83786 - Table width algorithm ignores right margin (and uses left margin instead) [MARGIN-H] (tables, margins)

Status: VERIFIED FIXED

(Core :: Layout: Tables, defect)

Description

[Hixie (not reading bugmail)]

When working out if a table fits in its container (and thus whether it should
be shrunk), we use the left margin instead of the right margin.

Thus, for example, in:

   table {
     margin-left: 1em;
     margin-right: 10em;
   }

...we assume that the table has horizontal margins of "2em" when trying to size
the table. Later, when we actually lay the table out and work out if we need
scroll bars, we correctly realise that the right margin is 10em.

This is visible in one of the testcases mentioned on bug 72060:
   http://web.thock.com/mozilla/css_bug2b.html
The table should have 10em right margin, but when being sized our code assumes 
that the table has 0 right margin (since the left margin is 0) and therefore
sizes the table to 100% (modulo borders). When we then lay this out, we see the
right margin and therefore provide a horizontal scrollbar.

This works fine when borders are used in the test instead of margins:
   http://www.hixie.ch/tests/adhoc/css/box/table/005.html

Comment 1

[Bernd]

steeling the bug; the following patch fixes the problem

Index: nsTableOuterFrame.cpp
===================================================================
RCS file: /cvsroot/mozilla/layout/html/table/src/nsTableOuterFrame.cpp,v
retrieving revision 3.191
diff -u -w -r3.191 nsTableOuterFrame.cpp
--- nsTableOuterFrame.cpp	2001/05/17 23:52:29	3.191
+++ nsTableOuterFrame.cpp	2001/06/04 16:35:08
@@ -521,7 +521,7 @@
   GetMarginPadding(aPresContext, aOuterRS, aChildFrame, marginIgnore,
aMarginNoAuto, aPadding);
   nscoord width = aOuterWidth;
   if (NS_UNCONSTRAINEDSIZE != width) {
-    width = aOuterWidth - aMarginNoAuto.left + aMarginNoAuto.right;
+    width = aOuterWidth - aMarginNoAuto.left - aMarginNoAuto.right;
     width = PR_MAX(width, mMinCaptionWidth);
   }
   return width;

Comment 2

[Bernd]

Attachment: patch

Comment 3

[Bernd]

despite the discouraging comments at http://www.hixie.ch/tests/adhoc/css/box/table
tables need some more love (e.g. testcases). The provided patch fixes hixies
testcase and improves the picture at
http://lxr.mozilla.org/mozilla/source/layout/html/tests/table/bugs/bug15247.html
where the margin at the right of the second and third nested table is removed.
(I like regression tests!!). Further it makes nsTableFrame.cpp more stringent
because it removes completely the reference to margins that should be handled in
the outer frame.

Comment 4

[Hixie (not reading bugmail)]

The patch certainly logically explains the effect I was seeing.

Bernd: The person to ask for tables test cases is [e-mail] (the QA
contact for this bug, incidentally). Feel free to cc me on any correspondence.

Comment 5

[karnaze (gone)]

r=karnaze.

Comment 6

[Marc Attinasi]

sr=attinasi

Comment 7

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

a=dbaron for trunk checkin on behalf of drivers

Comment 8

[Bernd]

fix checked in,

>The person to ask for tables test cases is [e-mail] (the QA
>contact for this bug, incidentally). Feel free to cc me on any correspondence.

I know, but I know how makes the best testcases in town :-)

Comment 9

[Amarendra Hanumanula]

 Works fine in recent builds.