fix(overlay): handle X11 display scaling across monitors

- Convert X11 coordinates to Electron DIP per screen
- Relaunch unsupported Wayland sessions with the X11 Ozone backend

changes/x11-overlay-display-scaling.md

@@ -0,0 +1,4 @@
+type: fixed
+area: overlay
+
+- Fixed X11/XWayland overlays being oversized and offset from mpv under fractional or mixed-monitor display scaling.

docs-site/troubleshooting.md

@@ -405,8 +405,9 @@ On any Wayland session that is not Hyprland or Sway (KDE Plasma, GNOME, and othe
 
 SubMiner handles this automatically:
 
-- It launches its own window under XWayland (it sets `--ozone-platform-hint=x11`).
+- It launches its own window under XWayland (it sets `--ozone-platform=x11`).
 - Every mpv it launches (via the `subminer` launcher, Jellyfin, or YouTube) is pinned to XWayland too - Wayland environment hints are stripped and an X11 GPU context (`--gpu-context=x11vk,x11egl,x11`) is applied. Only the window context is overridden; your `vo`/`gpu-api` and user shaders are left alone.
+- Fractional and mixed-monitor display scaling is handled per screen when SubMiner maps XWayland mpv coordinates to the overlay.
 - While mpv is windowed, the overlay is a managed X11 window owned by the tracked mpv window (`WM_TRANSIENT_FOR`), so it stays above mpv while other foreground X11/Xwayland apps can still cover both windows.
 - While tracked mpv is fullscreen, SubMiner swaps the visible overlay to a focusable-false X11 override-redirect window. That path can stay above the active fullscreen mpv window without requiring a KDE/KWin-specific rule, and SubMiner hides/releases it when mpv is no longer the active X11/Xwayland window.
 - The visible overlay is shown inactive on Linux, so normal hover should not steal keyboard focus from mpv.

src/core/utils/electron-backend.test.ts

@@ -1,6 +1,6 @@
 import assert from 'node:assert/strict';
 import test from 'node:test';
-import { shouldForceX11ElectronBackend } from './electron-backend';
+import { resolveX11ElectronRelaunchArgs, shouldForceX11ElectronBackend } from './electron-backend';
 
 function withPlatform(platform: NodeJS.Platform, run: () => void): void {
   const original = Object.getOwnPropertyDescriptor(process, 'platform');
@@ -32,3 +32,70 @@ test('shouldForceX11ElectronBackend is false off Linux', () => {
     assert.equal(shouldForceX11ElectronBackend({}), false);
   });
 });
+
+test('resolveX11ElectronRelaunchArgs adds the raw X11 Ozone argument on unsupported Linux', () => {
+  assert.deepEqual(
+    resolveX11ElectronRelaunchArgs(
+      ['--start'],
+      {
+        DISPLAY: ':1',
+        WAYLAND_DISPLAY: 'wayland-0',
+        XDG_CURRENT_DESKTOP: 'KDE',
+      },
+      'linux',
+    ),
+    ['--start', '--ozone-platform=x11'],
+  );
+});
+
+test('resolveX11ElectronRelaunchArgs avoids loops and preserves native Wayland backends', () => {
+  const kdeWayland = {
+    DISPLAY: ':1',
+    WAYLAND_DISPLAY: 'wayland-0',
+    XDG_CURRENT_DESKTOP: 'KDE',
+  };
+  assert.equal(
+    resolveX11ElectronRelaunchArgs(['--start', '--ozone-platform=x11'], kdeWayland, 'linux'),
+    null,
+  );
+  assert.equal(
+    resolveX11ElectronRelaunchArgs(
+      ['--start'],
+      { ...kdeWayland, HYPRLAND_INSTANCE_SIGNATURE: 'hypr' },
+      'linux',
+    ),
+    null,
+  );
+  assert.equal(resolveX11ElectronRelaunchArgs(['--start'], kdeWayland, 'darwin'), null);
+  assert.equal(
+    resolveX11ElectronRelaunchArgs(
+      [],
+      {
+        ...kdeWayland,
+        SUBMINER_APP_ARGC: '1',
+        SUBMINER_APP_ARG_0: '--start',
+      },
+      'linux',
+    )?.at(-1),
+    '--ozone-platform=x11',
+  );
+  assert.equal(
+    resolveX11ElectronRelaunchArgs([], { ...kdeWayland, SUBMINER_X11_BOOTSTRAPPED: '1' }, 'linux'),
+    null,
+  );
+});
+
+test('resolveX11ElectronRelaunchArgs replaces an explicit unsupported Wayland argument', () => {
+  assert.deepEqual(
+    resolveX11ElectronRelaunchArgs(
+      ['--start', '--ozone-platform', 'wayland'],
+      {
+        DISPLAY: ':1',
+        WAYLAND_DISPLAY: 'wayland-0',
+        XDG_CURRENT_DESKTOP: 'KDE',
+      },
+      'linux',
+    ),
+    ['--start', '--ozone-platform=x11'],
+  );
+});

src/core/utils/electron-backend.ts

@@ -4,6 +4,9 @@ import { isSupportedWaylandCompositor } from '../../shared/mpv-x11-backend';
 
 const logger = createLogger('core:electron-backend');
 
+export const X11_ELECTRON_BOOTSTRAP_ENV = 'SUBMINER_X11_BOOTSTRAPPED';
+const X11_ELECTRON_OZONE_ARG = '--ozone-platform=x11';
+
 function getElectronOzonePlatformHint(env: NodeJS.ProcessEnv = process.env): string | null {
   const hint = env.ELECTRON_OZONE_PLATFORM_HINT?.trim().toLowerCase();
   if (hint) return hint;
@@ -24,11 +27,42 @@ function getElectronOzonePlatformHint(env: NodeJS.ProcessEnv = process.env): str
  * Electron Wayland backend is unsupported); the Hyprland/Sway case is left untouched so
  * {@link enforceUnsupportedWaylandMode} can report it.
  */
-export function shouldForceX11ElectronBackend(env: NodeJS.ProcessEnv = process.env): boolean {
-  if (process.platform !== 'linux') return false;
+export function shouldForceX11ElectronBackend(
+  env: NodeJS.ProcessEnv = process.env,
+  platform: NodeJS.Platform = process.platform,
+): boolean {
+  if (platform !== 'linux') return false;
   return !isSupportedWaylandCompositor(env);
 }
 
+export function resolveX11ElectronRelaunchArgs(
+  args: string[],
+  env: NodeJS.ProcessEnv = process.env,
+  platform: NodeJS.Platform = process.platform,
+): string[] | null {
+  if (!shouldForceX11ElectronBackend(env, platform)) return null;
+  if (env[X11_ELECTRON_BOOTSTRAP_ENV] === '1') return null;
+
+  const retainedArgs: string[] = [];
+  let alreadyForced = false;
+  for (let index = 0; index < args.length; index += 1) {
+    const arg = args[index];
+    if (arg === '--ozone-platform') {
+      const value = args[index + 1];
+      alreadyForced = value?.trim().toLowerCase() === 'x11';
+      if (value && !value.startsWith('--')) index += 1;
+      continue;
+    }
+    if (arg?.startsWith('--ozone-platform=')) {
+      alreadyForced = arg.slice('--ozone-platform='.length).trim().toLowerCase() === 'x11';
+      continue;
+    }
+    if (arg) retainedArgs.push(arg);
+  }
+
+  return alreadyForced ? null : [...retainedArgs, X11_ELECTRON_OZONE_ARG];
+}
+
 export function forceX11Backend(args: CliArgs): void {
   if (!shouldStartApp(args)) return;
   if (!shouldForceX11ElectronBackend()) return;

src/main-entry.ts

@@ -44,6 +44,10 @@ import {
   resolveDefaultLogFilePath,
   type LogRotation,
 } from './shared/log-files';
+import {
+  resolveX11ElectronRelaunchArgs,
+  X11_ELECTRON_BOOTSTRAP_ENV,
+} from './core/utils/electron-backend';
 
 const DEFAULT_TEXTHOOKER_PORT = 5174;
 
@@ -71,6 +75,22 @@ function applySanitizedEnv(sanitizedEnv: NodeJS.ProcessEnv): void {
   }
 }
 
+function spawnDetachedApp(childArgs: string[], env: NodeJS.ProcessEnv): void {
+  const keepalive = resolveAppImageMountKeepaliveInvocation(env);
+  const child = keepalive
+    ? spawn(keepalive.command, [...keepalive.args, ...childArgs], {
+        detached: true,
+        stdio: 'ignore',
+        env,
+      })
+    : spawn(process.execPath, childArgs, {
+        detached: true,
+        stdio: 'ignore',
+        env,
+      });
+  child.unref();
+}
+
 function resolveBundledWindowsMpvPluginEntrypoint(): string | undefined {
   return (
     resolvePackagedRuntimePluginPath({
@@ -296,26 +316,26 @@ async function runEntryProcess(): Promise<void> {
     return;
   }
 
+  const childArgs = hasTransportedStartupArgs(process.env) ? [] : process.argv.slice(1);
+  const x11ChildArgs = resolveX11ElectronRelaunchArgs(childArgs, process.env);
+
   if (shouldDetachBackgroundLaunch(process.argv, process.env)) {
-    const childArgs = hasTransportedStartupArgs(process.env) ? [] : process.argv.slice(1);
-    const keepalive = resolveAppImageMountKeepaliveInvocation(process.env);
-    const child = keepalive
-      ? spawn(keepalive.command, [...keepalive.args, ...childArgs], {
-          detached: true,
-          stdio: 'ignore',
-          env: sanitizeBackgroundEnv(process.env),
-        })
-      : spawn(process.execPath, childArgs, {
-          detached: true,
-          stdio: 'ignore',
-          env: sanitizeBackgroundEnv(process.env),
-        });
-    child.unref();
+    const childEnv = sanitizeBackgroundEnv(process.env);
+    if (x11ChildArgs) childEnv[X11_ELECTRON_BOOTSTRAP_ENV] = '1';
+    spawnDetachedApp(x11ChildArgs ?? childArgs, childEnv);
     // Let Electron stop bootstrap Chromium children before its AppImage mount is released.
     exitBackgroundBootstrap(app);
     return;
   }
 
+  if (x11ChildArgs) {
+    const childEnv = sanitizeStartupEnv(process.env);
+    childEnv[X11_ELECTRON_BOOTSTRAP_ENV] = '1';
+    spawnDetachedApp(x11ChildArgs, childEnv);
+    exitBackgroundBootstrap(app);
+    return;
+  }
+
   startMainProcess();
 }
 

src/main.ts

@@ -256,7 +256,6 @@ import {
 import {
   enforceUnsupportedWaylandMode,
   forceX11Backend,
-  shouldForceX11ElectronBackend,
   generateDefaultConfigFile,
   resolveConfiguredShortcuts,
   resolveKeybindings,
@@ -597,15 +596,6 @@ if (process.platform === 'linux') {
   );
   app.commandLine.appendSwitch('password-store', passwordStore);
   createLogger('main').debug(`Applied --password-store ${passwordStore}`);
-  // Pin the overlay to XWayland on unsupported Wayland sessions (everything except
-  // Hyprland/Sway). `setAlwaysOnTop`/`moveTop` are no-ops under a native Wayland surface,
-  // so the overlay can only stay above mpv under X11/XWayland. The command-line switch is
-  // applied at module load (before app init) so it reliably wins over the late env-var
-  // fallback in forceX11Backend().
-  if (shouldForceX11ElectronBackend(process.env)) {
-    app.commandLine.appendSwitch('ozone-platform-hint', 'x11');
-    createLogger('main').debug('Forced ozone-platform-hint=x11 for XWayland overlay stacking');
-  }
 }
 
 app.setName('SubMiner');

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');

src/window-trackers/index.ts

@@ -20,6 +20,7 @@ import { BaseWindowTracker } from './base-tracker';
 import { HyprlandWindowTracker } from './hyprland-tracker';
 import { SwayWindowTracker } from './sway-tracker';
 import { X11WindowTracker } from './x11-tracker';
+import type { ScreenToDipPoint } from './x11-tracker';
 import { MacOSWindowTracker } from './macos-tracker';
 import { WindowsWindowTracker } from './windows-tracker';
 import { createLogger } from '../logger';
@@ -51,6 +52,7 @@ function normalizeCompositor(value: string): Compositor | null {
 export function createWindowTracker(
   override?: string | null,
   targetMpvSocketPath?: string | null,
+  screenToDipPoint?: ScreenToDipPoint,
 ): BaseWindowTracker | null {
   let compositor = detectCompositor();
 
@@ -70,7 +72,11 @@ export function createWindowTracker(
     case 'sway':
       return new SwayWindowTracker(targetMpvSocketPath?.trim() || undefined);
     case 'x11':
-      return new X11WindowTracker(targetMpvSocketPath?.trim() || undefined);
+      return new X11WindowTracker(
+        targetMpvSocketPath?.trim() || undefined,
+        undefined,
+        screenToDipPoint,
+      );
     case 'macos':
       return new MacOSWindowTracker(targetMpvSocketPath?.trim() || undefined);
     case 'windows':

src/window-trackers/x11-tracker.test.ts

@@ -82,6 +82,47 @@ Height: 360`;
   });
 });
 
+test('X11WindowTracker converts both physical rectangle corners to Electron DIP', async () => {
+  const convertedPoints: Array<{ x: number; y: number }> = [];
+  const tracker = new X11WindowTracker(
+    undefined,
+    async (command, args) => {
+      if (command === 'xdotool' && args[0] === 'search') {
+        return '123';
+      }
+      if (command === 'xdotool' && args[0] === 'getactivewindow') {
+        return '123';
+      }
+      if (command === 'xwininfo') {
+        return `Absolute upper-left X:  2000
+Absolute upper-left Y:  125
+Width: 1000
+Height: 750`;
+      }
+      return '';
+    },
+    (point) => {
+      convertedPoints.push(point);
+      if (point.x === 2000) return { x: 1600, y: 100 };
+      return { x: 2400, y: 700 };
+    },
+  );
+
+  (tracker as unknown as { pollGeometry: () => void }).pollGeometry();
+  await new Promise((resolve) => setTimeout(resolve, 0));
+
+  assert.deepEqual(convertedPoints, [
+    { x: 2000, y: 125 },
+    { x: 3000, y: 875 },
+  ]);
+  assert.deepEqual(tracker.getGeometry(), {
+    x: 1600,
+    y: 100,
+    width: 800,
+    height: 600,
+  });
+});
+
 test('X11WindowTracker updates target focus from active X11 window', async () => {
   let activeWindowId = '999';
   const tracker = new X11WindowTracker(undefined, async (command, args) => {

src/window-trackers/x11-tracker.ts

@@ -20,6 +20,9 @@ import { execFile } from 'child_process';
 import { BaseWindowTracker } from './base-tracker';
 
 type CommandRunner = (command: string, args: string[]) => Promise<string>;
+export type ScreenToDipPoint = (point: { x: number; y: number }) => { x: number; y: number };
+
+const preservePoint: ScreenToDipPoint = (point) => point;
 
 function execFileUtf8(command: string, args: string[]): Promise<string> {
   return new Promise((resolve, reject) => {
@@ -87,16 +90,22 @@ export class X11WindowTracker extends BaseWindowTracker {
   private pollInterval: ReturnType<typeof setInterval> | null = null;
   private readonly targetMpvSocketPath: string | null;
   private readonly runCommand: CommandRunner;
+  private readonly screenToDipPoint: ScreenToDipPoint;
   private targetWindowId: string | null = null;
   private targetWindowPid: number | null = null;
   private pollInFlight = false;
   private currentPollIntervalMs = 750;
   private readonly stablePollIntervalMs = 250;
 
-  constructor(targetMpvSocketPath?: string, runCommand: CommandRunner = execFileUtf8) {
+  constructor(
+    targetMpvSocketPath?: string,
+    runCommand: CommandRunner = execFileUtf8,
+    screenToDipPoint: ScreenToDipPoint = preservePoint,
+  ) {
     super();
     this.targetMpvSocketPath = targetMpvSocketPath?.trim() || null;
     this.runCommand = runCommand;
+    this.screenToDipPoint = screenToDipPoint;
   }
 
   start(): void {
@@ -196,11 +205,25 @@ export class X11WindowTracker extends BaseWindowTracker {
     this.targetWindowPid = targetPid;
 
     const winInfo = await this.runCommand('xwininfo', ['-id', windowId]);
-    const geometry = parseX11WindowGeometry(winInfo);
-    if (!geometry) {
+    const physicalGeometry = parseX11WindowGeometry(winInfo);
+    if (!physicalGeometry) {
       this.updateGeometry(null);
       return;
     }
+    const topLeft = this.screenToDipPoint({
+      x: physicalGeometry.x,
+      y: physicalGeometry.y,
+    });
+    const bottomRight = this.screenToDipPoint({
+      x: physicalGeometry.x + physicalGeometry.width,
+      y: physicalGeometry.y + physicalGeometry.height,
+    });
+    const geometry = {
+      x: topLeft.x,
+      y: topLeft.y,
+      width: bottomRight.x - topLeft.x,
+      height: bottomRight.y - topLeft.y,
+    };
 
     const focused = await this.isWindowActive(windowId, targetPid);
     this.updateGeometry(geometry, focused);