examples/viewers_upload/viewers_upload.js
function onWindowKeyPressed(event) {
      ctrlDown = event.ctrlKey;
      if (!ctrlDown) {
        drag.start.x = null;
        drag.start.y = null;
      }
    }
function onWindowKeyPressed(event) {
      ctrlDown = event.ctrlKey;
      if (!ctrlDown) {
        drag.start.x = null;
        drag.start.y = null;
      }
    }
On key pressed callback