Cross-platform GUI for windows / osx / ipad

I am doing a summer project, which includes completely rewriting a large application to be more modern and cross-platform compatible. It should work on Windows, OS X and iPad. IPad assembly is a priority. It is preferable that in the future it will be quite easy to convert to a web application.

My current plan is to make the entire GUI in HTML / CSS / JS using the Chrome Embedded Framework to render pages and handle interactivity. Thus, the entire user interface is a cross-platform for everything, and I just need to write specific platform code to display it. It also means that if / when I transfer it to the Internet, most of the user interface is already in an Internet-compatible format. The rest of the application code should be mostly cross-platform, but just pure C ++. There is no CEF for the iPad, so I'm considering using the UIWebView class to do the same. I'm curious what you are doing using HTML as a GUI on iPad.

My main concerns:

• Performance. I do not know what the UIWebView performance characteristics are, as far as this is applicable for the graphical interface. There will be many interactive dialogs and even animations. I did some research on how you communicate with Objective-C with Javascript, and the most popular method (setting the location of the document to some custom URL such as MyApp: //, and extracting the message from the string) seems to be very slow

• Usability - iOS users are used for a certain standard of interactivity (for example, really smooth transitions, draggable sidebars, everything is fast and polished). I'm sure I can do this on Windows / OS X using CEF, but not sure about the iPad.

Thank you for your time!