IE11 - Typing is slow after pasting for the second time into editor.

[Jakub Ś]

Steps to reproduce

1. Open attached 27 page document and paste it into editor.
2. Start typing immediately after paste. Document is being still processed so first characters my not show up but later on you can type without problems
3. Press Ctrl+A and Backspace (you can press delete and backspace few times - it doesn't matter)
4. Paste text again and again after the text shows up start typing.

Actually you can wait few seconds and then start typing.

Expected result

Typing speed should be normal.

Actual result

Typing is very slow even after few minutes.

Other details (browser, OS, CKEditor version, installed plugins)

Problem can be reproduced in IE11 only. IE11 is supported from CKEditor 4.3 but I have seen this issue even in CKEditor 4.0.

[Tade0]

I did a few test, here are the results:

-Going through the steps on a VirtualBox VM with 128MB video memory reproduces the problem even at step 2.

-Changing the video memory to 256MB (max available) makes the problem appear at step 4.

-After step 4. the profiler shows, that the vast majority of processing power is dedicated to handling the native innerHtml method.

[Marek Lewandowski]

Rather than video memory it should depend on system RAM memory. Set it simply to something like 2gb and then see the results.

Also compare how does it work for IE10, IE9, Edge - is IE11 the only one browser having this problem?

[Tade0]

Tested it on IE8, IE11 and Edge. Among them only IE11 seems to have this "feature".

[Jakub Ś]

One of our users/customers have provided temporary workaround.

Recently we found out that typing becomes faster if you activate and deactivate the “Source Code” mode after pasting the large document into the CKEditor instance.

/**
* Workaround for pasting problems with IE11
*/
CKEDITOR.plugins.add('iepaste-workaround', {
       init : function(editor) {
             if(CKEDITOR.env.ie) {
                    editor.on('paste', function(evt) {// Show screen lock
                    });
                    editor.on('afterPaste', function(evt) {
                           var editor = evt.editor;
                           var bookmarks = editor.getSelection().createBookmarks2();
                           editor.setData(editor.getData(), {
                                  callback: function() {
                                         try {
                                               var selection = editor.getSelection();
                                               selection.selectBookmarks(bookmarks);
                                               selection.scrollIntoView();

                                        } finally {
                    // Close screen lock
                                        }
                                  }
                           });
                    });
             }
      }
});

[Tomasz Jakut]

It seems that problem is caused by ​selecting range after inserting pasted data into it. Everything works fine without touching the range.

Moreover it could be bug in IE with handling native selections as simplifying our handler for selecting ranges does not solve the problem.

[Marek Lewandowski]

This issue is really complex, we're unable to squeeze it into 4.5.7.

[Tomasz Jakut]

The problem could be easily reproduced outside the CKEditor, as ​shown in that demo.

Bug was ​reported to MS.

[Tomasz Jakut]

Issue in IE's bug tracker is marked as ​won't fix.