fix(capture): build the macOS helper again, and own the cover's promise in its thread

PickerSession's static desktopIconWindowIDs shadowed the OpenScreenCaptureCore function it called, so the helper did not compile. The Windows cover captured a local std::promise by reference that show() could destroy while set_value was still running.

Author: EtienneLescot

electron/native/screencapturekit/Sources/OpenScreenScreenCaptureKitHelper/PickerSession.swift

@@ -96,7 +96,7 @@ final class PickerSession: NSObject, SCContentSharingPickerObserver, @unchecked
 		// the HUD and the notes window belong to Electron. Measured: a window owned by the
 		// parent app shows in the capture unless it is listed here.
 		configuration.excludedWindowIDs =
-			excludedWindowIDs + Self.desktopIconWindowIDs(hideDesktopIcons: hideDesktopIcons)
+			excludedWindowIDs + Self.finderDesktopIconWindowIDs(hideDesktopIcons: hideDesktopIcons)
 		// By app, not by window: a banner is a window created after the pick, so no id
 		// list taken now could name it.
 		configuration.excludedBundleIDs = [notificationCenterBundleID]
@@ -174,7 +174,9 @@ final class PickerSession: NSObject, SCContentSharingPickerObserver, @unchecked
 	/// need the Screen Recording grant the picker exists to avoid. Owner and level are
 	/// readable without it. The icons stay put for the whole session, so ids taken at pick
 	/// time hold -- unless Finder relaunches, which gives them new ones.
-	private static func desktopIconWindowIDs(hideDesktopIcons: Bool) -> [Int] {
+	/// Not named `desktopIconWindowIDs`: inside this class that name would shadow the
+	/// OpenScreenCaptureCore function it calls.
+	private static func finderDesktopIconWindowIDs(hideDesktopIcons: Bool) -> [Int] {
 		guard hideDesktopIcons,
 			let entries = CGWindowListCopyWindowInfo([.optionOnScreenOnly], kCGNullWindowID)
 				as? [[String: Any]]
@@ -193,7 +195,7 @@ final class PickerSession: NSObject, SCContentSharingPickerObserver, @unchecked
 				layer: entry[kCGWindowLayer as String] as? Int ?? 0
 			)
 		}
-		return desktopIconWindowIDs(candidates).map { Int($0) }
+		return OpenScreenCaptureCore.desktopIconWindowIDs(candidates).map { Int($0) }
 	}
 
 	private static func display(containing frame: CGRect) -> CGDirectDisplayID? {

electron/native/wgc-capture/src/desktop_icon_cover.cpp

@@ -62,9 +62,11 @@ bool DesktopIconCover::show(HMONITOR monitor) {
         return false;
     }
 
-    std::promise<bool> placed;
-    std::future<bool> placedResult = placed.get_future();
-    thread_ = std::thread([this, rect = info.rcMonitor, &placed]() {
+    // Moved into the thread, not captured by reference: `get()` can return before
+    // `set_value` has finished with the promise, and this frame is gone by then.
+    std::promise<bool> promise;
+    std::future<bool> placedResult = promise.get_future();
+    thread_ = std::thread([this, rect = info.rcMonitor, placed = std::move(promise)]() mutable {
         threadId_ = GetCurrentThreadId();
         HINSTANCE instance = GetModuleHandleW(nullptr);
         WNDCLASSEXW windowClass{sizeof(windowClass)};