raise screen share quality and stop the grid from overflowing

Screen share was capped by WebRTC's default ~2.5 Mbps and by window
capture resolution, and fixed aspect-video cards forced the page to
scroll. Adds minimal [sejong-rtc] logs to diagnose ICE failures.

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

composables/useScreenShare.ts

@@ -1,7 +1,10 @@
+import { rtcLog, rtcWarn } from '~/utils/rtcLog'
+
 export function useScreenShare() {
   const localStream = ref<MediaStream | null>(null)
   const streamId = ref<string | null>(null)
   const error = ref<string | null>(null)
+  const settings = ref<MediaTrackSettings | null>(null)
   const isSharing = computed(() => Boolean(localStream.value))
 
   async function startShare(clientId: string) {
@@ -9,11 +12,12 @@ export function useScreenShare() {
     try {
       const stream = await navigator.mediaDevices.getDisplayMedia({
         video: {
-          width: { ideal: 1920 },
-          height: { ideal: 1080 },
+          width: { ideal: 1920, max: 1920 },
+          height: { ideal: 1080, max: 1080 },
           frameRate: { ideal: 60, max: 60 },
+          // Monitor capture reaches full 1080p; window capture is capped by the window size.
           // @ts-expect-error displaySurface is supported in Chromium
-          displaySurface: 'window',
+          displaySurface: 'monitor',
         },
         audio: {
           // @ts-expect-error Chromium system audio options
@@ -27,9 +31,30 @@ export function useScreenShare() {
       streamId.value = `${clientId}-${Date.now()}`
 
       const videoTrack = stream.getVideoTracks()[0]
-      videoTrack?.addEventListener('ended', () => {
-        stopShare()
-      })
+      if (videoTrack) {
+        // Games favour framerate over per-frame sharpness.
+        videoTrack.contentHint = 'motion'
+        try {
+          await videoTrack.applyConstraints({
+            width: { ideal: 1920 },
+            height: { ideal: 1080 },
+            frameRate: { ideal: 60 },
+          })
+        } catch (e) {
+          rtcWarn('applyConstraints failed', String(e))
+        }
+        settings.value = videoTrack.getSettings()
+        rtcLog('capture:settings', settings.value)
+        if ((settings.value.height || 0) < 1080) {
+          rtcWarn(
+            'capture below 1080p — pick a full monitor (window capture is limited to the window size)',
+            { width: settings.value.width, height: settings.value.height },
+          )
+        }
+        videoTrack.addEventListener('ended', () => {
+          stopShare()
+        })
+      }
 
       return { stream, streamId: streamId.value }
     } catch (e) {
@@ -42,11 +67,12 @@ export function useScreenShare() {
     localStream.value?.getTracks().forEach((t) => t.stop())
     localStream.value = null
     streamId.value = null
+    settings.value = null
   }
 
   onBeforeUnmount(() => {
     stopShare()
   })
 
-  return { localStream, streamId, isSharing, error, startShare, stopShare }
+  return { localStream, streamId, settings, isSharing, error, startShare, stopShare }
 }