layout improvements

src-tauri/src/lib.rs

@@ -677,12 +677,94 @@ fn specta_builder() -> Builder<tauri::Wry> {
 }
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
+/// Configure GStreamer (the media backend behind WebKitGTK's HTML5 `<video>`
+/// element on Linux) to prefer hardware-accelerated VAAPI decoding when the
+/// host provides it, falling back to software decoding otherwise.
+///
+/// All variables are only set if the user has not already exported them, so an
+/// explicit override (e.g. forcing software decode for debugging) is respected.
+/// They must be applied before WebKitGTK builds its GStreamer pipeline, hence the
+/// call at the very top of `run()`.
+#[cfg(target_os = "linux")]
+fn enable_linux_hardware_video_decoding() {
+    // Boost the rank of the modern stateless VAAPI decoders (gst-plugins-bad
+    // `va` plugin) so GStreamer selects them ahead of the software decoders. The
+    // `MAX` rank wins decoder autoplugging when the hardware/driver supports the
+    // codec; unsupported codecs simply fall through to software.
+    let rank_overrides = "vah264dec:MAX,vah265dec:MAX,vavp9dec:MAX,vaav1dec:MAX,\
+                          vampeg2dec:MAX,vavp8dec:MAX";
+
+    set_env_if_unset("GST_PLUGIN_FEATURE_RANK", rank_overrides);
+
+    // Ensure WebKit keeps GStreamer's hardware/DMABUF video path enabled. Setting
+    // this to "0" would force software decoding, so only default it to "1".
+    set_env_if_unset("WEBKIT_GST_ENABLE_HW_VIDEO_DECODER", "1");
+
+    info!("[INIT] Linux hardware video decoding (VAAPI) enabled where supported");
+
+    log_available_vaapi_decoders();
+}
+
+/// Probe (via `gst-inspect-1.0`, which ships with GStreamer) which VAAPI hardware
+/// video decoders GStreamer can actually load on this host, and log the result so
+/// it is clear at startup whether hardware decoding is genuinely available or
+/// whether playback will fall back to software.
+#[cfg(target_os = "linux")]
+fn log_available_vaapi_decoders() {
+    const HW_DECODERS: &[&str] = &[
+        "vah264dec", "vah265dec", "vavp9dec", "vaav1dec", "vampeg2dec", "vavp8dec",
+    ];
+
+    let available: Vec<&str> = HW_DECODERS
+        .iter()
+        .copied()
+        .filter(|name| {
+            std::process::Command::new("gst-inspect-1.0")
+                .arg(name)
+                .stdout(std::process::Stdio::null())
+                .stderr(std::process::Stdio::null())
+                .status()
+                .map(|s| s.success())
+                .unwrap_or(false)
+        })
+        .collect();
+
+    if available.is_empty() {
+        log::warn!(
+            "[INIT] No VAAPI hardware video decoders found via gst-inspect-1.0; \
+             video will use software decoding. Install the GStreamer 'va' plugin \
+             (gst-plugins-bad) and a VAAPI driver to enable hardware decoding."
+        );
+    } else {
+        info!(
+            "[INIT] VAAPI hardware video decoders available to GStreamer: {}",
+            available.join(", ")
+        );
+    }
+}
+
+#[cfg(target_os = "linux")]
+fn set_env_if_unset(key: &str, value: &str) {
+    if std::env::var_os(key).is_none() {
+        // SAFETY: called once at startup before any threads that read the
+        // environment (WebKitGTK/GStreamer) are spawned.
+        std::env::set_var(key, value);
+    }
+}
+
 pub fn run() {
     // Initialize logger
     env_logger::Builder::from_default_env()
         .filter_level(log::LevelFilter::Info)
         .init();
 
+    // On Linux, video plays through WebKitGTK's HTML5 <video> element, which uses
+    // GStreamer as its media backend. Enable hardware-accelerated (VAAPI) decoding
+    // when available so video transcoding/decoding does not fall back to the CPU.
+    // These must be set before WebKitGTK initializes its GStreamer pipeline.
+    #[cfg(target_os = "linux")]
+    enable_linux_hardware_video_decoding();
+
     // NOTE: TypeScript bindings are generated by the `export_typescript_bindings`
     // test (`cargo test export_typescript_bindings`), NOT at runtime. Calling
     // `.export()` here would try to write `../src/lib/api/bindings.ts` at app