29186 - onMouseOver really fast makes image disappear for a second

Status: VERIFIED DUPLICATE of bug 20110

(Core :: Graphics: ImageLib, defect, P3)

Description

[Arnoud Berendsen]

When using PNG images in a menu with an onMouseOver, it sometimes takes a while 
before the new image is displayed. The faster you move the mouse, the worse it 
gets, especially if you move over the menu in a vertical way. This also seems to 
happen with other image formats, like GIF and JPG, but not nearly as often. (I 
have but a PNG, GIF and JPG version of the same menu at the above URL)

Another thing is that when you move the mouse out of the image area too fast, 
the onmouseout does not always work, and the old image hangs in there.

These things might be two different things, but might also be tied together, as 
far as I can tell.

Comment 1

[Alan S. Jones]

Very interesting bug.  We were not sure what was the best component for this.  
It is partly image related.
Direct link to the PNG version that is esay to reprodice
http://www.xs4all.nl/~berendse/moztest/png/menu.html

Direct link to the JPG version that is sorta easy to reproce
http://www.xs4all.nl/~berendse/moztest/jpg/menu.html

Direct link to the GIF version that is harder to reproduce
http://www.xs4all.nl/~berendse/moztest/gif/menu.html

Comment 2

[pnunn]

I'm not seeing this on NT. I'll see if I can dig up
a win2000 machine somewhere. Anyone notice this problem
on any other platforms? 

Could you give us more info on the win2000 machine?
How fast? How much ram? 
thanks, 
pn.

Comment 3

[Alan S. Jones]

Sorr, i should have added when I saw this bug from [e-mail] i was on 
Win95.

Comment 4

[Arnoud Berendsen]

Which of these two issues aren't you seeing on NT? The problem that images 
"hang" sometimes even after onmouseout should've executed, or the one that the 
PNG images disappear for a moment if you mouseover really fast? (It happens with 
GIF and JPG only rarely. I haven't been able to figure out when exactly it 
does.)

When I found and reported this bug I was on a P1-225MHz machine with 80MB RAM 
and Win2000. I later checked this on a P2-400 with 128MB (also running Win2k). 
The problem with the lag in displaying the PNG images seemed much less on that 
machine, but it was still quite easy to reproduce. I was unable to reproduce the 
lag in the GIF and JPG images on that machine (but that was already hard to 
reproduce even on the slower system). It seems to me the mouseOver wants to 
display the new image too "eagerly", even before the new image is loaded, so the 
problem doesn't show that much on faster systems (that can load the images 
faster).

As for the onMouseOut not displaying the correct image after leaving the image 
area, I have traced that down to be a scripting bug! (That, most likely, makes 
this a completely different bug from the above, so maybe it's best to split this 
Bugzilla bug in two...). Look at the, perhaps somewhat unconventional, script 
for changing between images:

path = "images/"
on = "_on.png"
off = "_off.png"
function switchimg(img)
{ if (document.images[img].src.indexOf(on) != -1)
document.images[img].src = path + img + off;
else document.images[img].src = path + img + on;
}

This code is somehow producing the hanging images when moving the mouse over the 
menu really fast. It I replace it with this, more conventional, code:

path = "images/"
on = "_on.png"
off = "_off.png"
function switchimg(img, how)
{ if (how)
document.images[img].src = path + img + on
else document.images[img].src = path + img + off
}

then it works fine. Below are some links to the menu with the working script.

(Link to GIF version with new script)
http://www.xs4all.nl/~berendse/moztest/script/gif/menu.html
(Link to JPG version with new script)
http://www.xs4all.nl/~berendse/moztest/script/jpg/menu.html
(Link to PNG version with new script)
http://www.xs4all.nl/~berendse/moztest/script/png/menu.html

Comment 5

[K Chayka]

I am having a similar problem with "hanging" gif images at
http://www.vortxweb.net/ccs-pg/holidays/mz_aprilfool.shtml

The page has js functions for cursor trails (6 gifs that follow the cursor
around the screen).  99% of the time, the last image hangs in its initial
position near the top left corner of the page.  Occassionally, the last 2 will
hang, but usually it's just the last one.

Comment 6

[pnunn]

reassigning to a js person.
It doesn't appear to be a problem of decoding
or rendering the images.

Comment 7

[rogerl (gone)]

I ran a timing test on the JS code under 4.72 and a 3/23 optimized mozilla 
build. 
              4.72          Mozilla
indexOf()    26939           32265 
direct        6289           18391

(milliseconds for 1000000 iterations)

Comment 8

[Simon Lucy]

Could this be a race condition within the js interpreter? This is more than 
just a minor irritant, it makes any site that uses rollover likely to fail (in 
the sense that the page looks ****) using mozilla.

Comment 9

[Phil Schwartau]

Update: still problems on WinNT using Mozilla debug build made on 06/07/00.

1. Go to http://www.xs4all.nl/~berendse/moztest/png/menu.html with Mozilla.
MouseOvers that are horizontal seem to work OK. No matter how fast I move the  
mouse horizontally, the MouseOver events occur. But fast vertical mouse 
movements do not seem to produce the events consistently. 

In NN4.7 response was very good both for horizontal or vertical.
In IE4, horizontal movement fine, but vert movement showed occasional problems -
i.e. occasionally none of the events would occur; or only one which would "hang"


2. Go to http://www.vortxweb.net/ccs-pg/holidays/mz_aprilfool.shtml in Mozilla.
The "cursor trails" don't work very well. You only get a small number of them 
forming, and some of them "hang" ... 

In NN4.7 the trails work perfectly. They create quickly and decay properly.
In IE4, after a few seconds of mouse movement, I get script errors. The dialog 
box says: 

An error has occurred in the script on this page

Line: 137
Char: 3
Error: 'dom' is not an object
Code: 0

Line: 149
Char: 12
Error: 'dom' is not an object
Code: 0


NOTE: in Windows NT Task Manager, I monitored the CPU usage on this page: 

           NO MOUSE MOVEMENT             RAPID MOUSE MOVEMENT

NN4.7          0 - 7 %                         25 - 40 %
IE4            2 - 13%                         45 - 55 %
Moz            75-90% (!!!)                    100% 

CPU is at 75-90% when Moz is displaying this page, WITHOUT ANY MOUSE MOVEMENT!!! 
No messages are appearing in the debug console during this time. However, this 
leaves so little CPU to handle the cursor trails, no wonder they don't render 
well ! 

Comment 10

[Jeffrey Baker]

The reason it takes a while for the new image to be displayed is because the
image cahce is not working.  See bug 20110.  As for events getting wedged, I
have no idea.  If the events are really getting wedged, please update the
description on this bug.  If not, please mark this as duplicate of bug 20110.

Comment 11

[rogerl (gone)]

I'm not seeing any evidence that events are getting lost or (and in any case)
that the JS engine is responsible for the image delay. Dup'ing to 20110, but
feel free to re-open after that closes out and this is not fixed.

*** This bug has been marked as a duplicate of 20110 ***

Comment 12

[Stephen Walker]

verified. using the 2000092808 m18 nightly on win2k.