304004 - contents of button not renderer equally when using style:position:absolute;

Status: RESOLVED FIXED

(Core :: Layout: Form Controls, defect)

Description

[Egon Knapen]

User-Agent:       Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b4) Gecko/20050807 Firefox/1.0+
Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8b4) Gecko/20050807 Firefox/1.0+

Following two lines, produce different results:

<input type=button value="hello" style="width:40px;"><br>
<input type=button value="hello" style="width:40px; position:absolute;">

It seems when using position:absolute; an extra padding is added.

Reproducible: Always

Steps to Reproduce:
1. just put two lines above in an html page
2.
3.
Actual Results:  
the first 'hello' is renderer in the center of the button
the second 'hello' is renderer as if there is a padding of around 5px to the left.

Expected Results:  
the second button should have been renderer just the same as the first one.

The following removes the extra padding effect

<input type=button value="hello" style="width:40px; position:absolute;
padding:0px;">

But the question is still, where does that extra padding come from.

Comment 1

[Martijn Wargers (dead)]

Attachment: testcase

This testcase is not really concise, but it does show (at least to me) that the
default rendering (without position:absolute) seems to be something special in
some way. I can't reproduce such a thing with normal css and <div>'s.
Maybe this code has got something to do with it:
http://bonsai.mozilla.org/cvsblame.cgi?file=mozilla/layout/forms/nsHTMLButtonControlFrame.cpp&rev=3.191&root=/cvsroot#535

Comment 2

[Boris Zbarsky [:bzbarsky]]

What's happening here is that our internal block is not shrink-wrap for cases when the button is a block (as here, when it's positioned).  And that repositioning hack only kicks in for cases when the internal block is shrink-wrap (so only for inline buttons).

Not sure offhand what we can do about that... :(

Comment 3

[Boris Zbarsky [:bzbarsky]]

Although frankly, why are we only doing this for inlines?  Block-level buttons lay out pretty much the same way, from what I can tell...

Comment 4

[Boris Zbarsky [:bzbarsky]]

Attachment: Proposed change

I did some digging around to see why the code is this way, and came on some totally commentless kipp checkins... I don't see why we want this behavior difference, frankly.

Comment 5

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

Comment on attachment 203970 [details] [diff] [review]
Proposed change

This is the stuff that's going to make finishing the reflow branch so much fun.

Comment 6

[Boris Zbarsky [:bzbarsky]]

Fixed

Comment 7

[Martijn Wargers (dead)]

Verified with the testcase, using:
Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9a1) Gecko/20051124 Firefox/1.6a1

Thanks, Boris!