261006 - Transparent PNG images display incorrectly.

Status: RESOLVED FIXED

(Firefox :: General, defect)

Description

[Larry Klug]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.0; rv:1.7.3) Gecko/20040913 Firefox/0.10
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.0; rv:1.7.3) Gecko/20040913 Firefox/0.10

Transparent PNG images appear to render the background improperly, rendering the
background as it appears in the 0,0 position regardless of the position of the
PNG on the page. The described behavior does NOT occur with the following versions:

Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.4b) Gecko/20030516 Mozilla
Firebird/0.6

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20030626 Firefox/0.9.1

Reproducible: Always
Steps to Reproduce:
1. Load the following example URL:
http://www.mozilla.org/start/1.0/demos/eagle-sun.html
2. Drag sun or bird images around page.
3. Observe the miscalculation of position of background through transparent PNG
images.

Actual Results:  
Observe the miscalculation of position of background through transparent PNG
images. Flashing and misplacement of the background appears consistently, and
seems to confuse the background of one transparent PNG with other PNGs on the page.

Expected Results:  
Properly calculate the position of the background relative to the position of
the transparent PNG image.

Comment 1

[Peter van der Woude [:Peter6]]

Mozilla/5.0 (Windows; U; Windows NT 5.0; en-US; rv:1.7.3) Gecko/20040921
Firefox/0.10

Confirming ->NEW

Comment 2

[Dan Brown]

I do not get quite the same result as above, if I drag the bird around, the
background image renders severely offset from where it should be on the page. 
It is often close to 0, 0 however.

Strange observance:
I've been looking at this as well and I'd like to add that for some reason if
you startup IE and start up the Sun Java Console from the Tools menu transparent
PNG images will display correctly until you shutdown both the Java console and
the IE window, at which point Firefox will once again display the images
incorrectly.

IE Version: 6.0.2800.1106
Java(TM) Plug-in: Version 1.4.2_04

Steps to reproduce:
1. Follow the bug steps for Firefox above.
2. Start IE, repeat steps 2-3 in bug report above
3. Load the 'Sun Java Console' from the Tools menu
4. Follow steps 2-3 in the original bug report, note that the PNG problem has
disappeared.


Will this help any?
Could be, might just be a red herring however.

Comment 3

[António Ferreira]

I experience the same problem with transparent PNGs on Firefox 1.0 Preview
release, on Win XP Home. When I load http://binarybonsai.com, a transparent PNG
renders with the background color of the html. When I open IE and load de Java
Console, I switch back to Firefox and the PNG is now displayed correctly.

Comment 4

[Colin S]

Confirmed Mozilla/5.0 (Windows; U; Windows NT 5.1; rv:1.7.3) Gecko/20040913
Firefox/0.10.1 on 2 separate systems. Unable to get symptoms to occur on the
system on which I am currently typing, which has Mozilla 1.7.3 installed and
used as the primary browser (Mozilla Suite never seems to have the problem).
In my opinion this should be marked as having Major severity. I'd love to have
it set as a 1.0 blocker, but of course it isn't. :)

Comment 5

[António Ferreira]

I managed to test without opening IE. I just opened the java console window from
the win xp (home edition with service pack 2 installed) control panel and the
png's displayed correctly. My computer at work runs winxp pro w/service pack 2
and firefox 1.0 Preview shows the PNG's correctly.

Comment 6

[Dan Allen]

I just tried the demo URL on Linux with Mozilla/5.0 (X11; U; Linux i686;
rv:1.7.3) Gecko/20040913 Firefox/0.10 and it seems to work as expected,
confirming that this is a Windows specific issue.

Comment 7

[Mark Rawling]

Interesting and decisive discoveries!!! 

This bug has been plaguing me for 12 months or so. It is very frustrating
because most others I know do not experience it. In my case it manifests as
corruption to firefox and thunderbird toolbar and tab images. I believe there
are many duplicate/related bugs filed on this. 

Another related issue is that moving the mouse between the panes in thunderbird
causes dramatic 100% cpu hammering. The mouse becomes impossibly jerky and the
whole application seems to slow to a crawl. Often when this happens the images
in the folder and message panes become corruptm, specifically all the
transparent backgrounds get messed up. It is just like the corruption of the
transparent backgrounds described in this bug. 

Some duplicate bugs talk about the possibility of nvidia drivers being involved.
I can now confirm that categorically. 

My machine at home and at work are both Dells with nvidia drivers, RIVA TNT2 to
be precise. I did some experimenting and found the following: If you go to the
driver troubleshooting panel (from desktop properties) and set the hardware
acceleration to full, then all of these problems will occur. If you back it down
one notch to the setting described as 

  "Disable cursor and bitmap acceleration. Use this setting to correct problems 
   with the mouse pointer, or to correct problems with corrupt images" 

then sure enough the problems go away. The image corruption is completely solved
and the jerkiness of the mouse motion in thunderbird seems to disappear too. I
strongly suspect thunderbird does a lot of unnecessary image redrawing when the
mouse moves between panes and this tickles this bug.

I have downloaded and built a debug thunderbird, but really it would be very
difficult for me to debug with zero knowledge of the code. I truly hope this
information is enough to get this very nasty bug nailed. Honestly, it has been
driving me absolutely crazy for ages - I kept saying release after release,
surely they have fixed this obvious and painful bug, but it never happened. I
guess noone at moz uses Dells with Rivas. Meanwhilw I will keep my hardware
acceleration notched back one and finally enjoy some relative peace of mind!!

Comment 8

[Mark Rawling]

More...

Inspired by these discoveries I just installed the latest nvidia driver (6693).
Problems solved! I have now gone back to full hardware acceleration. I assume
this is a real moz bug, since it only happens in moz apps, but the nvidia
drivers are also implicated, what that means exactly I'm not sure...

Oh, by the way, another way to see the bug is in the thunderbird options dialog
- the large left hand icons will have grey backgrounds instead of being
transparent when the problem is present.

Comment 9

[Colin S]

Confirmed that old nVidia drivers are the problem. I nominate WONTFIX INVALID.

Comment 10

[Dan Brown]

I have an NVidia card as well (TNT2 Model 64) and upgraded my drivers when I
checked on this bug yesterday.  After upgrading the drivers the problem has gone
away.  

Comment 11

[Larry Klug]

I do indeed have an nVidia card. RIVA TNT2. I will try updating the driver.

Comment 12

[Mark Rawling]

(In reply to comment #9)
> Confirmed that old nVidia drivers are the problem. I nominate WONTFIX INVALID.

I agree, but with this question in mind: How come it never happens in any other
Windows application? I'm concerned that moz images are in some sense not
hardware acceleration/driver friendly. Are we sure that moz is fully benefiting
from acceleration, etc, because I guarantee you that IE is...

Comment 13

[ViktorHorvath]

Attachment: testcase showing incorrect rendered semi-transparent PNG on coloured background. Gecko/20060110 on GNU/Linux.

While I can't confirm the problem in the original bug message, I do have problems with semi-transparent PNGs on GNU/Linux 2.6.13.2 i386 (latest Firefox in Debian unstable, Gecko/20060110) which changes the background color. I attach a very simple testcase for you which includes a tiny HTML file, an image and two screenshots, one of my Firefox and one of Konqueror 3.4.3 who behaves correctly.

I'm rather adding this here than creating a new bug - sorry if I'm wrong. For the record, I'm not using any modern nVidia card, but an old Matrox Millennium II one.

Comment 14

[ViktorHorvath]

I think I've got only problems with RGB semi-transparent PNG images, not indexed ones. HTH, Viktor.

Comment 15

[Michael Shamoon]

i have this problem on FF 2.0.0.1. The demo works fine for me though. Instead, in my case the png/gif has position:fixed styling, but has the same behavior of not re-rendering the transparent part of the image. However, in the most recent FF build, as of 2/17/07, this is fixed for me! yay.
can be seen at: http://g-fighter.com/blog_images/fffixeddemo.html

Comment 16

[Alfred Kayser]

Marking as fixed per comment #15.