Event Model - responding to user moving and zooming

[tomcrane]

Comments from Getty:

It would be useful to understand an event model which would allow us to interact with a user’s adjustment of the ImageService or Canvas – A couple of examples here –

• Implementing Zoom or Home buttons for an image viewer. We need to know the current state of the viewer so we can disable these buttons when the user has zoomed in to the max, or zoomed out.
• A mini navigation viewer – if we rolled our own, we need to know when an image service has changed so we can updated where the box shows on the navigation (note the navigation here doesn’t work)
• Firing a @change event which included both the target (x,y,w,h) as well as the current zoom level might suffice for the basic functionality, but finer grain events might also be useful
• Is there a way to get the min-zoom or max-zoom for an ImageService when loaded? Again, useful for managing button state.

[stephenwf]

Fire events for each time the viewport changes will be quite noisy, but we should add events for hitting min and max zoom that you could use to enable/disable buttons.