feat: support multiple Cursor windows in overlay

Renamed OverlayWindow to OverlayManager. Now discovers all on-screen
windows for the Cursor PID and creates/reuses/hides overlay windows
dynamically to match. Filters out tiny windows (<100px).
Verified: detects 3 windows across monitors.

Made-with: Cursor

scripts/test_overlay.py

@@ -5,13 +5,13 @@ import time
 from Cocoa import NSApplication, NSRunLoop, NSDate
 
 from cursor_flasher.config import Config
-from cursor_flasher.overlay import OverlayWindow
+from cursor_flasher.overlay import OverlayManager
 from cursor_flasher.detector import CursorDetector
 
 app = NSApplication.sharedApplication()
 
 config = Config()
-overlay = OverlayWindow(config)
+overlay = OverlayManager(config)
 detector = CursorDetector()
 
 pid = detector._find_cursor_pid()

src/cursor_flasher/overlay.py

@@ -12,7 +12,7 @@ from Cocoa import (
     NSTimer,
     NSScreen,
 )
-from Foundation import NSInsetRect, NSMakeRect
+from Foundation import NSInsetRect
 from Quartz import (
     CGWindowListCopyWindowInfo,
     kCGWindowListOptionOnScreenOnly,
@@ -20,6 +20,7 @@ from Quartz import (
     kCGWindowOwnerPID,
     kCGWindowBounds,
     kCGWindowLayer,
+    kCGWindowNumber,
 )
 
 from cursor_flasher.config import Config
@@ -67,63 +68,100 @@ class PulseBorderView(NSView):
         self.setNeedsDisplay_(True)
 
 
-class OverlayWindow:
-    """Manages the overlay window lifecycle."""
+class _OverlayEntry:
+    """A single overlay window + view pair."""
+    __slots__ = ("window", "view")
+
+    def __init__(self, window: NSWindow, view: PulseBorderView):
+        self.window = window
+        self.view = view
+
+
+class OverlayManager:
+    """Manages overlay windows for all Cursor windows belonging to a PID.
+
+    Creates one transparent overlay per Cursor window and keeps them
+    positioned and animated in sync.
+    """
 
     def __init__(self, config: Config):
         self._config = config
-        self._window: NSWindow | None = None
-        self._view: PulseBorderView | None = None
+        self._overlays: list[_OverlayEntry] = []
         self._timer: NSTimer | None = None
         self._phase = 0.0
         self._target_pid: int | None = None
 
     def show(self, pid: int) -> None:
-        """Show the pulsing overlay around the window belonging to `pid`."""
+        """Show pulsing overlays around every window belonging to `pid`."""
         self._target_pid = pid
-        frame = self._get_window_frame(pid)
-        if frame is None:
+        frames = self._get_all_window_frames(pid)
+        if not frames:
             return
 
-        if self._window is None:
-            self._create_window(frame)
-        else:
-            self._window.setFrame_display_(frame, True)
-            self._view.setFrame_(((0, 0), (frame[1][0], frame[1][1])))
+        self._sync_overlays(frames)
+
+        for entry in self._overlays:
+            entry.window.orderFrontRegardless()
 
-        self._window.orderFrontRegardless()
         self._start_animation()
 
     def hide(self) -> None:
-        """Hide and clean up the overlay."""
+        """Hide all overlay windows."""
         self._stop_animation()
-        if self._window is not None:
-            self._window.orderOut_(None)
+        for entry in self._overlays:
+            entry.window.orderOut_(None)
 
-    def update_position(self) -> None:
-        """Reposition overlay to match current Cursor window position."""
-        if self._target_pid is None or self._window is None:
+    def update_positions(self) -> None:
+        """Reposition overlays to track current Cursor window positions."""
+        if self._target_pid is None:
             return
-        frame = self._get_window_frame(self._target_pid)
-        if frame is not None:
-            self._window.setFrame_display_(frame, True)
-            self._view.setFrame_(((0, 0), (frame[1][0], frame[1][1])))
+        frames = self._get_all_window_frames(self._target_pid)
+        self._sync_overlays(frames)
 
-    def _create_window(self, frame) -> None:
-        self._window = NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(
+    def _sync_overlays(self, frames: list[tuple]) -> None:
+        """Ensure we have exactly len(frames) overlays, positioned correctly.
+
+        Reuses existing overlay windows where possible, creates new ones
+        if more windows appeared, and hides extras if windows closed.
+        """
+        needed = len(frames)
+        existing = len(self._overlays)
+
+        for i in range(needed):
+            frame = frames[i]
+            content_rect = ((0, 0), (frame[1][0], frame[1][1]))
+
+            if i < existing:
+                entry = self._overlays[i]
+                entry.window.setFrame_display_(frame, True)
+                entry.view.setFrame_(content_rect)
+            else:
+                entry = self._create_overlay(frame)
+                self._overlays.append(entry)
+                entry.window.orderFrontRegardless()
+
+        for i in range(needed, existing):
+            self._overlays[i].window.orderOut_(None)
+
+        if needed < existing:
+            self._overlays = self._overlays[:needed]
+
+    def _create_overlay(self, frame) -> _OverlayEntry:
+        window = NSWindow.alloc().initWithContentRect_styleMask_backing_defer_(
             frame, NSBorderlessWindowMask, 2, False  # NSBackingStoreBuffered
         )
-        self._window.setOpaque_(False)
-        self._window.setBackgroundColor_(NSColor.clearColor())
-        self._window.setLevel_(25)  # Above normal windows
-        self._window.setIgnoresMouseEvents_(True)
-        self._window.setHasShadow_(False)
+        window.setOpaque_(False)
+        window.setBackgroundColor_(NSColor.clearColor())
+        window.setLevel_(25)  # Above normal windows
+        window.setIgnoresMouseEvents_(True)
+        window.setHasShadow_(False)
 
         content_rect = ((0, 0), (frame[1][0], frame[1][1]))
-        self._view = PulseBorderView.alloc().initWithFrame_config_(
+        view = PulseBorderView.alloc().initWithFrame_config_(
             content_rect, self._config
         )
-        self._window.setContentView_(self._view)
+        window.setContentView_(view)
+        return _OverlayEntry(window, view)
 
     def _start_animation(self) -> None:
         if self._timer is not None:
@@ -144,22 +182,23 @@ class OverlayWindow:
         speed = self._config.pulse_speed
         step = (2.0 * math.pi) / (speed * 30.0)
         self._phase += step
-        if self._view is not None:
-            self._view.setPhase_(self._phase)
-        self.update_position()
+        for entry in self._overlays:
+            entry.view.setPhase_(self._phase)
+        self.update_positions()
 
     def _tick_(self, timer) -> None:
         self._tick_impl()
 
-    def _get_window_frame(self, pid: int):
-        """Get the screen frame of the main window for the given PID."""
+    def _get_all_window_frames(self, pid: int) -> list[tuple]:
+        """Get screen frames for all on-screen windows belonging to `pid`."""
         window_list = CGWindowListCopyWindowInfo(
             kCGWindowListOptionOnScreenOnly, kCGNullWindowID
         )
         if not window_list:
-            return None
+            return []
 
         screen_height = NSScreen.mainScreen().frame().size.height
+        frames = []
 
         for info in window_list:
             if info.get(kCGWindowOwnerPID) != pid:
@@ -169,10 +208,12 @@ class OverlayWindow:
             bounds = info.get(kCGWindowBounds)
             if bounds is None:
                 continue
-            x = bounds["X"]
-            y = screen_height - bounds["Y"] - bounds["Height"]
             w = bounds["Width"]
             h = bounds["Height"]
-            return ((x, y), (w, h))
+            if w < 100 or h < 100:
+                continue
+            x = bounds["X"]
+            y = screen_height - bounds["Y"] - h
+            frames.append(((x, y), (w, h)))
 
-        return None
+        return frames