477552 - Zooming on planet.ubuntu.com creates weird gray lines

Status: RESOLVED DUPLICATE of bug 468496

(Core :: Layout, defect, P3)

Description

[Daniel Holbert [:dholbert]]

Attachment: screenshot of bug on planet.ubuntu.com

STR:
 1. Visit http://planet.ubuntu.com/
 2. Zoom out (Ctrl -)

ACTUAL RESULTS:  Weird gray lines appear in various places (see screenshot)
EXPECTED RESULTS: No weird gray lines.

Broken on mozilla-central and 1.9.1 branch.  Tested these builds:
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2a1pre) Gecko/20090208 Minefield/3.2a1pre
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1b3pre) Gecko/20090203 Shiretoko/3.1b3pre

But, working in Firefox 3.0.5:
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.5) Gecko/2008121622 Ubuntu/8.10 (intrepid) Firefox/3.0.5

Requesting blocking status, as this is a regression in 3.1 with respect to 3.0.

Comment 1

[Daniel Holbert [:dholbert]]

FWIW, I get gray lines when zooming in, too.

Almost all zoomlevels (aside from 1.0x) give me weird gray lines *somewhere*, though the lines' location varies depending on the zoomlevel.

Comment 2

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Linux only? Seems to WFM on Mac.

Definitely need a regression window and a reduced testcase.

Comment 3

[Zack Weinberg (:zwol)]

Attachment: reduced test case

I see it on Linux & I'm willing to bet it's bug 468496 (i.e. yet another place where it matters that we aren't using CAIRO_EXTEND_PAD).  Reduced self-contained test case attached.  (One of) the problem images is embedded; it'll be at the far right of the window.  Scale the page up and down and you should see gray or black lines at its edges.

Comment 4

[Daniel Holbert [:dholbert]]

Attachment: testcase 1

On planet.ubuntu.com, it seems the gray lines appear on the edges of of the "chat bubble" PNG images, which are displayed via the CSS "background:" property.

Here's a reduced testcase, using a mozilla PNG image to display the same problem.  I see gray or black lines on the bottom & right edges of the 300x300 div in this testcase at these zoomlevels:
  Zoomed out 1x
  Zoomed out 7x (that's the max that it lets you zoom out, btw)

  Zoomed in 3x
  Zoomed in 13x

(where "zoomed out/in [N]x" means to start at default zoomlevel, hold ctrl, and press - or + N times)

Comment 5

[Zack Weinberg (:zwol)]

Yup, I can see lines at the bottom & right edges of the image on my computer too, but at different zoomlevels:

  zoomed out 1x (gray)
  zoomed out 3x (black)
  zoomed out 5x (black) (it won't let me zoom out any farther than this)

  zoomed in 3x, 13x (black) (*only if* zooming is done with the scroll wheel, not with Ctrl-+ -- it looks like Ctrl-+ takes bigger steps)

Comment 6

[Daniel Holbert [:dholbert]]

(In reply to comment #5)
>   zoomed in 3x, 13x (black) (*only if* zooming is done with the scroll wheel,

Oh, sorry -- I was in fact using the scroll wheel when making my counts in comment 4. :)  I assumed the steps were the same, but I guess they aren't.

Comment 7

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Should be able to test the EXTEND_PAD hypothesis by hacking it in and seeing what happens, assuming EXTEND_PAD actually works on your system...

Comment 8

[Zack Weinberg (:zwol)]

Attachment: demo that EXTEND_PAD solves the problem

Indeed, the attached patch makes the problem disappear for me on both test cases and on planet.ubuntu.com.  However, it is also visibly very slow.

Comment 9

[Zack Weinberg (:zwol)]

Comment on attachment 361449 [details] [diff] [review]
demo that EXTEND_PAD solves the problem

clarifying title.  ALso, please ignore the changes to reftests/border-image/reftest.list in the patch, I forgot I had some other changes in my tree.

Comment 10

[Robert O'Callahan (:roc) (email my personal email if necessary)]

I'd still like to know the regression range, but I suspect this is going to end up in the "X drivers suck" department.

Comment 11

[Zack Weinberg (:zwol)]

I have an idea, which I shall describe in bug 468496 later.  Need to finish up some other stuff first.

Comment 12

[Daniel Holbert [:dholbert]]

FWIW: I can actually reproduce the bug by viewing a PNG image directly (e.g. http://www.mozilla.org/images/front-moz-store.png ) and then simply zooming that.  No need to use "background: url()" after all.

Comment 13

[Daniel Holbert [:dholbert]]

Related to bug 467832?

Comment 14

[Sylvain Pasche]

Same regression range as bug 487996 (probable fallout from bug 458487).

Comment 17

[Robert O'Callahan (:roc) (email my personal email if necessary)]

Duplicate of bug 468496 indicated by comment #8.