Source Area
The CodeMirror plugin extends the source area of the framed CKEditor, with the source area you can edit the raw HTML content of an editor with Syntax Highlighting.
To enable this
plugin, basically add extraPlugins: 'codemirror' to editor's
config:
// Framed editor.
CKEDITOR.replace( 'textarea_id', {
extraPlugins: 'codemirror'
});