Is there a generic ScreenSpaceEvent that captures all events?

Question

To react to specific space handlers I typically do this -

var fooHandler = new Cesium.ScreenSpaceEventHandler(viewer.scene.canvas);
fooHandler.setInputAction(function(movement){
    // do stuff
}, Cesium.ScreenSpaceEventType.WHEEL);

This function would be limited to WHEEL inputs. I have a couple of things that I need to do every time the camera changes position or height. I tried creating an event handler for the camera in a fashion similar to the above, and then calling camera.positionCartographic within that function, but to no avail.

Is there an event in Cesium that captures any movement?

Answer 1

You don't want to use ScreenSpaceEventHandler to do this. Instead, you subscribe to the preRender event and compare the camera position from last frame. Here's some sample code for you:

var lastTime = Cesium.getTimestamp();
var lastPosition = viewer.scene.camera.position.clone();

function preRender(scene) {
    var time = Cesium.getTimestamp();
    var position = scene.camera.position;
    if (!Cesium.Cartesian3.equalsEpsilon(lastPosition, position, Cesium.Math.EPSILON4)) {
        document.getElementById('viewChanged').style.display = 'block';
        lastTime = time;
    } else if (time - lastTime > 250) {
        //hide the 'view changed' message after 250 ms of inactivity
        lastTime = time;
        document.getElementById('viewChanged').style.display = 'none';
    }
    lastPosition = position.clone();
}

viewer.scene.preRender.addEventListener(preRender);

We plan on adding a viewChanged event to Cesium some time soon, perhaps with 1.8, but this code will continue to work after that and you'll be able to switch to the event at your leisure.

If you want a live demo of the above code, see this port of the view changed Google Earth demo we did in Cesium: http://analyticalgraphicsinc.github.io/cesium-google-earth-examples/examples/viewchangeEvent.html