345050 - Turning off spellchecking is very slow when there are many misspellings.

Status: RESOLVED FIXED

(Core :: Spelling checker, defect)

Description

[Brett Wilson]

For example, go here:
  http://en.wikipedia.org/w/index.php?title=Jimi_Hendrix&action=edit
Without the patch on bug 344895, it might take many minutes to see. Then turn off spellchecking with the context menu for the textarea. It takes a noticeable amount of time.

The problem is in RemoveAllRanges() on the spellcheck selection. It iterates over all ranges and calls nsTypedSelection::selectFrames for each of them. This function is pretty scary, and is likely the cause of the slowness.

Comment 1

[Brett Wilson]

This bug also causes slowness in "Add to dictionary" for large textareas. See 345059.

Comment 2

[Boris Zbarsky [:bzbarsky]]

Attachment: Profile

Overall:

Total hit count: 100899

100679 of them under nsTypedSelection::selectFrames, almost all of it under nsTextFrame::SetSelected.  Almost all the time under SetSelected is under nsFrameSelection::LookUpSelection.  This is called to find the details to delete, if any, as far as I can tell.  The problem is that it iterates over all ranges and for each one checks whether our text frame's range intersects it.

So the net result is that RemoveAllRanges() on the selection is O(N^2) in the number of ranges.  Since we have a _lot_ of ranges here, things are really slow.  There's got to be a better way to do this from the selection's point of view, since it _knows_ all the ranges are being removed...  If someone more familiar with this details stuff would look at this, that would be great.

Comment 3

[Brett Wilson]

Fixed by bug 345099.