Can, and should, I implement "desktop" apps in the browser?

I need to develop something cross-platform.

I had been considering Java but was wondering how to distribute my app in the first place and how to distribute upgrades and I go to thinking how much simpler things would be if my app were browser based.

I suppose it all depends what I want my app to do ...

• I want to download some documents, movies, mp3s, store them and allow the user to select them to read, view or listen to.
• I also want the documents to be encrypted and decrypt them on the fly for usage, so that they cannot be accessed if the device is lost

Just in case of feature creep, and out of general curiosity, I wonder if anyone has any general points to make about what I can and can't do to the local PC.

• I suppose that accessing hardware would be tricky
• I may need to have some platform -specific handling of directory structure
• ditto executing shell commands (for encryption)

Anything else? Is it a ba开发者_运维技巧d idea to even consider this?

It sounds like you want air. You can do a "web app" that's pretty well platform independent and runs locally with permissions more or less like a regular application.

It also has a nice built in encrypted data store.

If you do want to develop a "desktop" app in a browser, I recommend ExtJS, a full stack javascript framework. It has a lot of rich GUI components for giving your application a desktop feel and a large, supportive community.