<!DOCTYPE html>
<html>
<head>
  <title>Lottie Filmstrip Capture</title>
  <meta charset="utf-8" />
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <script src="/lottie.js" type="text/javascript" charset="utf-8"></script>
  <style type="text/css" media="screen">
    body,
    main,
    .anim {
      margin: 0;
      padding: 0;
    }

    main {
      display: flex;
      width: 1000px;
      height: 1000px;
      flex-flow: row wrap;
    }
  </style>
</head>
<body>
  <main>
    <div class=anim></div>
  </main>
  <script type="text/javascript" charset="utf-8">
    (function () {
      const TILE_COUNT = 5; // Number of tiles in x or y direction.
      const TARGET_SIZE = 1000; // Image size in pixels both x and y direction.
      const PATH = '/lottie.json';

      let renderer = 'svg';
      let hash = window.location.hash;
      if (hash) {
        renderer = hash.slice(1);
      }

      // This global is used by puppeteer to determine if all tiles have finished drawing.
      window._tileCount = 0;

      // First load the animation for just a single tile
      // so we can read out some values and calculate what
      // the filmstrip should look like.
      let anim = lottie.loadAnimation({
        container: document.querySelector('.anim'),
        renderer: renderer,
        loop: false,
        autoplay: true,
        path: PATH,
        rendererSettings: {
          preserveAspectRatio:'xMidYMid meet'
        },
      });

      anim.addEventListener('data_ready', (e) => {
        // Once the first tile is loaded, calculate what
        // the filmstrip should look like.
        let animationData = anim.animationData;
        let totalFrames = anim.totalFrames;
        // t_rate mimics DMSrcSink.cpp::SkottieSrc::draw
        let t_rate = 1.0 / (TILE_COUNT * TILE_COUNT - 1);

        let main = document.querySelector('main');

        // Clear out the first div now that our measurements are done.
        main.firstElementChild.remove();

        // Add in all the tiles.
        for (let i = 0; i < TILE_COUNT*TILE_COUNT; i++) {
          let div = document.createElement('div');
          div.classList.add('anim');
          div.style.width = (TARGET_SIZE / TILE_COUNT) + 'px';
          div.style.height = (TARGET_SIZE / TILE_COUNT) + 'px';
          main.appendChild(div);

          // create a new animation for each tile. It is tempting to try having
          // one animation and "clone" each frame, but that doesn't work
          // because of how bodymovin cleans up the URLObjects that are the path
          // data for the svgs.
          // We can re-use the animationData to avoid having to hit the
          // (local) network a bunch of times.
          let anim = lottie.loadAnimation({
            container: div,
            renderer: renderer,
            loop: false,
            autoplay: false,
            animationData: animationData,
            rendererSettings: {
              preserveAspectRatio:'xMidYMid meet'
            },
          });

          let t = Math.max(Math.min(t_rate * i, 1.0), 0.0);
          let seekToFrame = totalFrames * t;
          if (seekToFrame >= totalFrames) {
            // bodymovin player sometimes draws blank when requesting
            // to draw the very last frame.  Subtracting a small value
            // seems to fix this and make it draw the last frame.
            seekToFrame -= .001;
          }

          // don't need to wait for data_ready because it's instantly ready.
          console.log(`t = ${t}, go to frame ${seekToFrame}`);
          anim.goToAndStop(seekToFrame, true);
          window._tileCount += 1;
        }
      });
    })();
  </script>
</body>
</html>