Add command line flag to directly open in color picker mode

Add the command line flag `--pick-color` to open the
application directly in color picking mode. This could
be helpful in setting up keybindings.

Add documentation for the option.

README.md

@@ -32,6 +32,18 @@ flatpak install https://flatpak.elementary.io/repo/appstream/com.github.phoneyba
 Flatpak is the recommended method of installation, however if you don't want
 to use flatpak you can always build from source using the build instructions.
 
+## Usage
+If installed as flatpak the program can be launched using
+```
+flatpak run com.github.phoneybadger.picker
+```
+the app can be launched directly in color picking mode using the command line
+option `--pick-color`. This could be perhaps be used to set up a keybinding.
+```
+flatpak run com.github.phoneybadger.picker --pick-color
+```
+and the program should also be visible in your launcher/application menu
+
 ## Building and running
 Download or clone the repo
 ```
@@ -48,7 +60,6 @@ the program should now be installed and can be run using
 ```
 flatpak run com.github.phoneybadger.trimmer
 ```
-it should also be visible in your launcher/application menu.
 
 ### Without flatpak
 

src/Application.vala

@@ -13,13 +13,21 @@ namespace Picker {
             {ACTION_START_PICK, action_start_pick}
         };
 
+        private const OptionEntry[] CMD_OPTION_ENTRIES = {
+            {"pick-color", 'p', OptionFlags.NONE, OptionArg.NONE, null, N_("Pick color"), null}
+        };
+
         public Application () {
             Object (
                 application_id: "com.github.phoneybadger.picker",
-                flags: ApplicationFlags.FLAGS_NONE
+                flags: ApplicationFlags.HANDLES_COMMAND_LINE
             );
         }
 
+        construct {
+            add_main_option_entries (CMD_OPTION_ENTRIES);
+        }
+
         public override void activate () {
             set_prefered_color_scheme ();
             add_action_entries (ACTION_ENTRIES, this);
@@ -37,6 +45,19 @@ namespace Picker {
             }
         }
 
+        public override int command_line (ApplicationCommandLine command) {
+            activate ();
+
+            /* Opens and immediately starts picking color if the --pick-color
+               flag is passed when launching from the command line. This could
+               be helpful for the user to set up keybindings and stuff */
+            var options = command.get_options_dict ();
+            if (options.contains ("pick-color")) {
+                lookup_action (ACTION_START_PICK).activate (null);
+            }
+            return 0;
+        }
+
         private void action_start_pick () {
             window.color_picker.start_picking ();
         }

src/Main.vala

@@ -4,7 +4,7 @@
  */
 public int main (string[] args) {
     var picker = new Picker.Application ();
-    int status = picker.run ();
+    int status = picker.run (args);
 
     return status;
 }