fix(overlay): prevent Windows mouse lag during click-through tracking (#201)

src/core/services/ipc.ts

@@ -34,6 +34,7 @@ import {
   parseSubsyncManualRunRequest,
   parseYoutubePickerResolveRequest,
 } from '../../shared/ipc/validators';
+import { applyOverlayClickThrough } from './overlay-click-through';
 
 const { ipcMain } = electron;
 
@@ -442,7 +443,13 @@ export function registerIpcHandlers(deps: IpcServiceDeps, ipc: IpcMainRegistrar
       const senderWindow =
         electron.BrowserWindow?.fromWebContents((event as IpcMainEvent).sender) ?? null;
       if (senderWindow && !senderWindow.isDestroyed()) {
-        senderWindow.setIgnoreMouseEvents(ignore, parsedOptions);
+        // Route forwarding requests through the platform-aware helper so Windows never
+        // installs Electron's global mouse hook (see overlay-click-through.ts).
+        if (ignore && parsedOptions?.forward) {
+          applyOverlayClickThrough(senderWindow);
+        } else {
+          senderWindow.setIgnoreMouseEvents(ignore, parsedOptions);
+        }
       }
       deps.onOverlayMouseInteractionChanged?.(!ignore, senderWindow);
     },

src/core/services/overlay-click-through.test.ts

@@ -0,0 +1,21 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+
+import { applyOverlayClickThrough } from './overlay-click-through';
+
+test('applyOverlayClickThrough requests forwarding only off Windows', () => {
+  const calls: Array<{ ignore: boolean; forward: boolean }> = [];
+  const window = {
+    setIgnoreMouseEvents: (ignore: boolean, options?: { forward?: boolean }) => {
+      calls.push({ ignore, forward: options?.forward === true });
+    },
+  };
+
+  applyOverlayClickThrough(window, true);
+  applyOverlayClickThrough(window, false);
+
+  assert.deepEqual(calls, [
+    { ignore: true, forward: false },
+    { ignore: true, forward: true },
+  ]);
+});

src/core/services/overlay-click-through.ts

@@ -0,0 +1,27 @@
+type ClickThroughWindow = {
+  setIgnoreMouseEvents: (ignore: boolean, options?: { forward?: boolean }) => void;
+};
+
+/**
+ * Puts an overlay window into click-through mode. Forwarded mouse-move ({ forward: true }) is
+ * what lets renderer hover tracking wake a click-through overlay, but on Windows Electron
+ * implements it with a global WH_MOUSE_LL hook whose callback runs on the main-process message
+ * loop, so any main-thread stall delays mouse input system-wide (electron/electron#10183).
+ * Windows instead wakes the overlay via the main-process cursor poll
+ * (tickWindowsOverlayPointerInteraction), so no forwarding is requested there. macOS still
+ * needs forwarding for renderer hover tracking; Linux ignores the flag entirely
+ * (electron/electron#16777).
+ *
+ * Pass isWindowsPlatform when the caller already carries a platform flag (tests simulate
+ * platforms through it); otherwise the real process.platform decides.
+ */
+export function applyOverlayClickThrough(
+  window: ClickThroughWindow,
+  isWindowsPlatform?: boolean,
+): void {
+  if (isWindowsPlatform ?? process.platform === 'win32') {
+    window.setIgnoreMouseEvents(true);
+  } else {
+    window.setIgnoreMouseEvents(true, { forward: true });
+  }
+}

src/core/services/overlay-visibility.test.ts

@@ -848,7 +848,7 @@ test('Windows visible overlay stays click-through and binds to mpv while tracked
   } as never);
 
   assert.ok(calls.includes('opacity:0'));
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('show-inactive'));
   assert.ok(calls.includes('sync-windows-z-order'));
   assert.ok(!calls.includes('move-top'));
@@ -1060,7 +1060,7 @@ test('tracked Windows overlay refresh rebinds while already visible', () => {
     isWindowsPlatform: true,
   } as never);
 
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('sync-windows-z-order'));
   assert.ok(!calls.includes('move-top'));
   assert.ok(!calls.includes('show'));
@@ -1134,7 +1134,7 @@ test('forced passthrough still reapplies while visible on Windows', () => {
     forceMousePassthrough: true,
   } as never);
 
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(!calls.includes('always-on-top:false'));
   assert.ok(!calls.includes('move-top'));
   assert.ok(calls.includes('sync-windows-z-order'));
@@ -1339,7 +1339,7 @@ test('tracked Windows overlay rebinds without hiding when tracker focus changes'
 
   assert.ok(!calls.includes('always-on-top:false'));
   assert.ok(!calls.includes('move-top'));
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('sync-windows-z-order'));
   assert.ok(!calls.includes('ensure-level'));
   assert.ok(!calls.includes('enforce-order'));
@@ -1489,7 +1489,7 @@ test('tracked Windows overlay reshows click-through even if focus state is stale
     isWindowsPlatform: true,
   } as never);
 
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('show-inactive'));
   assert.ok(!calls.includes('show'));
 });
@@ -1532,7 +1532,7 @@ test('tracked Windows overlay binds above mpv even when tracker focus lags', ()
 
   assert.ok(!calls.includes('always-on-top:false'));
   assert.ok(!calls.includes('move-top'));
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('sync-windows-z-order'));
   assert.ok(!calls.includes('ensure-level'));
 });
@@ -2193,7 +2193,7 @@ test('Windows preserves visible overlay and rebinds to mpv while tracker transie
   assert.ok(!calls.includes('show'));
   assert.ok(!calls.includes('always-on-top:false'));
   assert.ok(!calls.includes('move-top'));
-  assert.ok(calls.includes('mouse-ignore:true:forward'));
+  assert.ok(calls.includes('mouse-ignore:true:plain'));
   assert.ok(calls.includes('sync-windows-z-order'));
   assert.ok(!calls.includes('ensure-level'));
   assert.ok(calls.includes('sync-shortcuts'));

src/core/services/overlay-visibility.ts

@@ -1,6 +1,7 @@
 import type { BrowserWindow } from 'electron';
 import { BaseWindowTracker } from '../../window-trackers';
 import { WindowGeometry } from '../../types';
+import { applyOverlayClickThrough } from './overlay-click-through';
 import { OVERLAY_WINDOW_CONTENT_READY_FLAG } from './overlay-window-flags';
 
 const WINDOWS_OVERLAY_REVEAL_DELAY_MS = 48;
@@ -117,7 +118,7 @@ export function updateVisibleOverlayVisibility(args: {
       clearPendingWindowsOverlayReveal(mainWindow);
       setOverlayWindowOpacity(mainWindow, 0);
     }
-    mainWindow.setIgnoreMouseEvents(true, { forward: true });
+    applyOverlayClickThrough(mainWindow, args.isWindowsPlatform);
     releaseOverlayWindowLevel(mainWindow);
     mainWindow.hide();
     args.syncOverlayShortcuts();
@@ -215,7 +216,7 @@ export function updateVisibleOverlayVisibility(args: {
       shouldPreserveWindowsOverlayDuringFocusHandoff ||
       (hasWindowsForegroundProcessSignal && windowsForegroundProcessName === 'mpv');
     if (shouldIgnoreMouseEvents) {
-      mainWindow.setIgnoreMouseEvents(true, { forward: true });
+      applyOverlayClickThrough(mainWindow, args.isWindowsPlatform);
     } else {
       mainWindow.setIgnoreMouseEvents(false);
     }
@@ -263,7 +264,7 @@ export function updateVisibleOverlayVisibility(args: {
         if (hasNonNativeInputRegion) {
           mainWindow.setIgnoreMouseEvents(false);
         } else {
-          mainWindow.setIgnoreMouseEvents(true, { forward: true });
+          applyOverlayClickThrough(mainWindow, args.isWindowsPlatform);
         }
         if (args.isWindowsPlatform) {
           scheduleWindowsOverlayReveal(
@@ -424,7 +425,7 @@ export function updateVisibleOverlayVisibility(args: {
       return;
     }
     args.setTrackerNotReadyWarningShown(false);
-    mainWindow.setIgnoreMouseEvents(true, { forward: true });
+    applyOverlayClickThrough(mainWindow, args.isWindowsPlatform);
     releaseOverlayWindowLevel(mainWindow);
     mainWindow.hide();
     args.syncOverlayShortcuts();