Add playback speed control

For now we clamp the playback rate between 0.25x and 2.x, locked in 0.25x
offsets. Reverse playback or more fine-grained control could be added later on.

Fixes #76

data/net.baseart.Glide.ui

@@ -40,6 +40,19 @@
         <attribute name="label" translatable="yes">Video track</attribute>
       </submenu>
     </submenu>
+    <submenu id="playback-menu">
+      <attribute name="label" translatable="yes">Playback</attribute>
+      <section>
+        <item>
+          <attribute name="label" translatable="yes">Increase speed</attribute>
+          <attribute name="action">app.speed-increase</attribute>
+        </item>
+        <item>
+          <attribute name="label" translatable="yes">Decrease speed</attribute>
+          <attribute name="action">app.speed-decrease</attribute>
+        </item>
+      </section>
+    </submenu>
     <submenu id="subtitles-menu">
       <attribute name="label" translatable="yes">Subtitles</attribute>
       <section>
@@ -283,6 +296,19 @@ audio-volume-medium-symbolic</property>
                 <property name="title" translatable="yes">Mute the audio track</property>
               </object>
             </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="accelerator">Page_Up</property>
+                <property name="title" translatable="yes">Increase playback speed</property>
+              </object>
+            </child>
+            <child>
+              <object class="GtkShortcutsShortcut">
+                <property name="accelerator">Page_Down</property>
+                <property name="title" translatable="yes">Decrease playback speed</property>
+              </object>
+            </child>
+
           </object>
         </child>
         <child>

src/channel_player.rs

@@ -576,4 +576,24 @@ impl ChannelPlayer {
         self.gtksink
             .send_event(gst::event::Step::new(Buffers::ONE, 1.0, true, false));
     }
+
+    pub fn playback_rate(&self) -> f64 {
+        self.player.rate()
+    }
+
+    pub fn increase_speed(&self) {
+        let rate = self.player.rate();
+        let offset = 0.25;
+        if rate + offset <= 2.0 {
+            self.player.set_rate(rate + offset);
+        }
+    }
+
+    pub fn decrease_speed(&self) {
+        let rate = self.player.rate();
+        let offset = 0.25;
+        if rate > offset {
+            self.player.set_rate(rate - offset);
+        }
+    }
 }

src/main.rs

@@ -75,6 +75,8 @@ struct VideoPlayer {
     audio_offset_reset_action: gio::SimpleAction,
     subtitle_offset_reset_action: gio::SimpleAction,
     video_frame_step_action: gio::SimpleAction,
+    speed_increase_action: gio::SimpleAction,
+    speed_decrease_action: gio::SimpleAction,
     player_receiver: Option<glib::Receiver<PlayerEvent>>,
 }
 
@@ -177,6 +179,12 @@ impl VideoPlayer {
         let video_frame_step_action = gio::SimpleAction::new("video-frame-step", None);
         gtk_app.add_action(&video_frame_step_action);
 
+        let speed_increase_action = gio::SimpleAction::new("speed-increase", None);
+        gtk_app.add_action(&speed_increase_action);
+
+        let speed_decrease_action = gio::SimpleAction::new("speed-decrease", None);
+        gtk_app.add_action(&speed_decrease_action);
+
         let about = gio::SimpleAction::new("about", None);
         about.connect_activate(move |_, _| {
             with_video_player!(video_player {
@@ -248,6 +256,8 @@ impl VideoPlayer {
             audio_offset_reset_action,
             subtitle_offset_reset_action,
             video_frame_step_action,
+            speed_increase_action,
+            speed_decrease_action,
             player_receiver: Some(player_receiver),
         })
     }
@@ -471,6 +481,18 @@ impl VideoPlayer {
             })
         });
 
+        self.speed_decrease_action.connect_activate(|_, _| {
+            with_video_player!(video_player {
+                video_player.player.decrease_speed();
+            });
+        });
+
+        self.speed_increase_action.connect_activate(|_, _| {
+            with_video_player!(video_player {
+                video_player.player.increase_speed();
+            });
+        });
+
         let paintable = self.player.paintable();
         paintable.connect_invalidate_contents(|p| {
             with_video_player!(video_player {
@@ -542,11 +564,18 @@ impl VideoPlayer {
         self.ui_context.set_progress_bar_format_callback(|value| {
             let position = gst::ClockTime::from_seconds(value as u64);
             with_optional_video_player!(video_player {
-            if let Some(duration) = video_player.player.duration() {
-                format!("{position:.0} / {duration:.0}")
-            } else {
-                format!("{position:.0}")
-            }
+                let status = if let Some(duration) = video_player.player.duration() {
+                    format!("{position:.0} / {duration:.0}")
+                } else {
+                    format!("{position:.0}")
+                };
+                // FIXME: Ideally it'd be nice to show this on an OSD overlay?
+                let playback_rate = video_player.player.playback_rate();
+                if playback_rate != 1.0 {
+                    format!("{status} @ {playback_rate}.x")
+                } else {
+                    status
+                }
             } {
                 format!("{position:.0}")
             })

src/ui_context.rs

@@ -171,6 +171,8 @@ impl UIContext {
                 ("dump-pipeline", ["<Ctrl>d"]),
                 ("show-shortcuts", ["<Primary>question"]),
                 ("video-frame-step", ["<Primary>n"]),
+                ("speed-increase", ["Page_Up"]),
+                ("speed-decrease", ["Page_Down"]),
             ];
             for (action, accels) in accels_per_action.iter() {
                 app.set_accels_for_action(&format!("app.{action}"), accels);