Improve screencast performance: lower defaults, fps cap, drop mousemove flood

Co-authored-by: Cursor <cursoragent@cursor.com>

app/browser_manager.py

@@ -7,7 +7,13 @@ from typing import Any, Optional
 
 from playwright.async_api import Browser, BrowserContext, Page, Playwright, async_playwright
 
-from app.security import get_idle_timeout, get_screencast_quality, get_viewport_size
+from app.security import (
+    get_idle_timeout,
+    get_screencast_max_fps,
+    get_screencast_nth_frame,
+    get_screencast_quality,
+    get_viewport_size,
+)
 
 
 @dataclass
@@ -25,8 +31,9 @@ class BrowserSession:
     screencast_task: Optional[asyncio.Task] = None
     idle_task: Optional[asyncio.Task] = None
     closed: bool = False
-    viewport_width: int = 1280
-    viewport_height: int = 720
+    viewport_width: int = 1024
+    viewport_height: int = 576
+    last_frame_sent_at: float = 0.0
 
 
 class BrowserManager:
@@ -53,7 +60,6 @@ class BrowserManager:
                     "--no-sandbox",
                     "--disable-setuid-sandbox",
                     "--disable-dev-shm-usage",
-                    "--disable-gpu",
                 ],
             )
             context = await browser.new_context(
@@ -143,7 +149,7 @@ class BrowserManager:
         return session.url
 
     def subscribe(self, session: BrowserSession) -> asyncio.Queue:
-        queue: asyncio.Queue = asyncio.Queue(maxsize=8)
+        queue: asyncio.Queue = asyncio.Queue(maxsize=2)
         session.subscribers.add(queue)
         return queue
 
@@ -173,10 +179,13 @@ class BrowserManager:
         await self._broadcast(session, {"type": "url_update", "url": session.url})
 
     async def _run_screencast(self, session: BrowserSession, quality: int) -> None:
+        nth_frame = get_screencast_nth_frame()
+        min_frame_interval = 1.0 / get_screencast_max_fps()
+
         async def on_screencast_frame(params: dict) -> None:
             if session.closed:
                 return
-            data = params.get("data", "")
+
             session_id = params.get("sessionId")
             try:
                 await session.cdp.send(
@@ -184,10 +193,18 @@ class BrowserManager:
                 )
             except Exception:
                 return
+
+            now = time.time()
+            if now - session.last_frame_sent_at < min_frame_interval:
+                return
+
+            data = params.get("data", "")
             try:
                 frame_bytes = base64.b64decode(data)
             except Exception:
                 return
+
+            session.last_frame_sent_at = now
             await self._broadcast(
                 session,
                 {
@@ -211,7 +228,7 @@ class BrowserManager:
                 "quality": quality,
                 "maxWidth": session.viewport_width,
                 "maxHeight": session.viewport_height,
-                "everyNthFrame": 1,
+                "everyNthFrame": nth_frame,
             },
         )
 

app/input_handler.py

@@ -29,9 +29,6 @@ async def handle_input(
         return {"type": "ack", "action": action}
 
     if action == "mousemove":
-        x = float(payload.get("x", 0))
-        y = float(payload.get("y", 0))
-        await page.mouse.move(x, y)
         return None
 
     if action == "wheel":

app/security.py

@@ -83,11 +83,19 @@ def get_idle_timeout() -> int:
 
 
 def get_viewport_size() -> tuple[int, int]:
-    width = max(800, int(os.getenv("VIEWPORT_WIDTH", "1280")))
-    height = max(600, int(os.getenv("VIEWPORT_HEIGHT", "720")))
+    width = max(800, int(os.getenv("VIEWPORT_WIDTH", "1024")))
+    height = max(600, int(os.getenv("VIEWPORT_HEIGHT", "576")))
     return width, height
 
 
 def get_screencast_quality() -> int:
-    quality = int(os.getenv("SCREENCAST_QUALITY", "80"))
+    quality = int(os.getenv("SCREENCAST_QUALITY", "55"))
     return min(100, max(10, quality))
+
+
+def get_screencast_nth_frame() -> int:
+    return max(1, int(os.getenv("SCREENCAST_EVERY_NTH_FRAME", "2")))
+
+
+def get_screencast_max_fps() -> int:
+    return min(30, max(5, int(os.getenv("SCREENCAST_MAX_FPS", "15"))))