Bug Tracker

Opened 7 years ago

Closed 6 years ago

Last modified 6 years ago

#6942 closed enhancement (fixed)

JQuery.event.fix causes unnecessary reflows in IE when handling key events

Reported by: scott_h Owned by: dmethvin
Priority: blocker Milestone: 1.7
Component: event Version: 1.4.2
Keywords: performance, reflow, 1.7-discuss Cc:
Blocked by: Blocking:

Description (last modified by dmethvin)

When normalising the event object, jQuery adds pageX/pageY properties in IE based on a combination of event.clientX/Y and document.body.scrollLeft/Top.

More Information

Accessing scrollLeft/Top on the body triggers a full-page reflow. On a large DOM, this makes jQuery's key* event handlers unnecessarily slow in IE7 and IE8, since pageX/Y are useless for key events (and so could be defined without triggering reflows).

Interestingly, I discovered that IE defines clientX/Y on key* events to be the current mouse position, whereas in Safari/Firefox they (along with pageX/Y) are both 0. This inconsistency makes me sure that no one uses jQuery's pageX/Y on key events.

Attachments (1)

jQuery.event.fix-dynaTrace.png (23.2 KB) - added by scott_h 7 years ago.
dynaTrace PurePaths tab showing poor performance on a keydown event

Download all attachments as: .zip

Change History (22)

Changed 7 years ago by scott_h

dynaTrace PurePaths tab showing poor performance on a keydown event

comment:1 Changed 7 years ago by scott_h

Here's the fix I propose for this bug:

http://github.com/shghs/jquery/commit/b59718e2dab80a8a92d7a02a427e60e1da06bd20

I've verified that the test suite passes in Safari 5.0.1 (Mac), Firefox 3.6.8 (Mac), IE7 (WinXP) and IE8 (WinXP) with this change.

comment:2 Changed 7 years ago by snover

Milestone: 1.4.31.next
Priority: low
Status: newopen
Type: bugenhancement

I like this. Please make a pull request for your patch if it is still unresolved in 1.4.3. If it is resolved, please let us know so we can close this ticket.

comment:3 Changed 7 years ago by snover

Milestone: 1.4.41.5

Retarget all enhancements/features to next major version.

comment:4 Changed 7 years ago by john

Milestone: 1.next

Let's look at this for 1.7.

comment:5 Changed 7 years ago by john

Description: modified (diff)

comment:6 Changed 7 years ago by john

Keywords: 1.7-discuss added

Nominating ticket for 1.7 discussion.

comment:7 Changed 7 years ago by Rick Waldron

Description: modified (diff)

+1, Seems like a bug, should be fixed

comment:8 Changed 7 years ago by jaubourg

+1, no brainer

comment:9 Changed 6 years ago by ajpiano

Description: modified (diff)

+1, Ew, unnecessary reflows in IE is like kicking somone when they're down... fix!

comment:10 Changed 6 years ago by timmywil

Description: modified (diff)

+1, ouch

comment:11 Changed 6 years ago by paul.irish

Description: modified (diff)

+1, it'd also be worthwhile to take a hard look at the rest of the event props we are copying over. see if theres any more we can cull

comment:12 Changed 6 years ago by john

Description: modified (diff)

+1, Let's fix this, absolutely.

comment:13 Changed 6 years ago by scottgonzalez

+1

comment:14 Changed 6 years ago by addyosmani

+1

comment:15 Changed 6 years ago by jzaefferer

+1

comment:16 Changed 6 years ago by dmethvin

Description: modified (diff)
Milestone: 1.next1.7

comment:17 Changed 6 years ago by dmethvin

Priority: lowblocker

comment:18 Changed 6 years ago by dmethvin

Owner: set to dmethvin
Status: openassigned

comment:19 Changed 6 years ago by anonymous

Sorry for deleting the repo linked above. I've issued a pull request with a slightly cleaner fix compared to the original one:

https://github.com/jquery/jquery/pull/452

but I am skeptical that this is actually a bug. I think this needs to be stress tested on a page with lots of elements.

comment:20 Changed 6 years ago by timmywil

@rwaldron: can we add this to event property hooks?

comment:21 Changed 6 years ago by dmethvin

Resolution: fixed
Status: assignedclosed

Fixed along with #8789 refactor.

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