[Windows]: Create dummy window to handle media control (#261)

Closes #259 

The code is from the example in Souvlaki repository: https://github.com/Sinono3/souvlaki/blob/master/examples/print_events.rs

spotify_player/Cargo.toml

@@ -47,6 +47,16 @@ regex = "1.9.5"
 daemonize = { version = "0.5.0", optional = true }
 ttl_cache = "0.5.1"
 
+[target.'cfg(target_os = "windows")'.dependencies.windows]
+version = "0.44"
+features = [
+	"Win32_Foundation",
+	"Win32_Graphics_Gdi",
+	"Win32_System_LibraryLoader",
+	"Win32_UI_WindowsAndMessaging"
+]
+optional = true
+
 [features]
 alsa-backend = ["streaming", "librespot-playback/alsa-backend"]
 pulseaudio-backend = ["streaming", "librespot-playback/pulseaudio-backend"]
@@ -58,7 +68,7 @@ sdl-backend = ["streaming", "librespot-playback/sdl-backend"]
 gstreamer-backend = ["streaming", "librespot-playback/gstreamer-backend"]
 streaming = ["librespot-playback", "librespot-connect"]
 lyric-finder = ["lyric_finder"]
-media-control = ["souvlaki", "winit"]
+media-control = ["souvlaki", "winit", "windows"]
 image = ["viuer", "dep:image"]
 sixel = ["image", "viuer/sixel"]
 notify = ["notify-rust"]

spotify_player/src/media_control.rs

@@ -57,7 +57,16 @@ pub fn start_event_watcher(
 ) -> Result<(), souvlaki::Error> {
     tracing::info!("Initializing application's media control event watcher...");
 
+    #[cfg(not(target_os = "windows"))]
     let hwnd = None;
+
+    #[cfg(target_os = "windows")]
+    let (hwnd, _dummy_window) = {
+        let dummy_window = windows::DummyWindow::new().unwrap();
+        let handle = Some(dummy_window.handle.0 as _);
+        (handle, dummy_window)
+    };
+
     let config = PlatformConfig {
         dbus_name: "spotify_player",
         display_name: "Spotify Player",
@@ -105,5 +114,117 @@ pub fn start_event_watcher(
     loop {
         update_control_metadata(&state, &mut controls, &mut track_info)?;
         std::thread::sleep(refresh_duration);
+
+        // this must be run repeatedly to ensure that
+        // the Windows event queue is processed by the app
+        #[cfg(target_os = "windows")]
+        windows::pump_event_queue();
+    }
+}
+
+// demonstrates how to make a minimal window to allow use of media keys on the command line
+// ref: https://github.com/Sinono3/souvlaki/blob/master/examples/print_events.rs
+#[cfg(target_os = "windows")]
+mod windows {
+    use std::io::Error;
+    use std::mem;
+
+    use windows::core::PCWSTR;
+    use windows::w;
+    use windows::Win32::Foundation::{HWND, LPARAM, LRESULT, WPARAM};
+    use windows::Win32::System::LibraryLoader::GetModuleHandleW;
+    use windows::Win32::UI::WindowsAndMessaging::{
+        CreateWindowExW, DefWindowProcW, DestroyWindow, DispatchMessageW, GetAncestor,
+        IsDialogMessageW, PeekMessageW, RegisterClassExW, TranslateMessage, GA_ROOT, MSG,
+        PM_REMOVE, WINDOW_EX_STYLE, WINDOW_STYLE, WM_QUIT, WNDCLASSEXW,
+    };
+
+    pub struct DummyWindow {
+        pub handle: HWND,
+    }
+
+    impl DummyWindow {
+        pub fn new() -> Result<DummyWindow, String> {
+            let class_name = w!("SimpleTray");
+
+            let handle_result = unsafe {
+                let instance = GetModuleHandleW(None)
+                    .map_err(|e| (format!("Getting module handle failed: {e}")))?;
+
+                let wnd_class = WNDCLASSEXW {
+                    cbSize: mem::size_of::<WNDCLASSEXW>() as u32,
+                    hInstance: instance,
+                    lpszClassName: class_name,
+                    lpfnWndProc: Some(Self::wnd_proc),
+                    ..Default::default()
+                };
+
+                if RegisterClassExW(&wnd_class) == 0 {
+                    return Err(format!(
+                        "Registering class failed: {}",
+                        Error::last_os_error()
+                    ));
+                }
+
+                let handle = CreateWindowExW(
+                    WINDOW_EX_STYLE::default(),
+                    class_name,
+                    w!(""),
+                    WINDOW_STYLE::default(),
+                    0,
+                    0,
+                    0,
+                    0,
+                    None,
+                    None,
+                    instance,
+                    None,
+                );
+
+                if handle.0 == 0 {
+                    Err(format!(
+                        "Message only window creation failed: {}",
+                        Error::last_os_error()
+                    ))
+                } else {
+                    Ok(handle)
+                }
+            };
+
+            handle_result.map(|handle| DummyWindow { handle })
+        }
+        extern "system" fn wnd_proc(
+            hwnd: HWND,
+            msg: u32,
+            wparam: WPARAM,
+            lparam: LPARAM,
+        ) -> LRESULT {
+            unsafe { DefWindowProcW(hwnd, msg, wparam, lparam) }
+        }
+    }
+
+    impl Drop for DummyWindow {
+        fn drop(&mut self) {
+            unsafe {
+                DestroyWindow(self.handle);
+            }
+        }
+    }
+
+    pub fn pump_event_queue() -> bool {
+        unsafe {
+            let mut msg: MSG = std::mem::zeroed();
+            let mut has_message = PeekMessageW(&mut msg, None, 0, 0, PM_REMOVE).as_bool();
+            while msg.message != WM_QUIT && has_message {
+                if !IsDialogMessageW(GetAncestor(msg.hwnd, GA_ROOT), &msg).as_bool() {
+                    TranslateMessage(&msg);
+                    DispatchMessageW(&msg);
+                }
+
+                has_message = PeekMessageW(&mut msg, None, 0, 0, PM_REMOVE).as_bool();
+            }
+
+            msg.message == WM_QUIT
+        }
     }
 }