This is an experiment to showcase a progressive web application that interacts with Cesium library. It demonstrates how we can cache arbitrary imagery content and make an application - built with Cesium - faster to load using Progressive Web application techniques. It specifically uses a strategy called cache-then-network to fetch and cache imagery data from OpenStreetMaps, although other providers could be used.
While the user navigates inside the viewer, imagery data are cached locally using the service worker. Alongside, the current location and orientation of the camera are kept locally in localStorage. Next time the user opens the application, being offline or not, he will be directed to its last known location with all imagery loaded instantly and fast.
You can test a fully functional working live demo at https://pxcesium.azurewebsites.net/pwa/.
- Limit of the Cache Storage that keeps imagery data. We may need to implement a mechanism so that it refreshes as soon as new data arrive. Maybe set an internal limit and keep only the last (n) records.
- We should use a local copy of Cesium and not one from the official Cesium website because
cache.addAll()is atomic, If any of the files fail, the entire cache addition fails! - Investigate sw-toolbox and sw-precache libraries for production enviroments.