Fix Windows overlay scaling bounds

changes/fix-windows-overlay-scaling.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- Fixed Windows overlay window tracking on scaled displays by converting native tracked window bounds to Electron DIP coordinates before applying overlay bounds.

src/core/services/overlay-window-bounds.test.ts

@@ -0,0 +1,36 @@
+import assert from 'node:assert/strict';
+import test from 'node:test';
+import { normalizeOverlayWindowBoundsForPlatform } from './overlay-window-bounds';
+
+test('normalizeOverlayWindowBoundsForPlatform returns original geometry outside Windows', () => {
+  const geometry = { x: 150, y: 90, width: 1200, height: 675 };
+  assert.deepEqual(normalizeOverlayWindowBoundsForPlatform(geometry, 'linux', null), geometry);
+});
+
+test('normalizeOverlayWindowBoundsForPlatform converts Windows physical pixels to DIP', () => {
+  assert.deepEqual(
+    normalizeOverlayWindowBoundsForPlatform(
+      {
+        x: 150,
+        y: 75,
+        width: 1920,
+        height: 1080,
+      },
+      'win32',
+      {
+        screenToDipRect: (_window, rect) => ({
+          x: Math.round(rect.x / 1.5),
+          y: Math.round(rect.y / 1.5),
+          width: Math.round(rect.width / 1.5),
+          height: Math.round(rect.height / 1.5),
+        }),
+      },
+    ),
+    {
+      x: 100,
+      y: 50,
+      width: 1280,
+      height: 720,
+    },
+  );
+});

src/core/services/overlay-window-bounds.ts

@@ -0,0 +1,25 @@
+import type { WindowGeometry } from '../../types';
+
+type ScreenDipConverter = {
+  screenToDipRect: (
+    window: Electron.BrowserWindow | null,
+    rect: Electron.Rectangle,
+  ) => Electron.Rectangle;
+};
+
+export function normalizeOverlayWindowBoundsForPlatform(
+  geometry: WindowGeometry,
+  platform: NodeJS.Platform,
+  screen: ScreenDipConverter | null,
+): WindowGeometry {
+  if (platform !== 'win32' || !screen) {
+    return geometry;
+  }
+
+  return screen.screenToDipRect(null, {
+    x: geometry.x,
+    y: geometry.y,
+    width: geometry.width,
+    height: geometry.height,
+  });
+}

src/core/services/overlay-window.ts

@@ -1,4 +1,4 @@
-import { BrowserWindow, type Session } from 'electron';
+import { BrowserWindow, screen, type Session } from 'electron';
 import * as path from 'path';
 import { WindowGeometry } from '../../types';
 import { createLogger } from '../../logger';
@@ -8,6 +8,7 @@ import {
   type OverlayWindowKind,
 } from './overlay-window-input';
 import { buildOverlayWindowOptions } from './overlay-window-options';
+import { normalizeOverlayWindowBoundsForPlatform } from './overlay-window-bounds';
 
 const logger = createLogger('main:overlay-window');
 const overlayWindowLayerByInstance = new WeakMap<BrowserWindow, OverlayWindowKind>();
@@ -33,12 +34,7 @@ export function updateOverlayWindowBounds(
   window: BrowserWindow | null,
 ): void {
   if (!geometry || !window || window.isDestroyed()) return;
-  window.setBounds({
+  window.setBounds(normalizeOverlayWindowBoundsForPlatform(geometry, process.platform, screen));
-    x: geometry.x,
-    y: geometry.y,
-    width: geometry.width,
-    height: geometry.height,
-  });
 }
 
 export function ensureOverlayWindowLevel(window: BrowserWindow): void {