Make CKEditor 4 works in strict mode

[SuperPat45]

Type of report

Bug

Provide detailed reproduction steps (if any)

1. Simply add "use strict"; at the beginning of the compiled ckeditor.js

Expected result

It should work

Actual result

An exception is thrown:

TypeError: this is undefined
getClientRects http://localhost:8080/ckeditor.js:12586
<anonymous> http://localhost:8080/ckeditor.js:12805
<anonymous> http://localhost:8080/ckeditor.js:12934
<anonymous> http://localhost:8080/ckeditor.js:64500

Other details

The error is in the getClientRects function of the range.js source, where this is undefined in strict mode:

getClientRects: ( function() {
	if ( this.document.getSelection !== undefined ) {
		return function( isAbsolute ) {
			// We need to create native range so we can call native getClientRects.
			var range = this.root.getDocument().$.createRange(),
				rectList;

			range.setStart( this.startContainer.$, this.startOffset );
			range.setEnd( this.endContainer.$, this.endOffset );

			rectList = range.getClientRects();

			rectList = fixWidgetsRects( rectList, this );

			if ( !rectList.length ) {
				rectList = fixEmptyRectList( rectList, range, this );
			}

			return CKEDITOR.tools.array.map( rectList, function( item ) {
				return convertRect( item, isAbsolute, this );
			}, this );
		};
	} else {
		return function( isAbsolute ) {
			return [ convertRect( getRect( this.createBookmark() ), isAbsolute, this ) ];
		};
	}

There is probably other bugs to fix in strict mode

• Browser: Firefox 96
• OS: Windows 10
• CKEditor version: 4.17.1
• Installed CKEditor plugins: Full preset

[Comandeer]

I can confirm the issue.

[CKEditorBot]

Closed in #5141