From a23d107343891d7577ab8a4c8ed467f6033eb276 Mon Sep 17 00:00:00 2001
From: automated-signal <37887102+automated-signal@users.noreply.github.com>
Date: Wed, 16 Oct 2024 12:48:18 -0500
Subject: [PATCH] Add minimum frame rate constraint for screen share

---
 package-lock.json          |  8 ++---
 package.json               |  2 +-
 ts/util/desktopCapturer.ts | 66 +++++++++++++++++++++++++++++---------
 3 files changed, 56 insertions(+), 20 deletions(-)

diff --git a/package-lock.json b/package-lock.json
index 7381829ecaf7..f1252896ef1d 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -14,7 +14,7 @@
         "@formatjs/icu-messageformat-parser": "2.3.0",
         "@formatjs/intl-localematcher": "0.2.32",
         "@indutny/dicer": "0.3.2",
-        "@indutny/mac-screen-share": "1.0.11",
+        "@indutny/mac-screen-share": "1.0.13",
         "@indutny/range-finder": "1.3.4",
         "@indutny/simple-windows-notifications": "2.0.7",
         "@indutny/sneequals": "4.0.0",
@@ -4086,9 +4086,9 @@
       }
     },
     "node_modules/@indutny/mac-screen-share": {
-      "version": "1.0.11",
-      "resolved": "https://registry.npmjs.org/@indutny/mac-screen-share/-/mac-screen-share-1.0.11.tgz",
-      "integrity": "sha512-0UHiWyUBYn3VjjwpaS0nD6bppunyaTdFGXU84uGmzlV1R9RYcXQOF4EDCWQLpMlw4TieLOBvsh10gLEP116MPw==",
+      "version": "1.0.13",
+      "resolved": "https://registry.npmjs.org/@indutny/mac-screen-share/-/mac-screen-share-1.0.13.tgz",
+      "integrity": "sha512-fCOYWGaIuZAwfk/eUUjqPKge4+PKKCwTsuH9SSoaBZMP8IsWQtyyrTVpeuq84oDren4b9EUgRGgh2t950sQA0w==",
       "hasInstallScript": true,
       "license": "MIT",
       "dependencies": {
diff --git a/package.json b/package.json
index bd310c94a34e..9c87128ec54b 100644
--- a/package.json
+++ b/package.json
@@ -98,7 +98,7 @@
     "@formatjs/icu-messageformat-parser": "2.3.0",
     "@formatjs/intl-localematcher": "0.2.32",
     "@indutny/dicer": "0.3.2",
-    "@indutny/mac-screen-share": "1.0.11",
+    "@indutny/mac-screen-share": "1.0.13",
     "@indutny/range-finder": "1.3.4",
     "@indutny/simple-windows-notifications": "2.0.7",
     "@indutny/sneequals": "4.0.0",
diff --git a/ts/util/desktopCapturer.ts b/ts/util/desktopCapturer.ts
index 7fe8c346ecbd..0c24289e8b1e 100644
--- a/ts/util/desktopCapturer.ts
+++ b/ts/util/desktopCapturer.ts
@@ -18,6 +18,8 @@ import { strictAssert } from './assert';
 import { explodePromise } from './explodePromise';
 import { isNotNil } from './isNotNil';
 import { drop } from './drop';
+import { SECOND } from './durations';
+import { isOlderThan } from './timestamp';
 
 // Chrome-only API for now, thus a declaration:
 declare class MediaStreamTrackGenerator extends MediaStreamTrack {
@@ -176,19 +178,26 @@ export class DesktopCapturer {
     liveCapturers.add(this);
     try {
       const stream = await navigator.mediaDevices.getDisplayMedia({
-        video: {
-          width: {
-            max: REQUESTED_SCREEN_SHARE_WIDTH,
-            ideal: REQUESTED_SCREEN_SHARE_WIDTH,
-          },
-          height: {
-            max: REQUESTED_SCREEN_SHARE_HEIGHT,
-            ideal: REQUESTED_SCREEN_SHARE_HEIGHT,
-          },
-          frameRate: {
-            max: REQUESTED_SCREEN_SHARE_FRAMERATE,
-            ideal: REQUESTED_SCREEN_SHARE_FRAMERATE,
-          },
+        video: true,
+      });
+
+      const videoTrack = stream.getVideoTracks()[0];
+      strictAssert(videoTrack, 'videoTrack does not exist');
+
+      // Apply constraints and ensure that there is at least 1 frame per second.
+      await videoTrack.applyConstraints({
+        width: {
+          max: REQUESTED_SCREEN_SHARE_WIDTH,
+          ideal: REQUESTED_SCREEN_SHARE_WIDTH,
+        },
+        height: {
+          max: REQUESTED_SCREEN_SHARE_HEIGHT,
+          ideal: REQUESTED_SCREEN_SHARE_HEIGHT,
+        },
+        frameRate: {
+          min: 1,
+          max: REQUESTED_SCREEN_SHARE_FRAMERATE,
+          ideal: REQUESTED_SCREEN_SHARE_FRAMERATE,
         },
       });
 
@@ -222,6 +231,20 @@ export class DesktopCapturer {
 
     let isRunning = false;
 
+    let lastFrame: VideoFrame | undefined;
+    let lastFrameSentAt = 0;
+
+    let frameRepeater: NodeJS.Timeout | undefined;
+
+    const cleanup = () => {
+      lastFrame?.close();
+      if (frameRepeater != null) {
+        clearInterval(frameRepeater);
+      }
+      frameRepeater = undefined;
+      lastFrame = undefined;
+    };
+
     const stream = new macScreenShare.Stream({
       width: REQUESTED_SCREEN_SHARE_WIDTH,
       height: REQUESTED_SCREEN_SHARE_HEIGHT,
@@ -230,6 +253,17 @@ export class DesktopCapturer {
       onStart: () => {
         isRunning = true;
 
+        // Repeat last frame every second to match "min" constraint above.
+        frameRepeater = setInterval(() => {
+          if (isRunning && track.readyState !== 'ended' && lastFrame != null) {
+            if (isOlderThan(lastFrameSentAt, SECOND)) {
+              drop(writer.write(lastFrame.clone()));
+            }
+          } else {
+            cleanup();
+          }
+        }, SECOND);
+
         this.options.onMediaStream(mediaStream);
       },
       onStop() {
@@ -253,13 +287,15 @@ export class DesktopCapturer {
           return;
         }
 
-        const videoFrame = new VideoFrame(frame, {
+        lastFrame?.close();
+        lastFrameSentAt = Date.now();
+        lastFrame = new VideoFrame(frame, {
           format: 'NV12',
           codedWidth: width,
           codedHeight: height,
           timestamp: 0,
         });
-        drop(writer.write(videoFrame));
+        drop(writer.write(lastFrame.clone()));
       },
     });