[feat] add native Metal video rendering for Slint on macOS

src/gui/platform/metal_video_renderer.h

@@ -0,0 +1,100 @@
+#ifndef CROSSDESK_GUI_PLATFORM_METAL_VIDEO_RENDERER_H_
+#define CROSSDESK_GUI_PLATFORM_METAL_VIDEO_RENDERER_H_
+
+#include <cstddef>
+#include <cstdint>
+#include <memory>
+#include <string>
+#include <string_view>
+#include <vector>
+
+namespace crossdesk {
+
+// macOS video compositor used by CrossDesk only. MiniRTC continues to expose
+// tightly packed CPU NV12 frames; this renderer performs the single required
+// copy into shared Metal buffers and converts NV12 to RGB in the fragment
+// shader. AppKit attachment and rendering are main-thread operations, while
+// SubmitNv12() is safe to call from MiniRTC's decode callback thread.
+class MacMetalVideoRenderer {
+ public:
+  enum class SubmitResult {
+    submitted,
+    not_selected,
+    dropped,
+    failed,
+  };
+
+  enum class RenderResult {
+    rendered,
+    idle,
+    empty,
+    failed,
+  };
+
+  struct RenderOutcome {
+    RenderResult result = RenderResult::failed;
+    int width = 0;
+    int height = 0;
+    uint64_t sequence = 0;
+  };
+
+  MacMetalVideoRenderer();
+  ~MacMetalVideoRenderer();
+
+  MacMetalVideoRenderer(const MacMetalVideoRenderer&) = delete;
+  MacMetalVideoRenderer& operator=(const MacMetalVideoRenderer&) = delete;
+
+  bool IsReady() const;
+
+  // The selected stream is the only stream uploaded. Frames for background
+  // tabs are intentionally dropped to avoid wasting memory bandwidth.
+  bool SetSelectedStream(std::string remote_id);
+  void DiscardStream(std::string_view remote_id);
+
+  // Copies one tightly packed NV12 frame into a free shared Metal slot.
+  SubmitResult SubmitNv12(std::string_view remote_id, const uint8_t* data,
+                          size_t size, int width, int height);
+
+  // Seeds a newly selected stream from its retained CPU snapshot without
+  // replacing a newer decoded frame that is already queued or rendering.
+  SubmitResult SubmitCachedNv12(std::string_view remote_id,
+                                const uint8_t* data, size_t size, int width,
+                                int height);
+
+  // Attaches a native CAMetalLayer-backed sibling below Slint's NSView and
+  // restores the containing AppKit window's ordinary opaque titlebar.
+  // |slint_view| is an NSView* kept opaque so this header remains valid C++.
+  bool Attach(void* slint_view);
+  void Detach();
+  bool IsAttached() const;
+
+  // Cheap main-thread geometry check used by the UI frame timer. New decoded
+  // frames are tracked by GuiRuntime's dirty flag; this covers native resize,
+  // scale, stream selection, and retry work without a full session sync.
+  bool NeedsSurfaceRedraw() const;
+
+  // Draws the newest queued frame for |remote_id|. top_inset_points reserves
+  // Slint's tab strip above the native video surface. A rendered outcome
+  // carries metadata from the exact slot submitted to the command buffer.
+  RenderOutcome RenderLatest(std::string_view remote_id,
+                             double top_inset_points,
+                             bool native_titlebar_visible);
+
+  // Used only when a session closes, so thumbnail generation does not require
+  // a second per-frame CPU copy during normal playback.
+  bool CopyLatestNv12(std::string_view remote_id,
+                      std::vector<unsigned char>* output, int* width,
+                      int* height) const;
+
+ private:
+  SubmitResult SubmitNv12Internal(std::string_view remote_id,
+                                  const uint8_t* data, size_t size, int width,
+                                  int height, bool replace_pending);
+
+  struct Impl;
+  std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace crossdesk
+
+#endif  // CROSSDESK_GUI_PLATFORM_METAL_VIDEO_RENDERER_H_

src/gui/platform/window_drag.h

@@ -14,7 +14,14 @@ bool HideDisabledMainWindowZoomButton();
 
 // Configures live resize and replaces the stream window's native Space
 // fullscreen action with an immediate, single-window fullscreen transition.
-bool ConfigureStreamWindowLiveResize();
+// |slint_view| is the current stream window's AppKit NSView*. Passing the
+// identity explicitly prevents a closing window with the same title from
+// being selected during a later connection.
+bool ConfigureStreamWindowLiveResize(void* slint_view);
+
+// Drops the native stream-window reference if it belongs to |slint_view|.
+// This must run before the corresponding Slint component is destroyed.
+void UnregisterStreamWindow(void* slint_view);
 
 // Returns whether the configured stream window is currently the active AppKit
 // key window.

src/gui/platform/window_drag_mac.mm

@@ -17,7 +17,8 @@
 namespace crossdesk {
 namespace {
 
-NSWindow *stream_window = nil;
+__weak NSWindow *stream_window = nil;
+__weak NSView *stream_slint_view = nil;
 CrossDeskStreamFullscreenTarget *stream_fullscreen_target = nil;
 bool stream_fullscreen = false;
 NSRect stream_restore_frame = NSZeroRect;
@@ -101,48 +102,63 @@ bool HideDisabledMainWindowZoomButton() {
   }
 }
 
-bool ConfigureStreamWindowLiveResize() {
+bool ConfigureStreamWindowLiveResize(void *opaque_slint_view) {
   @autoreleasepool {
-    for (NSWindow *window in [NSApp windows]) {
-      if (![window.title isEqualToString:@"CrossDesk"]) {
-        continue;
-      }
-
-      NSButton *zoom_button =
-          [window standardWindowButton:NSWindowZoomButton];
-      // The stream window is resizable and therefore keeps an enabled native
-      // zoom button. The fixed-size main window's zoom button is disabled.
-      if (zoom_button == nil || !zoom_button.enabled) {
-        continue;
-      }
-
-      NSView *content_view = window.contentView;
-      if (content_view == nil) {
-        return false;
-      }
-
-      // During an ordinary edge resize, scale one cached frame and redraw once
-      // the new window size has settled.
-      window.preservesContentDuringLiveResize = YES;
-      content_view.layerContentsRedrawPolicy =
-          NSViewLayerContentsRedrawBeforeViewResize;
-      content_view.layerContentsPlacement =
-          NSViewLayerContentsPlacementScaleProportionallyToFit;
-      stream_window = window;
-      // Native Space fullscreen cross-fades an AppKit source snapshot over a
-      // separately rendered destination window. Disable that path for the
-      // stream window and route the green button to the immediate transition.
-      window.collectionBehavior =
-          (window.collectionBehavior &
-           ~(NSWindowCollectionBehaviorFullScreenPrimary |
-             NSWindowCollectionBehaviorFullScreenAuxiliary |
-             NSWindowCollectionBehaviorFullScreenAllowsTiling)) |
-          NSWindowCollectionBehaviorFullScreenNone;
-      InstallStreamFullscreenButton(window);
-      content_view.needsDisplay = YES;
-      return true;
+    NSView *slint_view = (__bridge NSView *)opaque_slint_view;
+    NSWindow *window = slint_view.window;
+    if (window == nil) {
+      return false;
     }
-    return false;
+
+    NSButton *zoom_button =
+        [window standardWindowButton:NSWindowZoomButton];
+    NSView *content_view = window.contentView;
+    if (zoom_button == nil || !zoom_button.enabled || content_view == nil) {
+      return false;
+    }
+
+    // During an ordinary edge resize, scale one cached frame and redraw once
+    // the new window size has settled.
+    window.preservesContentDuringLiveResize = YES;
+    content_view.layerContentsRedrawPolicy =
+        NSViewLayerContentsRedrawBeforeViewResize;
+    content_view.layerContentsPlacement =
+        NSViewLayerContentsPlacementScaleProportionallyToFit;
+    stream_window = window;
+    stream_slint_view = slint_view;
+    // Native Space fullscreen cross-fades an AppKit source snapshot over a
+    // separately rendered destination window. Disable that path for the
+    // stream window and route the green button to the immediate transition.
+    window.collectionBehavior =
+        (window.collectionBehavior &
+         ~(NSWindowCollectionBehaviorFullScreenPrimary |
+           NSWindowCollectionBehaviorFullScreenAuxiliary |
+           NSWindowCollectionBehaviorFullScreenAllowsTiling)) |
+        NSWindowCollectionBehaviorFullScreenNone;
+    InstallStreamFullscreenButton(window);
+    content_view.needsDisplay = YES;
+    return true;
+  }
+}
+
+void UnregisterStreamWindow(void *opaque_slint_view) {
+  @autoreleasepool {
+    NSView *slint_view = (__bridge NSView *)opaque_slint_view;
+    if (slint_view == nil || slint_view != stream_slint_view) {
+      return;
+    }
+    stream_window = nil;
+    stream_slint_view = nil;
+    stream_fullscreen = false;
+    stream_restore_frame = NSZeroRect;
+    stream_restore_style_mask = NSWindowStyleMaskTitled;
+    stream_restore_title_visibility = NSWindowTitleVisible;
+    stream_restore_titlebar_transparent = NO;
+    stream_restore_movable = YES;
+    stream_restore_close_hidden = NO;
+    stream_restore_miniaturize_hidden = NO;
+    stream_restore_zoom_hidden = NO;
+    stream_restore_presentation_options = NSApplicationPresentationDefault;
   }
 }