Closed Bug 292914 Opened 19 years ago Closed 19 years ago

No repaint after scrolling 32768 pixels


(Core :: Web Painting, defect)

Not set





(Reporter: bob, Assigned: sfraser_bugs)




(Keywords: testcase)


(3 files)

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

WHen did this regress?
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).
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
3. the display don't change
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.
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.
Ever confirmed: true
Keywords: testcase
Summary: Repaint problem when scrolling to bottom of page → No repaint after scrolling 32768 pixels
Attached file 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.
Btw, I'm testing with trunk:
Mozilla/5.0 (Macintosh; U; PPC Mac OS X Mach-O; en-US; rv:1.8b4) Gecko/20050715
QuickDraw uses 16-bit coordinates which max out at 32767.
Assignee: roc → sfraser_bugs
Target Milestone: --- → mozilla1.8beta4
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.
Attachment #189643 - Flags: superreview?(jhpedemonte)
Attachment #189643 - Flags: review?(joshmoz)
diff is -w; I detabbed the method.
Attachment #189643 - Flags: superreview?(jhpedemonte) → review+
Attachment #189643 - Flags: review?(joshmoz) → review+
Attachment #189643 - Flags: approval1.8b4?
Attachment #189643 - Flags: approval1.8b4? → approval1.8b4+
Checked in.
Closed: 19 years ago
Resolution: --- → FIXED
(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.
(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.
Component: Layout: View Rendering → Layout: Web Painting
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