TinyMCE move cursor

I'd like to write a tinyMCE plugin that allows the nesting of sub and sup tags.

Right now I've written a command that inserts raw HTML 开发者_如何学Python'' at the cursor when you push the button / hit the shortcut keys. However, this will only work if I can then move the cursor to the middle of the new tag.

I can't seem to find any documentation on how to move the cursor. There are some suggested hacks, but they are very hacky. This can't be that hard because, as I understand it, this is how the [b] and [i] buttons work too.

Is there a better way to be doing this? How can I write a tinyMCE function that puts the user in "sub mode" or "sup mode" and allows them to nest "sub" and "sup" modes?

Thanks!

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This function will set the cursor to the specified html element.

// sets the cursor to the specified element, ed ist the editor instance
// start defines if the cursor is to be set at the start or at the end
setCursor: function (ed, element, start) {

    var doc = ed.getDoc();
    if (typeof doc.createRange != "undefined") {
        var range = doc.createRange();
        range.selectNodeContents(element);
        range.collapse(start);
        var win = doc.defaultView || doc.parentWindow;
        var sel = win.getSelection();
        sel.removeAllRanges();
        sel.addRange(range);
    } else if (typeof doc.body.createTextRange != "undefined") {
        var textRange = doc.body.createTextRange();
        textRange.moveToElementText(element);
        textRange.collapse(start);
        textRange.select();
    }
},

In order to nest sups you need to make sure that sups and subs may be nested. Please check the extended_valid_elements and valid_elements configuration parameter. sub and sup may not be nested by default! You need to overwrite this part of the ruleset.