Fire "beforeunload" confirm box only if document has changes

[sdumetz]

This box is annoying. The save process is complicated enough (save scene, capture pose, save article), if users can't rely on this to know if they forgot to save something they will just ignore the dialog because it's wrong most of the time anyway.

Serializing the CVDocument just after openDocument() and serializing again to compare the string value in CVStoryApplication.beforeunload() might do the trick but I'd like a solution that allows a better UI (eg: highlighting the save button as soon as the doc is changed). The tricky bit is that we have no representation of the document's data once it's been loaded into the graph, so a "changed" switch seems hard to implement.

I'd like to work on this issue, if anyone has an idea worth trying.

[gjcope]

I agree the box would be better served only when the data is dirty, but still better there than not. Several components already have literal or effective 'changed' output events, so a state manager could subscribe to those events to flip the global changed state and clear on save. The hard part would be adding the missing events and making sure coverage is 100%.