$current_monitor/ {gsub(\"primary \",\"\"); print \$3}")
+		x_begin=$(echo "$monitor_geo" | awk -F '+' '{print $2}')
+		y_begin=$(echo "$monitor_geo" | awk -F '+' '{print $3}')
+		x_width=$(echo "$monitor_geo" | awk -F 'x' '{print $1}')
+		y_height=$(echo "$monitor_geo" | awk -F 'x|+' '{print $2}')
+	else
+		# determine current monitor in generic (hacky) way
 		wininfo=$(xwininfo -id "$(xdotool getactivewindow)")
 		window_x=$(echo "$wininfo" | awk '/Absolute.*X/ {print $4}')
 		window_y=$(echo "$wininfo" | awk '/Absolute.*Y/ {print $4}')
@@ -165,6 +183,7 @@ update_geometry_settings_for_monitor() {
 				break
 			fi
 		done <<< "$monitors_info"
+	fi
 
 	# update x and y offsets, so that will appear on correct screen
 	# (required for some WMs apparently, but not for others)