Make -m work on empty desktops for all WMs

When there is no active window, open the dropdown and use it to
determine the current monitor. This can result in delay before the
dropdown is resized. Closes #3.

README.md

@@ -45,7 +45,7 @@ Using the `-m`/`--monitor-aware` flag has two purposes. For those who use a sing
 
 For those who use multiple monitors, using `-m` will additionally alter the width and height options to correspond to the current monitor. This means that `-w 100%` will cause the dropdown to occupy the full width of the current monitor instead of spanning all monitors. Also, the `-m` option will automatically resize the dropdown when opening it on a different monitor if the width or height arguments are negative or percentages.
 
-Some window managers allow querying what the current monitor is (e.g. bspwm and i3), but for other window managers, tdrop determines the current monitor based on the position of the active window. This means that for window managers that have a concept of a focused but empty monitor, the `-m` option may not work properly on empty monitors. If you encounter this problem, please make an issue.
+Some window managers allow querying what the current monitor is (e.g. bspwm and i3), but for other window managers, tdrop determines the current monitor based on the position of the active window. For these window managers, if the desktop is empty, tdrop must wait for the dropdown to be created or mapped before getting the monitor info. This may cause a slight delay before the dropdown is properly resized. If `-m` does not work at all or there is a specific way to query for the current monitor in your window manager, please make an issue.
 
 See the manpage for more information.
 

tdrop

@@ -133,6 +133,13 @@ combine_map_post=false
 # in order to force resize the dropdown to the given width/height percentages
 # for the current monitor
 monitor_changed=false
+# used for -m option; at first tdrop assumes that there is a focused window
+# on the current desktop; if there isn't (and the WM doesn't have some way to
+# query the current monitor), this will be set to false, and tdrop will have to
+# find out the current monitor info after opening the dropdown
+# (currently, using xwininfo to find the position of a window is the only
+# WM-independent way I know to find out what the current monitor is)
+focused_window_exists=true
 
 #
 # Multiple Monitor Automatic Re-Sizing
@@ -168,9 +175,14 @@ update_geometry_settings_for_monitor() {
 		x_width=$(echo "$monitor_geo" | awk -F 'x' '{print $1}')
 		y_height=$(echo "$monitor_geo" | awk -F 'x|+' '{print $2}')
 	else
-		local wininfo window_x window_y monitors_info x_end y_end
-		# determine current monitor in generic (hacky) way
-		wininfo=$(xwininfo -id "$(xdotool getactivewindow)")
+		local wid wininfo window_x window_y monitors_info x_end y_end
+		# determine current monitor in generic way
+		wid=$(xdotool getactivewindow)
+		if [[ -z $wid ]]; then
+			# will try again after remapping or creating the dropdown
+			return 1
+		fi
+		wininfo=$(xwininfo -id "$wid")
 		window_x=$(echo "$wininfo" | awk '/Absolute.*X/ {print $4}')
 		window_y=$(echo "$wininfo" | awk '/Absolute.*Y/ {print $4}')
 		monitors_info=$(xrandr --query | awk '/ connected/ {gsub("primary ",""); print}')
@@ -513,10 +525,11 @@ wid_toggle() {
 			else
 				map_pre_command "$term"
 			fi
-			# update here so this doesn't cause a delay
+			# update here if possible so this doesn't cause a delay
 			# between the window being remapped and resized
 			if $monitor_aware; then
-				update_geometry_settings_for_monitor
+				update_geometry_settings_for_monitor || \
+					focused_window_exists=false
 			fi
 			if ! $combine_map_post; then
 				xdotool windowmap "$wid"
@@ -526,6 +539,10 @@ wid_toggle() {
 				map_post_command "$wid"
 			fi
 			maybe_cancel_auto_show "$wid"
+			if ! $focused_window_exists; then
+				# need to use dropdown as active window to get monitor info
+				update_geometry_settings_for_monitor
+			fi
 			# would be much too messy to integrate a resize into existing map_post commands
 			# or add for those WMs that don't even need an xdotool command
 			# cleaner to do after any map_post command with the downside of potential
@@ -538,8 +555,19 @@ wid_toggle() {
 		fi
 	else
 		# necessary to deal with negative width or height
-		if $monitor_aware; then
-			update_geometry_settings_for_monitor
+		# if creating on an empty desktop and can't determine the monitor,
+		# must set temporary values for negative width and/or height
+		local original_width original_height
+		if $monitor_aware && ! update_geometry_settings_for_monitor; then
+			focused_window_exists=false
+			if [[ $width =~ ^- ]]; then
+				original_width=$width
+				width=100%
+			fi
+			if [[ $height =~ ^- ]]; then
+				original_height=$height
+				height=100%
+			fi
 		fi
 		# make it
 		map_pre_command "$term"
@@ -563,6 +591,13 @@ wid_toggle() {
 				((count++))
 			done
 			map_post_command oneshot "$wid"
+			# update window dimensions if necessary
+			if ! $focused_window_exists; then
+				width=${original_width:-$width}
+				height=${original_height:-$height}
+				update_geometry_settings_for_monitor
+				set_geometry_for_monitor "$wid"
+			fi
 		fi
 	fi
 }