248799 - Vertical clipping of fonts

Status: RESOLVED EXPIRED

(Firefox :: General, defect)

Description

[Ciprian Popovici]

User-Agent:       Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040615 Firefox/0.9
Build Identifier: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.7) Gecko/20040615 Firefox/0.9

Fonts are sometimes "clipped", which means that their top is cut off and only
the lower part, to some extent, appears. Larger fonts are affected more often
small fonts. The clipping appears most often when scrolling pages by using the
scrollbar; when using the mouse scroll or keys it depends on how many lines they
are set to, too many lines (3+) won't produce clipping.

This is most easily noticed on the home page of The Register. I will attach a
screenshot. Aside from clipped headlines, also note the "Sun slams Red Hat"
headline, where only the hover is affected by the clipping.

Unfocusing the browser window or hiding it (changing window or desktop) will
magically make the fonts recover instantly. Selecting the affected fonts also
recovers them.

Reproducible: Always
Steps to Reproduce:
1. Go to http://theregister.co.uk/ or browse the CSS2 manual at W3C and scroll
using the scrollbar.
2. If the clipping doesn't occur, increase the zoom somewhat.
3. If the clipping still doesn't occur, try changing the fonts resolution in
Firefox (the natural one for my monitor is 83dpi, clipping kicks in badly at 92dpi).

Actual Results:  
Fonts have their upper half clipped off.

Expected Results:  
Display full lines of fonts.

Comment 1

[Ciprian Popovici]

Attachment: Screenshot showing the fonts clipping occur.

Comment 2

[Brent]

I see a similar problem in Mozilla in Linux (build 2004082100).  Mozilla 1.3 was
the last version that did not have this problem.  Regular sized text is clipped
by the top and bottom edge of the window when scrolled.  Larger text is not
affected.  If the window is repainted, the text is shown correctly.

Comment 3

[Brent]

Attachment: screenshot of clipped text in Mozilla 1.8a3, Linux

Comment 4

[Brent]

Larger text IS affected.  Just isn't as noticable when one row of pixels is
removed from a line in a larger font.  If one character is selected, the whole
element (up to one line) is repainted correctly.  Text above or below does not
move in response to a repaint of one line; the amount of space is correct.  When
a character is selected, the missing row of pixels is added and the rows of
pixels below the missing row shift down one pixel.

I am using Slackware 9.1.

Comment 5

[Patrick]

I am seing this too with FireFox 1.0 (Linux/Suse9.1/KDE3.3.1).

In an attempt to put things together, I am listing here bug reports that seem
related to me. Sorry for not doing more analysis (and reading all the comments
of all bugs listed here) or for the bugspam but I really think this linking
might be useful. Please note that this bug is listed too (as I put the same in
different bugs).

bug 172162 Linux
bug 174977 All (was Solaris)
bug 199840 Linux
bug 211704 Linux
bug 215759 Linux
bug 217336 Linux
bug 217825 All (was Linux)
bug 228808 MacOS X
bug 248799 Linux

I built this list by searching for scroll and font in the comments from newest
to oldest going up to the first one of this list (feel free to search further)
and I might have missed some.

I put the OS as it seems there is a link between them: is it due to the usage of
a common deployed library, a bug in an OS' library, ...?

Comment 6

[Gervase Markham [:gerv]]

This is an automated message, with ID "auto-resolve01".

This bug has had no comments for a long time. Statistically, we have found that
bug reports that have not been confirmed by a second user after three months are
highly unlikely to be the source of a fix to the code.

While your input is very important to us, our resources are limited and so we
are asking for your help in focussing our efforts. If you can still reproduce
this problem in the latest version of the product (see below for how to obtain a
copy) or, for feature requests, if it's not present in the latest version and
you still believe we should implement it, please visit the URL of this bug
(given at the top of this mail) and add a comment to that effect, giving more
reproduction information if you have it.

If it is not a problem any longer, you need take no action. If this bug is not
changed in any way in the next two weeks, it will be automatically resolved.
Thank you for your help in this matter.

The latest beta releases can be obtained from:
Firefox:     http://www.mozilla.org/projects/firefox/
Thunderbird: http://www.mozilla.org/products/thunderbird/releases/1.5beta1.html
Seamonkey:   http://www.mozilla.org/projects/seamonkey/

Comment 7

[Gervase Markham [:gerv]]

This bug has been automatically resolved after a period of inactivity (see above
comment). If anyone thinks this is incorrect, they should feel free to reopen it.