AudioApplet: Scrolling the Audio applet will adjust the main mix volume

The Audio applet now dislays the main mix volume next to the speaker
icon. A click on the applet still mutes the global mixer. By scrolling
the mouse wheel while on the applet, you can decrease/increase the mixer
volume. Different icons will be painted depending on the volume and the
mute state.

Happy listening :^)

MenuApplets/Audio/main.cpp

@@ -31,6 +31,7 @@
 #include <LibGUI/Window.h>
 #include <LibGfx/Bitmap.h>
 #include <LibGfx/Font.h>
+#include <LibGfx/Palette.h>
 
 class AudioWidget final : public GUI::Widget {
     C_OBJECT(AudioWidget)
@@ -44,8 +45,17 @@ public:
             m_audio_muted = muted;
             update();
         };
-        m_unmuted_bitmap = Gfx::Bitmap::load_from_file("/res/icons/audio-unmuted.png");
-        m_muted_bitmap = Gfx::Bitmap::load_from_file("/res/icons/audio-muted.png");
+
+        m_audio_client->on_main_mix_volume_change = [this](int volume) {
+            m_audio_volume = volume;
+            if (!m_audio_muted)
+                update();
+        };
+
+        m_volume_level_bitmaps.append({66, Gfx::Bitmap::load_from_file("/res/icons/audio-2.png")});
+        m_volume_level_bitmaps.append({33, Gfx::Bitmap::load_from_file("/res/icons/audio-1.png")});
+        m_volume_level_bitmaps.append({1,  Gfx::Bitmap::load_from_file("/res/icons/audio-0.png")});
+        m_volume_level_bitmaps.append({0,  Gfx::Bitmap::load_from_file("/res/icons/audio-muted.png")});
     }
 
     virtual ~AudioWidget() override {}
@@ -59,19 +69,49 @@ private:
         update();
     }
 
+    virtual void mousewheel_event(GUI::MouseEvent& event) override
+    {
+        if (m_audio_muted)
+            return;
+        int volume = clamp(m_audio_volume - event.wheel_delta() * 5, 0, 100);
+        m_audio_client->set_main_mix_volume(volume);
+        update();
+    }
+
     virtual void paint_event(GUI::PaintEvent& event) override
     {
         GUI::Painter painter(*this);
         painter.add_clip_rect(event.rect());
         painter.clear_rect(event.rect(), Color::from_rgba(0));
-        auto& audio_bitmap = m_audio_muted ? *m_muted_bitmap : *m_unmuted_bitmap;
+
+        auto& audio_bitmap = choose_bitmap_from_volume();
         painter.blit({}, audio_bitmap, audio_bitmap.rect());
+
+        auto volume_text = m_audio_muted ? "Mut" : String::format("%d%%", m_audio_volume);
+        painter.draw_text({16, 3, 24, 16}, volume_text, Gfx::Font::default_font(), Gfx::TextAlignment::TopLeft, palette().window_text());
     }
 
+    Gfx::Bitmap& choose_bitmap_from_volume()
+    {
+        if (m_audio_muted)
+            return *m_volume_level_bitmaps.last().bitmap;
+
+        for (auto& pair : m_volume_level_bitmaps) {
+            if (m_audio_volume >= pair.volume_threshold)
+                return *pair.bitmap;
+        }
+        ASSERT_NOT_REACHED();
+    }
+
+    struct VolumeBitmapPair {
+        int volume_threshold { 0 };
+        RefPtr<Gfx::Bitmap> bitmap;
+    };
+
     NonnullRefPtr<Audio::ClientConnection> m_audio_client;
-    RefPtr<Gfx::Bitmap> m_muted_bitmap;
-    RefPtr<Gfx::Bitmap> m_unmuted_bitmap;
+    Vector<VolumeBitmapPair, 4> m_volume_level_bitmaps;
     bool m_audio_muted { false };
+    int m_audio_volume { 100 };
 };
 
 int main(int argc, char** argv)
@@ -92,7 +132,7 @@ int main(int argc, char** argv)
     window->set_has_alpha_channel(true);
     window->set_title("Audio");
     window->set_window_type(GUI::WindowType::MenuApplet);
-    window->resize(12, 16);
+    window->resize(42, 16);
 
     window->set_main_widget<AudioWidget>();
     window->show();