Closed Bug 171282 Opened 22 years ago Closed 3 months ago

Single-pixel rendering error when scrolling with non 96DPI setting


(Core Graveyard :: GFX, defect, P2)



(Not tracked)



(Reporter: kmcclusk, Assigned: kmcclusk)




(Keywords: polish)

This bug was broken off from

There is a single pixel scrolling error when is scrolled.
Blocks: 80530
Priority: -- → P2
Target Milestone: --- → Future
Blocks: 63336
No longer blocks: 80530
The actual bug condition seems to be DPI not be an integral divisor of 1440.
In other words, 1440/DPI must be an integer.
Contrary to the previous bug, the scrolling error now also seem to occur in the
middle of a text line, where as far as I have seen it only occured at the
topmost pixelline before.

I see it on Win2k Moz1.2a as well.
I still see this with Mozilla 1.2b under RedHat Linux 8.0. This bug is why I
keep sticking with Mozilla 1.0.1+(a patch that fixes all the off by one pixel
errors for 1.0.x).

This bug is very visible on  but only with certain
font settings. If you set the sans-serif font to TTF Microsoft Verdana with a
default size of 18 pixels, almost every 3rd line of text gets corrupted when
scrolling. This seems to be independent of the display resolution chosen in the
Mozilla prefs. My "real" screen resolution is 89 dpi (that's what xdpyinfo
says). Using Linux build 2002110321.
This bug is still happening with Mozilla 1.3.

It is very annoying.  Will it be going away any time soon?

I see it on two machines, one at 108x108 DPI, the other at 75x75 DPI.

Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.3) Gecko/20030314
Linux 2.4.9-13smp #1 SMP Tue Oct 30 19:06:50 EST 2001 i686 unknown
mozilla-1.3-0_rh7.i386.rpm from

*** Bug 190255 has been marked as a duplicate of this bug. ***
I think I'm seeing exactly this bug with Mozilla 1.3 although I have 96dpi
resolution set in Mozilla. And when I use the text zoom feature it appears even
more often.
Keywords: polish
This looks like the same problem as bug #94739.

Changing font, font size, DPI or text zoom fixes the problem for certain
HTML pages, but not for all. Personally, I can drastically reduce the effect
of missing horizontal pixel lines by changing text zoom manually to 99%.
However, this doesn't really help as this setting is not saved (every new
tab/window has again 100%).

Looks like it also depends on graphics card and display (no problem on
Nvidia with 17" TFT, but heavy problems on Radeon with 18" TFT). It's not
only in Mozilla but also in Firebird 0.6 (the "new" stand-alone browser),
so it looks like a general problem of the Gecko rendering engine (or how
it deals with glib/gtk library).

Btw, this bug is not Linux or Hardware related. It has been seen
on various platforms (see #94739).

The bug is also not related to non-96 dpi. I can reproduce it even
with 96 dpi.
This is dupe of bug #94739, I think also...
Blocks: 134942
*** Bug 217753 has been marked as a duplicate of this bug. ***
Istn't this a duplicate of bug 152671?
Is this still an issue after Eli's unit fix? (I can't check due to my Linux machine being broken.)
Mozilla/5.0 (OS/2; U; Warp 4.5; en-US; rv: Gecko/20070721

Yes, I still see the occasional off-by-one in the middle of a text line while scrolling. It is always missing a scan line. Placing the cursor on the line causes a repaint which fixes the display.
Could you test it with a Trunk build (1.9)? (Firefox is a bit too old to test.
Any response? We need to confirm this in the current trunk or the Firefox 3 beta. (I think this is now gone thanks to the unit fix.)
Product: Core → Core Graveyard
Closed: 3 months ago
Resolution: --- → INCOMPLETE
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