Proper multimonitor support (2nd try)

README.md

@@ -87,8 +87,4 @@ Systemd Unit file example (edit for your own use):
 
 Multiple Monitors
 -----------------
-There is a branch called dual monitor with support for multiple monitors. This
-branch uses a grey icon and text with outlines to make it visible on light and
-dark backgrounds (though it looks better on dark backgrounds). I am still
-working to get it looking just right right. The script is usable now, but it's
-under developement and things may change.
+This script fully supports multiple monitors. The lock and text are drawn on the center of each monitor.

lock

@@ -3,6 +3,80 @@
 # Dependencies: imagemagick, i3lock-color-git, scrot, wmctrl (optional)
 set -o errexit -o noclobber -o nounset
 
+# Determines the brightness of the screenshot
+# $1 - Image file to check
+# $2 - Arguments passed to 'convert'. For example this can be used to crop the image, to just sample a part of it
+get_brightness() {
+    # Quite fast way of getting a brightness value
+    convert "$1" +repage $2 -colorspace gray -format "%[fx:round(100*mean)]" info:
+}
+
+# Determines the width of the given text when processed using the text_options flag
+# $1 - The text to checked
+# Prints the text width in pixels to stdout
+get_text_width() {
+    # empty text or text containing only whitespace would throw an error so we just return zero
+    if [ -z "${1// }" ]; then
+        echo 0
+        return
+    fi
+    convert "${text_options[@]}" label:"$1" -format "%[fx:w]\n" info:
+}
+
+# Calculates the absolute positions for the lock and text or the given monitor, generates the command line arguemnts
+# for convert that apply the lock icon and the text to the proper locations and adds them to the decorations_params array
+# $1 - Monitor Width
+# $2 - Monitor Height
+# $3 - X Offset
+# $4 - Y Offset
+# Prints the brigthness in the center of the monitor to file descriptor 3
+# This is used to determine the average brightness in the centers of all the monitors and to then set the proper colors
+# for i3lock-color
+process_monitor() {
+    width=$1
+    height=$2
+    x_offset=$3
+    y_offset=$4
+
+    # center coordinates relative to the current monitor
+    x_mid=$((width / 2))
+    y_mid=$((height / 2))
+
+    # absolute X, Y coordinates of the top left edge of the text
+    x_text=$((x_offset + x_mid - (text_width / 2)))
+    y_text=$((y_offset + y_mid + 160))
+
+    # absolute X, Y coordinates of the top left edge of the icon
+    # The lock icon has dimensions 60x60, we subtract half of that from each dimension
+    # If the lock dimensions ever change, these values here need to be changed too
+    x_icon=$((x_offset + x_mid - 30))
+    y_icon=$((y_offset + y_mid - 30))
+
+    # Get brightness for the middle of the monitor
+    brightness="$(get_brightness "$image" "-crop 100x100+$x_icon+$y_icon")"
+
+    if [ "$brightness" -gt "$threshold" ]; then # bright background image and black text
+        text_color="black"
+        icon="$scriptpath/icons/lockdark.png"
+    else # dark background image and white text
+        text_color="white"
+        icon="$scriptpath/icons/lock.png"
+    fi
+
+    decoration_params+=(+repage)
+
+    if [ "$text_width" -ne 0 ]; then
+        # Only add text flags, if there actually is text
+        decoration_params+=("${text_options[@]}" -fill "$text_color" -annotate "+$x_text+$y_text" "$text")
+    fi
+
+    decoration_params+=("$icon" -geometry "+$x_icon+$y_icon" -composite)
+
+
+    # Write brightness to file descriptor
+    exec 3<<< "$brightness"
+}
+
 # get path where the script is located to find the lock icon
 scriptpath=$(readlink -f -- "$0")
 scriptpath=${scriptpath%/*}
@@ -11,9 +85,14 @@ hue=(-level "0%,100%,0.6")
 effect=(-filter Gaussian -resize 20% -define "filter:sigma=1.5" -resize 500.5%)
 # default system sans-serif font
 font=$(convert -list font | awk "{ a[NR] = \$2 } /family: $(fc-match sans -f "%{family}\n")/ { print a[NR-1]; exit }")
-image=$(mktemp --suffix=.png)
-shot=(import -window root)
+
+image="$(mktemp --suffix=.png)"
+
+# brightness value to compare to, everything above is considered white and everything below black
+threshold="40" 
+
 desktop=""
+shot=(import -window root)
 i3lock_cmd=(i3lock -i "$image")
 shot_custom=false
 
@@ -77,9 +156,9 @@ while true ; do
             esac ;;
         -t|--text) text=$2 ; shift 2 ;;
         -l|--listfonts)
-	    convert -list font | awk -F: '/Font: / { print $2 }' | sort -du | command -- ${PAGER:-less}
-	    exit 0 ;;
-	-n|--nofork) i3lock_cmd+=(--nofork) ; shift ;;
+            convert -list font | awk -F: '/Font: / { print $2 }' | sort -du | command -- ${PAGER:-less}
+            exit 0 ;;
+        -n|--nofork) i3lock_cmd+=(--nofork) ; shift ;;
         --) shift; shot_custom=true; break ;;
         *) echo "error" ; exit 1 ;;
     esac
@@ -89,32 +168,59 @@ if "$shot_custom" && [[ $# -gt 0 ]]; then
     shot=("$@");
 fi
 
-command -- "${shot[@]}" "$image"
-
-value="60" #brightness value to compare to
+text_options=(-font "$font" -pointsize 26)
+text_width=$(get_text_width "$text")
 
-color=$(convert "$image" -gravity center -crop 100x100+0+0 +repage -colorspace hsb \
-    -resize 1x1 txt:- | awk -F '[%$]' 'NR==2{gsub(",",""); printf "%.0f\n", $(NF-1)}');
+command -- "${shot[@]}" "$image"
 
-if [[ $color -gt $value ]]; then #white background image and black text
-    bw="black"
-    icon="$scriptpath/icons/lockdark.png"
+# All the arguments to be passed to convert, to add the lock and text to the monitors is collected here so that we can
+# apply them in a single call to convert
+decoration_params=()
+
+# We collect the brightness values from all the monitors and average them, from that we determine which flags to pass to
+# i3lock-color since the colors for i3lock-color cannot be specified per monitor. 
+# We could also just call get_brightness on the whole image but process_monitor samples only the center 
+# of the screen where the lock actually is, so we get a better value for the brightness
+sum_brightness=0
+num_monitors=0
+
+# Loop through all connected monitors (as reported by xrandr)
+# For each monitor the convert arguments to add the lock and text to that monitor are generated
+while read -r monitor; do
+    if [[ "$monitor" =~ ([0-9]+)x([0-9]+)\+([0-9]+)\+([0-9]+) ]]; then
+        width=${BASH_REMATCH[1]}
+        height=${BASH_REMATCH[2]}
+        x_offset=${BASH_REMATCH[3]}
+        y_offset=${BASH_REMATCH[4]}
+
+        # We get the return value from the function by using a new file descriptor
+        # The traditional approach of using $(process_monitor ...) and echo doesn't work because it forks into a 
+        # subshell and then process_monitor cannot access decoration_params
+        exec 3>&-
+        process_monitor "$width" "$height" "$x_offset" "$y_offset" && read -r brightness <&3
+        exec 3>&-
+
+        sum_brightness=$((brightness + sum_brightness))
+        num_monitors=$((num_monitors + 1))
+    fi
+done <<<"$(xrandr --verbose | grep "\bconnected\b")"
+
+convert "$image" "${hue[@]}" "${effect[@]}" "${decoration_params[@]}" "$image"
+
+avg_brightness=$((sum_brightness / num_monitors))
+
+if [ "$avg_brightness" -gt "$threshold" ]; then # Screenshot is rather bright, so we use dark colors
     param=("--textcolor=00000000" "--insidecolor=0000001c" "--ringcolor=0000003e" \
         "--linecolor=00000000" "--keyhlcolor=ffffff80" "--ringvercolor=ffffff00" \
         "--separatorcolor=22222260" "--insidevercolor=ffffff1c" \
         "--ringwrongcolor=ffffff55" "--insidewrongcolor=ffffff1c")
-else #black
-    bw="white"
-    icon="$scriptpath/icons/lock.png"
+else # Bright colors
     param=("--textcolor=ffffff00" "--insidecolor=ffffff1c" "--ringcolor=ffffff3e" \
         "--linecolor=ffffff00" "--keyhlcolor=00000080" "--ringvercolor=00000000" \
         "--separatorcolor=22222260" "--insidevercolor=0000001c" \
         "--ringwrongcolor=00000055" "--insidewrongcolor=0000001c")
 fi
 
-convert "$image" "${hue[@]}" "${effect[@]}" -font "$font" -pointsize 26 -fill "$bw" -gravity center \
-    -annotate +0+160 "$text" "$icon" -gravity center -composite "$image"
-
 # If invoked with -d/--desktop, we'll attempt to minimize all windows (ie. show
 # the desktop) before locking.
 ${desktop} ${desktop:+-k on}