292914 - No repaint after scrolling 32768 pixels

Status: RESOLVED FIXED

(Core :: Web Painting, defect)

Description

[Sébastien Desvignes]

User-Agent:       Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b2) Gecko/20050504
Build Identifier: Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b2) Gecko/20050504

Well I scroll to the bottom of the document using the <end> key, I sometime see
other parts of the document. It is a repaint problem, because the links are
still active, and the mouse pointer change when I hover them (even if I can't
see them because they are not drawn)
Scrolling with page down or the scroll bar doesn't show the bug.

Reproducible: Sometimes

Steps to Reproduce:
1. Open a long page, see URL for example
2. Scroll to bottom using the <end> key
3. If the bug doesn't show, go to the top again, and scroll with the <Page down>
key one time and repeat step 2

Actual Results:  
Parts of the top of the page is displayed instead of the bottom.

Expected Results:  
Display the good part of the page

Tested with Mozilla and Firefox

Comment 1

[Sébastien Desvignes]

Attachment: Screenshot showing the problem

Comment 2

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

Is this Mac only? I don't see other reports.

WHen did this regress?

Comment 3

[Sébastien Desvignes]

I think it is Mac only, but I can't be sure.
I'm testing the 2005042110 build now, and the bug is present.
In fact, the bug is not really easy to reproduce in normal browsing, so it can
stay unnoticed.
I have seen the bug only with the bug page in the URL, and the steps have
changed a little. I need to <page down> x5, then <end> to trigger the bug now.
It seems that to trigger the bug, the page must be long enough, and you need to
scroll with a certain amount of pixel in one time (but not too much).

Comment 4

[Sébastien Desvignes]

Ah ah !
I found something to reproduce the bug easily !
1. Open the page in the URL field
2. enter 'javascript:window.scrollTo(0,32768)' in the location field (or use a
bookmarklet)
3. the display don't change

Comment 5

[Sébastien Desvignes]

It seems to be an old problem, I've reproduced the bug with Firefox 1.0.2 (using
the javascript:scrollTo)
A friend with a Linux box said that there is no bug for him, so I think it is
Mac specific.

Comment 6

[Jesse Ruderman]

I ran into a similar bug while using Find on a Bonsai page and made a testcase.
 Comment 4 makes me believe my bug is the same as this one.

Comment 7

[Jesse Ruderman]

Attachment: testcase

To reproduce, load this testcase and press End and then Home.  Another way to
reproduce is to load the testcase, use Find for the string 'o', and Find Again
until it wraps.

I've seen this problem while scrolling down similar distances, but this
testcase only shows the problem while scrolling up.

Comment 8

[Jesse Ruderman]

Btw, I'm testing with trunk:
Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b4) Gecko/20050715
Firefox/1.0+

Comment 9

[Simon Fraser [no longer active]]

QuickDraw uses 16-bit coordinates which max out at 32767.

Comment 10

[Simon Fraser [no longer active]]

Attachment: Patch: bypass ScrollWindowRect for full-widget scrolls

This patch bypasses ScrollWindowRect if we're scrolling by an amount that is
equal to or more than the height or width of the rect to be scrolled; in this
case, we just invalidate the rect. This seems to work around a bug where
ScrollWindowRect() fails to invalidate when the amount scrolled approaches the
signed 16-bit limit.

Comment 11

[Simon Fraser [no longer active]]

diff is -w; I detabbed the method.

Comment 12

[Simon Fraser [no longer active]]

Checked in.

Comment 13

[Greg Tiller]

(In reply to comment #12)
> Checked in.

There is still a repaint bug present if you view an applet and then hit back the
area under the applet frame is not repainted.

Comment 14

[Simon Fraser [no longer active]]

(In reply to comment #13)
> There is still a repaint bug present if you view an applet and then hit back the
> area under the applet frame is not repainted.

Does that have anything to do with scrolling? Sounds like bug 277067.