Huzzah! I found the solution! No need to make changes to XF. The solution is some custom JS code that is run in the parent document that contains the <iframe>. This is the code I wrote (it uses jQuery but I'm sure it can be done without jQuery):
/* because ios safari is too stupid to handle iframe content height changes
* properly we have to apply this workaround to set the iframe height manually
*/
$('iframe').load(function() {
var self = this;
function resizeiframe(eventObject) {
var height = $(self.contentWindow.document).height();
$(self).css("height", height);
}
resizeiframe();
$(self.contentWindow).resize(resizeiframe);
});
In other words - setting the "height" css value of the <iframe> to the content height fixes the jumping issue. The JS code updates the height value whenever the height of the contents change. This of course will only work on same origin contents.
