fix(overlay): handle X11 display scaling across monitors (#193)

src/main/runtime/linux-x11-cursor-point.test.ts

@@ -47,6 +47,29 @@ WINDOW=44040194
   assert.deepEqual(reader.getCursorScreenPoint({ x: 877, y: 718 }), { x: 1700, y: 1050 });
 });
 
+test('createLinuxX11CursorPointReader converts physical X11 coordinates to Electron DIP', async () => {
+  const convertedPoints: Array<{ x: number; y: number }> = [];
+  const reader = createLinuxX11CursorPointReader({
+    env: { DISPLAY: ':1' },
+    platform: 'linux',
+    runCommand: async () => `X=1424
+Y=697
+SCREEN=0
+WINDOW=44040194
+`,
+    screenToDipPoint: (point) => {
+      convertedPoints.push(point);
+      return { x: 1139, y: 557 };
+    },
+  });
+
+  reader.refresh();
+  await new Promise((resolve) => setImmediate(resolve));
+
+  assert.deepEqual(reader.getCursorScreenPoint({ x: 0, y: 0 }), { x: 1139, y: 557 });
+  assert.deepEqual(convertedPoints, [{ x: 1424, y: 697 }]);
+});
+
 test('createLinuxX11CursorPointReader does not spawn off X11 Linux', () => {
   const calls: string[] = [];
   const reader = createLinuxX11CursorPointReader({

src/main/runtime/linux-x11-cursor-point.ts

@@ -36,11 +36,13 @@ export function createLinuxX11CursorPointReader(options?: {
   now?: () => number;
   platform?: NodeJS.Platform;
   runCommand?: CommandRunner;
+  screenToDipPoint?: (point: PointerPoint) => PointerPoint;
 }) {
   const env = options?.env ?? process.env;
   const now = options?.now ?? (() => Date.now());
   const platform = options?.platform ?? process.platform;
   const runCommand = options?.runCommand ?? execFileUtf8;
+  const screenToDipPoint = options?.screenToDipPoint ?? ((point: PointerPoint) => point);
   let latest: { point: PointerPoint; updatedAtMs: number } | null = null;
   let inFlight = false;
   let retryAfterMs = 0;
@@ -63,7 +65,7 @@ export function createLinuxX11CursorPointReader(options?: {
           retryAfterMs = now() + COMMAND_FAILURE_RETRY_DELAY_MS;
           return;
         }
-        latest = { point, updatedAtMs: now() };
+        latest = { point: screenToDipPoint(point), updatedAtMs: now() };
         retryAfterMs = 0;
       })
       .catch(() => {

src/main/runtime/visible-overlay-interaction-runtime.ts

@@ -289,7 +289,9 @@ export function createVisibleOverlayInteractionRuntime(deps: VisibleOverlayInter
     if (initialArgs && isHeadlessInitialCommand(initialArgs)) {
       return null;
     }
-    return createWindowTrackerCore(override, targetMpvSocketPath);
+    return createWindowTrackerCore(override, targetMpvSocketPath, (point) =>
+      screen.screenToDipPoint(point),
+    );
   }
 
   function bindVisibleOverlayOwner(): void {
@@ -627,7 +629,9 @@ export function createVisibleOverlayInteractionRuntime(deps: VisibleOverlayInter
 
   ensureWindowsVisibleOverlayForegroundPollLoop();
 
-  const linuxX11CursorPointReader = createLinuxX11CursorPointReader();
+  const linuxX11CursorPointReader = createLinuxX11CursorPointReader({
+    screenToDipPoint: (point) => screen.screenToDipPoint(point),
+  });
 
   function getLinuxOverlayPointerMeasurement() {
     const measurement = overlayContentMeasurementStore.getLatestByLayer('visible');