Revert "general: Remove help-related code"

This reverts commit 2965799374.

Part-of: <https://gitlab.gnome.org/GNOME/Incubator/loupe/-/merge_requests/248>

data/gtk/window.ui

@@ -42,6 +42,10 @@
       </item>
     </section>
     <section>
+      <item>
+        <attribute name="label" translatable="yes">_Help</attribute>
+        <attribute name="action">app.help</attribute>
+      </item>
       <item>
         <attribute name="label" translatable="yes">_Keyboard Shortcuts</attribute>
         <attribute name="action">win.show-help-overlay</attribute>

help/C/index.page

@@ -0,0 +1,19 @@
+<page xmlns="http://projectmallard.org/1.0/"
+      type="guide" style="task"
+      xmlns:its="http://www.w3.org/2005/11/its"
+      id="index">
+
+  <info>
+    <desc>Help for Loupe.</desc>
+    <title type='link' role="trail"><media its:translate="no" type="image" src="figures/org.gnome.eog-symbolic.svg"/></title>
+    <title type='link'>Loupe</title>
+    <title type='text'>Loupe</title>
+    <credit type="author copyright">
+      <name>Christopher Davis</name>
+      <email>christopherdavis@gnome.org</email>
+      <years>2020</years>
+    </credit>
+  </info>
+
+<title>Loupe</title>
+</page>

help/meson.build

@@ -0,0 +1,8 @@
+sources = [
+  'index.page'
+]
+
+gnome.yelp(
+  meson.project_name(),
+  sources: sources,
+)

meson.build

@@ -53,6 +53,7 @@ conf.set('localedir', iv_localedir)
 conf.set('pkgdatadir', iv_pkgdatadir)
 
 subdir('data')
+subdir('help')
 subdir('src')
 subdir('po')
 

src/application.rs

@@ -20,9 +20,11 @@
 
 use crate::deps::*;
 use crate::util::gettext::*;
+use crate::util::spawn;
 
 use adw::prelude::*;
 use adw::subclass::prelude::*;
+use glib::clone;
 
 use crate::config;
 use crate::window::LpWindow;
@@ -112,6 +114,9 @@ impl LpApplication {
             gio::ActionEntryBuilder::new("about")
                 .activate(|app: &Self, _, _| app.show_about())
                 .build(),
+            gio::ActionEntryBuilder::new("help")
+                .activate(|app: &Self, _, _| app.show_help())
+                .build(),
             gio::ActionEntryBuilder::new("quit")
                 .activate(|app: &Self, _, _| app.quit())
                 .build(),
@@ -125,6 +130,7 @@ impl LpApplication {
 
         self.add_action_entries(actions);
 
+        self.set_accels_for_action("app.help", &["F1"]);
         self.set_accels_for_action("app.quit", &["<Ctrl>Q"]);
         self.set_accels_for_action("app.new-window", &["<Ctrl>N"]);
 
@@ -207,4 +213,16 @@ impl LpApplication {
 
         about.present();
     }
+
+    pub fn show_help(&self) {
+        spawn(clone!(@weak self as app => async move {
+            let context = app
+                .active_window()
+                .map(|w| gtk::prelude::WidgetExt::display(&w).app_launch_context());
+
+            if let Err(e) = gio::AppInfo::launch_default_for_uri_future("help:loupe", context.as_ref()).await {
+                log::error!("Failed to launch help: {}", e.message());
+            }
+        }));
+    }
 }