FYI: http://fmbip.com/ tells you about your current browser compatibility.
Uses for HTML5:
- Drag and Drop File API for uploading attatchments, avatars etc. - Drag and drop files from your desktop to upload
- Local Client-side Storage - Saves text box content locally so if your browser crashes, your post/topic is saved (I have done this too many times)
- Application Cache - Probably best left for 4.0 but allows you to cache a webpage (a topic) locally so you can refresh and view it offline.
- Desktop Notifications - Shows popup on desktop (for PM's instead of popup windows and maybe more uses).
- Desktop Drag Out - Drag Files (Attatchments) from in your browser onto your desktop.
- Speech Input - Allows user to talk to insert text into the text field.
- Upload progress bars - Shows how much has uploaded and how far to go.
- Update Input Types - To make use of the new HTML5 Input Types
- I doubt there will be a prosilver tags overhaul and we need some backwards compatibility so I won't even go any further with that.
- Form Field Types - For more mobile compatibility, it tells the mobile device what keyboard to use. Number, Email or general text are the main ones phpBB will use. This will be more prominent in the ACP.
- Playing attachments directly in browser if a video or mp3.
- Colour Wheel - I don't know very much about this but I hear you could use inline colour wheel, perhaps on a jQuery Popup?
- Text Warping/Overflow - Size of text fields
- Gradient Usage - Instead of images, gradients could be used.
- Rounded Corners - I believe these have already been mentioned
Thats just a small selection of some times it could be used to make the UI more slick. This is most certainly a 3.2 change and not 3.1 due to the compatibility with browsers.
I have listed many uses, if all were used then some things would be missing and it would have been overused at the same time.
Here is the place to discuss which HTML5 could be used as well as if it will be used.