Bad performance on selection change checks

[Frederico Caldeira Knabben]

There is a really bad performance in the tasks being fired when the selection changes in the editor. To check it:

1. Clean load a sample.
2. With a mouse click, place the cursor inside any unformatted word, like "are".
3. Open the Firebug console and start a Profile job. Don't do anything in the editor, not even a mouseover in the toolbar buttons.
4. Click inside a bold word, like "sample". Again, don't do anything else in the editor.
5. Stop the Profile job.

The profiler will show you an excessive number of calls.

In IE6 this bad performance is terribly noticeable, compromising the editor usage.

Performance excellence is definitely important for this feature.

[Garry Yao]

This is related to #2927, which raise the state computation to O(n²), where n stand for number of commands.

[Garry Yao]

The patch in #2927 could almost resolve the bug on this ticket.

[Frederico Caldeira Knabben]

The situation is much more stable now. There may be room for improvements, but this is not anymore a critical issue.