Magicline out of the editable

[Olek Nowodziński]

Since magicline is injected into editable in brings a lot of problems, especially in old IEs:

• content flickering
• unexpected scrollbars
• problems with copying
• and so on...

The idea is to keep magicline outside of the editor in a top-level document, pretty much the same way like dialogs and panels. The problem might be the CSS interaction with existing styles, which needs to be considered.

Related issues

#11270

[Olek Nowodziński]

Created branch t/9400 with a magicline in the top-level document. It hasn't been checked under IE7 yet.

This change brings a speed boost of about ~10% (especially in Firefox) and bypasses all editable-related issues.

Things to consider:

1. It would be great if we could use CSS class to change the look the the line instead of JS (possible speed boost). However it means that additional CSS (<style> tag) must be injected into a top-level document. Isn't it too much?
2. Does the compatibility with outer-page CSS is preserved?
3. Something else?

[Olek Nowodziński]

The solution of this problem is Lineutils plugin introduced in #10933.