FocusGram-Android/v2/autoplay_blocker.js

/**
 * FocusGram Autoplay Blocker
 * Injected at DOCUMENT_START — before Instagram's JS loads.
 * Prevents video autoplay by:
 * 1. Blocking play() calls on video elements
 * 2. Disabling autoplay attribute
 * 3. Removing preload attributes
 */
(function () {
  'use strict';

  window.__fgBlockAutoplay = false;

  // Override HTMLMediaElement.play() to check our flag
  const _play = HTMLMediaElement.prototype.play;
  HTMLMediaElement.prototype.play = function () {
    if (window.__fgBlockAutoplay) {
      // Return a resolved promise to avoid breaking Instagram's code
      return Promise.resolve();
    }
    return _play.call(this);
  };

  // Override autoplay property setter
  const _videoDescriptor = Object.getOwnPropertyDescriptor(HTMLVideoElement.prototype, 'autoplay') || {};
  const _originalAutoplaySetter = _videoDescriptor.set;

  Object.defineProperty(HTMLVideoElement.prototype, 'autoplay', {
    set: function (value) {
      if (window.__fgBlockAutoplay && value) {
        // Silently ignore autoplay attempts when blocking is enabled
        return;
      }
      if (_originalAutoplaySetter) {
        _originalAutoplaySetter.call(this, value);
      }
    },
    get: function () {
      if (_videoDescriptor.get) {
        return _videoDescriptor.get.call(this);
      }
      return this.getAttribute('autoplay') !== null;
    },
    enumerable: _videoDescriptor.enumerable,
    configurable: true,
  });

  // On page load and SPA navigation, scan for video elements and remove autoplay
  const removeAutoplayFromVideos = () => {
    document.querySelectorAll('video, [role="video"]').forEach(el => {
      if (window.__fgBlockAutoplay) {
        el.autoplay = false;
        el.removeAttribute('autoplay');
        if (el.paused === false) {
          el.pause();
        }
      }
    });
  };

  // Run on load and when document changes
  removeAutoplayFromVideos();

  if (!window.__fgAutoplayObserver) {
    let _timer = null;
    window.__fgAutoplayObserver = new MutationObserver(() => {
      clearTimeout(_timer);
      _timer = setTimeout(removeAutoplayFromVideos, 500);
    });
    window.__fgAutoplayObserver.observe(document.documentElement, {
      childList: true,
      subtree: true,
    });
  }

  // Allow Flutter to toggle
  window.__fgSetBlockAutoplay = function (enabled) {
    window.__fgBlockAutoplay = !!enabled;
    if (enabled) {
      removeAutoplayFromVideos();
    }
  };
})();