417246 - In FF3 the top border of an element is rendered with a smaller height if: * the DIV is empty and * border-top-style is not (dotted or dashed) and border-bottom-style is (dotted or dashed) and * border-top-width is greater than border-bottom-width

Status: RESOLVED FIXED

(Core :: Layout, defect, P2)

Description

[Dan POPA]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b4pre) Gecko/2008021204 Minefield/3.0b4pre
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9b4pre) Gecko/2008021204 Minefield/3.0b4pre ID:2008021204

In FF3 the top border of an element is rendered with a smaller height if: * the DIV is empty and * border-top-style is not (dotted or dashed) and border-bottom-style is (dotted or dashed) and * border-top-width is greater than border-bottom-width. See attachment.

Reproducible: Always

Comment 1

[Dan POPA]

See attachment 303034 [details] for bug 379303

Comment 2

[Dan POPA]

This does not reproduce on FF2.

Comment 3

[dolphinling]

I see this on linux, too.

Comment 4

[David Baron :dbaron: (⌚️UTC-4, no longer working on Mozilla)]

How about steps to reproduce?

Comment 5

[Dan POPA]

See attachment 303034 [details] of the bug 379303
You can change the top and bottom border styles and widths to see the bug in action. You can trigger the bug with any combination of the border styles marked with a red background.

 
In FF3:

    * create an empty DIV
 and
    * set border-top-style other than (dotted or dashed) and border-bottom-style to (dotted or dashed)
 and
    * set border-top-width to a value s greater than the border-bottom-width

Actual results: the top border is rendered with a smaller width than specified.


Use the following css for any empty DIV (or other tag):
{
  background-color: red; /*so we can see the background*/
  border-top: 30px solid lime;
  border-bottom: 10px dashed blue;
} 

Results:
- the top border should be 30px all but instead it appears to be 20px
- the red background can be seen through what should have been the lower 10px of the top border
- the bottom border appears solid instead of dashed.

Comment 6

[Dan POPA]

This may be same as bug 417543

Comment 7

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

Attachment: an actual testcase

Comment 8

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

This is almost certainly a regression from Vlad's border work. Shouldn't be hard to fix and I think we should fix it.

Comment 9

[Dan POPA]

(In reply to comment #7)
> Created an attachment (id=306423) [details]
> an actual testcase
> 

Could use attachment 303034 [details] of the bug 379303

Comment 10

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

It's much better to have a very simple testcase than a rather complex dynamic testcase.

Comment 11

[Dan POPA]

That's true only if the testcase covers all the possible combinations, as described in the bug description. Your testcase covers only one.

It's true, the developer may need to verify his code against only one case, but I really tried to make sure he get it right in all cases.

Comment 12

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

If you want to test a lot of cases, make a set of testcases, or one testcase that contains a lot of elements that test the different cases. Asking people to click on a lot of options to test everything is not helpful.

Comment 13

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

So the problem is this code here:

http://mxr.mozilla.org/seamonkey/source/layout/base/nsCSSRendering.cpp#1121

The way rendering with dotted bits work is we first render the corners, and then we go back and fill in the sides.  This is done to avoid weird discontinuities at the corners when using dotted/dashed borders, especially with rounded borders.  The problem in this case is that there really aren't any corners.  But this halfWidth/halfHeight stuff, I can't remember what that was protecting against.  Removing the halfWidth/halfHeight clamping fixes the problem, and I don't see anything wrong with any of my testcases.  Running reftests now.

Comment 14

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Attachment: get rid of bogus check

Reftests say everything's ok, so let's get rid of that code.

Comment 15

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

So what happens now if you have a very small DIV with very large border-radius?

Comment 16

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

Nothing different; the radii are already clamped at http://mxr.mozilla.org/seamonkey/source/layout/base/nsCSSRendering.cpp#2259 .

Comment 17

[Vladimir Vukicevic [:vlad] [:vladv] (needinfo me, slow to respond)]

checked in, along with the reftests.