picom-trans: Add inline `--help` output and update manpage

Fixes: #513

bin/picom-trans

@@ -23,6 +23,26 @@
 #   $ picom-trans -c --delete
 # Reset all windows
 #   $ picom-trans --reset
+print_usage() {
+  echo "Usage: $0 [options] [+|-]opacity"
+  echo ""
+  echo "Options:"
+  echo "  -h, --help                Print this help message."
+  echo "  -o, --opacity OPACITY     Specify the new opacity value in range 1-100 for the window. If"
+  echo "                            prefixed with + or -, increment or decrement from the target"
+  echo "                            window’s current opacity."
+  echo ""
+  echo "Actions:"
+  echo "  -g, --get                 Print the target window's opacity."
+  echo "  -d, --delete              Delete opacity of the target window."
+  echo "  -r, --reset               Reset opacity for all windows."
+  echo ""
+  echo "Window Selection:"
+  echo "  -s, --select              Select target window with mouse cursor. (DEFAULT)"
+  echo "  -c, --current             Select the currently active window as target."
+  echo "  -n, --name WINDOW_NAME    Specify and try to match a window name."
+  echo "  -w, --window WINDOW_ID    Specify the window id of the target window."
+}
 
 case "$0" in
   *compton-trans*)  echo "Warning: compton has been renamed, please use picom-trans instead" >& 2;;
@@ -34,6 +54,11 @@ if test -z "$(command -v xprop)" -o -z "$(command -v xwininfo)"; then
   exit 1
 fi
 
+if test $# -eq 0; then
+  print_usage >& 2
+  exit 1
+fi
+
 # Variables
 active=
 wprefix=
@@ -62,10 +87,10 @@ while test $# -gt 0; do
   OPTIND=1
 
   # Read options
-  while getopts 'scrdgn:w:o:-:' option "$@"; do
+  while getopts 'hscrdgn:w:o:-:' option "$@"; do
     if test "$option" = '-'; then
       case "$OPTARG" in
-        select | current | reset | delete | get)
+        help | select | current | reset | delete | get)
           v=''
         ;;
         name | window | opacity)
@@ -84,6 +109,7 @@ while test $# -gt 0; do
       OPTARG=$v
     fi
     case "$option" in
+      h) print_usage; exit 0 ;;
       s) wprefix=''; window='' ;;
       c)
         active=$(xprop -root -notype _NET_ACTIVE_WINDOW \

man/picom-trans.1.asciidoc

@@ -21,20 +21,29 @@ DESCRIPTION
 
 OPTIONS
 -------
-*-w* 'WINDOW_ID'::
+*-w*, *--window*='WINDOW_ID'::
 Specify the window id of the target window.
 
-*-n* 'WINDOW_NAME'::
+*-n*, *--name*='WINDOW_NAME'::
 Specify and try to match a window name.
 
-*-c*::
+*-c*, *--current*::
 Specify the currently active window as target. Only works if EWMH '_NET_ACTIVE_WINDOW' property exists on root window.
 
-*-s*::
+*-s*, *--select*::
 Select target window with mouse cursor. This is the default if no window has been specified.
 
-*-o* 'OPACITY'::
-Specify the new opacity value for the window. This value can be anywhere from 1-100. If it is prefixed with a plus or minus (+/-), this will increment or decrement from the target window's current opacity instead. 
+*-o*, *--opacity*='OPACITY'::
+Specify the new opacity value for the window. This value can be anywhere from 1-100. If it is prefixed with a plus or minus (+/-), this will increment or decrement from the target window's current opacity instead.
+
+*-g*, *--get*::
+Print the target window's opacity instead of setting it.
+
+*-d*, *--delete*::
+Delete opacity of the target window instead of setting it.
+
+*-r*, *--reset*::
+Reset opacity for all windows instead of setting it.
 
 EXAMPLES
 --------
@@ -75,6 +84,18 @@ picom-trans -c +5
 picom-trans -c -- -5
 ------------
 
+* Delete current window's opacity:
++
+------------
+picom-trans -c --delete
+------------
+
+* Reset all windows:
++
+------------
+picom-trans --reset
+------------
+
 BUGS
 ----
 Please submit bug reports to <https://github.com/yshui/picom>.