Use native camera preview on supported platforms

apps/desktop/src-tauri/src/camera.rs

@@ -23,6 +23,7 @@ use tauri_plugin_store::Store;
 use tokio::sync::{broadcast, oneshot};
 use tracing::error;
 use wgpu::{CompositeAlphaMode, SurfaceTexture};
+use crate::general_settings::GeneralSettingsStore;
 
 static TOOLBAR_HEIGHT: f32 = 56.0; // also defined in Typescript
 
@@ -83,6 +84,22 @@ impl CameraPreview {
 
         let mut renderer = Renderer::init(window.clone()).await?;
 
+        // Update camera preview setting based on GPU composite alpha support
+        let supports_transparency = renderer.supports_transparency();
+        tracing::info!(
+            "GPU transparency support detected: {}, updating camera preview setting",
+            supports_transparency
+        );
+
+        if let Err(e) = GeneralSettingsStore::update_camera_preview_for_gpu_support(
+            &window.app_handle(),
+            supports_transparency
+        ) {
+            error!("Failed to update camera preview setting based on GPU support: {}", e);
+        } else {
+            tracing::info!("Successfully updated camera preview setting based on GPU capabilities");
+        }
+
         let store = self.store.clone();
         let mut reconfigure = self.reconfigure.1.resubscribe();
         let loading_state = self.loading.clone();
@@ -794,6 +811,14 @@ impl Renderer {
         self.queue.submit(Some(encoder.finish()));
         surface.present();
     }
+
+    /// Check if the renderer supports transparency via composite alpha modes
+    fn supports_transparency(&self) -> bool {
+        matches!(
+            self.surface_config.alpha_mode,
+            CompositeAlphaMode::PreMultiplied | CompositeAlphaMode::PostMultiplied
+        )
+    }
 }
 
 fn render_solid_frame(color: [u8; 4], width: u32, height: u32) -> (Vec<u8>, u32) {

apps/desktop/src-tauri/src/general_settings.rs

@@ -98,10 +98,10 @@ pub struct GeneralSettingsStore {
     pub post_deletion_behaviour: PostDeletionBehaviour,
 }
 
+// Initial default based on OS - this will be updated dynamically after GPU initialization
+// to reflect actual composite alpha mode support
 fn default_enable_native_camera_preview() -> bool {
-    // TODO:
-    // cfg!(target_os = "macos")
-    false
+    cfg!(any(target_os = "macos", target_os = "windows"))
 }
 
 fn default_enable_new_recording_flow() -> bool {
@@ -183,6 +183,21 @@ impl GeneralSettingsStore {
         }
     }
 
+    /// Update the native camera preview setting based on GPU composite alpha support.
+    ///
+    /// This method is called after GPU initialization to determine if the hardware
+    /// actually supports transparency via CompositeAlphaMode::PreMultiplied or
+    /// CompositeAlphaMode::PostMultiplied. The native camera preview requires
+    /// transparency support to render properly.
+    pub fn update_camera_preview_for_gpu_support(app: &AppHandle, supports_composite_alpha: bool) -> Result<(), String> {
+        // Only enable on macOS/Windows if GPU actually supports transparency
+        let should_enable = cfg!(any(target_os = "macos", target_os = "windows")) && supports_composite_alpha;
+
+        Self::update(app, |settings| {
+            settings.enable_native_camera_preview = should_enable;
+        })
+    }
+
     // i don't trust anyone to not overwrite the whole store lols
     pub fn update(app: &AppHandle, update: impl FnOnce(&mut Self)) -> Result<(), String> {
         let Ok(store) = app.store("store") else {