55976 - animated gif loads, then disappears

Status: VERIFIED FIXED

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

Description

[Jacob Kjome]

bug viewed in 2000101008 Mtrunk  Win32

When loading an animated gif from the stated URL, it loads, but then disappears
leaving only the alt text in its place.

Steps to reproduce:
1. load url http://www.fringeware.com/~melba/russ.html

2. Watch the "Brother Russell Ministries" animated gif (hint: cross is moving)

expected: gif loads and stays there

actual: gif loads momentarily, then the page reflows and the image disappears
leaving only the alt text


I'm attaching a simplified testcase which includes both the animated gif and
another static gif.  The static gif has no problem but the animated one disappears.

NOTE: It seemed to happen more readily when I moused over the image, however
given at least 10 - 15 seconds of waiting, it usually happens without mouse
interaction.

Jake

Comment 1

[Jacob Kjome]

Attachment: simplified testcase showing animated gif disappearing

Comment 2

[Andrew Sayman]

On Windows 98 SE 2000101008 I'm not seeing the gif disappear. After the page
finishes loading, the image does begin to jump however. It doesn't seem to jump
at the same point in the animation each time either. 

Comment 3

[Keyser Sose]

Seeing the jumping to marking as NEW.

Platform: PC
Os: Windows 98
Build #: 2000101014 Trunk Build M18

Comment 4

[Jacob Kjome]

It is strange that this would act different on Win2k and Win98??? I still see
the image load, but then disappear leaving only the alt text on build 2000101014
M18 on Win2k.

BTW, what is the difference between M18 builds and MTrunk builds??? They seem to
be interchangeable???

Jake

Comment 5

[pnunn]

I only see the problem on brother russel (branim.gif).

Each frame of the animation is specified as a interleaved image.
And the delay between frames is set to zero. We don't have enough
time between the first interlaced frame drawing and the second 
frame drawing. You see the first frame drawn lowrez and then the
2 frame shows up. This creates the 'jump'.

I'll attach 2 versions of the gif, one where interlacing is turned
off, the other has a 3/10 second delay between the frames.

Later I see if I can find a way to recognize when interlacing is more
of a problem than a help for slow connections and slow image display. 
-pn

Comment 6

[pnunn]

Attachment: gif with no interlacing on each frame

Comment 7

[pnunn]

Attachment: gif with 3/10 second delay between frames

Comment 8

[ajbu]

Note: The URL in the URL field and the attachment 16673 [details] are no longer valid.

Most (if not all) Animated Gif problems I came across so far are caused by a 
small display time. Small display times or display time=0 (other Animated Gif 
editors might use a 'delay time' setting) are causing high CPU usage, 
slow/flickering animations and images disappearing. This seems to depend most 
on the CPU speed of the viewer, and display settings (resolution /color depth).

As a 'work around' Internet Explorer does not use display times <= 5/100th 
second, and sets the display time of a frame to 10/100sec when smaller or equal 
to 5/100th sec.
So an animated gif with frames having a display time of 6/100th is actually 
running faster then a gif with frames having a 5/100th display time.

It might be good for Mozilla performance to do something similar, catching to 
small display times. Those animated gifs might cause problems on some computers 
otherwise, and are most likely not intended to run that fast anyway. (optimized 
for IE, or having a display time of 0).

I'll add an attachment with small images of frame times ranging from 0 to 
10/100th second. it is MHTML format(Html with Mime encoded images), you should 
be able to drop it into IE/Mozilla/NS 4.x

Comment 9

[ajbu]

Attachment: testcase. page with animated gifs from 0 to 10/100th second display time. (MHTML format, can be dropped in Mozilla)

Comment 10

[pnunn]

All pnunn bugs reassigned to Pav, who is taking over
the imglib.

Comment 11

[Terri Preston]

This appears to be fixed by the new imagelib, verified this on w2k build 
2001040404

Comment 12

[Terri Preston]

Verified fixed w2k 2001081003