[webkit-dev] Implementing CSS3 Paged Media Margin Boxes

Fri Apr 27 10:29:41 PDT 2012

On Friday 27 April 2012 10:08:13 Eric Seidel wrote:
> When I last looked at the page media stuff (long ago).  The problem
> was mostly going to be testing.  We don't have a good way to do
> printing tests right now in WebKit.

Someone in the webkit community introduced me to the idea of reftests, which 
seem to be a viable option for proper printing tests. I think of something 
like the following that should work since we know the pixel dimensions of a 
printed page in our unit tests to be 800x600:

// @page margin test
<html>
<head>
<style>
* { margin:0; padding:0; }
@page { margin: 10px; }
div {  width: 800px; height: 600px; background: green; }
</style>
</head>
<body>
<div>should have a 10px margin</div>
</body>
</head>
</html>

// alternative
<html>
<head>
<style>
* { margin:0; padding:0; }
div { width: 780px; height: 580px; margin: 10px; }
</style>
</head>
<body>
<div>should have a 10px margin</div>
</body>
</head>
</html>

Now both versions can be "printed" to PNG similar to what the existing 
LayoutTestController.setPrinting() does. The resulting two platform specific 
images can be compared and should match - if not, something went wrong.

Am I missing something, is the above impractical?

Cheers

> On Fri, Apr 27, 2012 at 7:22 AM, Milian Wolff <milian.wolff at kdab.com> wrote:
> > Hey all,
> > 
> > I would like to work on the CSS3 Paged Media support, esp. the margin
> > boxes. I'm studying the code for some time now and would welcome it if
> > someone could assist me in figuring out what needs to be done...
> > 
> > First up, I think I should tackle the missing support in the parser, i.e.
> > solving the FIXME in CSSParser::createMarginAtRule. I found that
> > CSSFontFaceRule looks similar and could write some code based on that. A
> > few questions arise now:
> > 
> > a) For the unit tests (probably not only there) I need to have a special
> > margin-at CSSRule for cssText(). I'll probably be able to copy most of the
> > stuff again, but where in the build system do I have to add these new
> > files?
> > 
> > b) What CSSRule::Type should the above have? WEBKIT_MARGINAT_RULE at the
> > end (hence value 11)?. I could not find an official IDL proposal that
> > includes the margin at rules.
> > 
> > c) These margin-at rules can only occur inside a page rule, and I need to
> > access them from somewhere - what is the suggested path to take here?
> > create StyleRulePage::setMarginRules or similar? Or reuse stuff from
> > StyleRuleBlock?
> > 
> > d) When I have some partial patch ready, where could I get input? Should I
> > attach it to a bug report (I've opened
> > https://bugs.webkit.org/show_bug.cgi?id=85062 for that purpose)
> > 
> > f) I see that there are files like JSCSSFontFaceRuleCustom.cpp - what do I
> > need to do there to get the new MediaAtRule accessible from JavaScript?
> > 
> > Bye
> > --
> > Milian Wolff | milian.wolff at kdab.com | Software Engineer
> > KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
> > Tel. Germany +49-30-521325470, Sweden (HQ) +46-563-540090
> > KDAB - Qt Experts - Platform-independent software solutions
> > 
> > _______________________________________________
> > webkit-dev mailing list
> > webkit-dev at lists.webkit.org
> > http://lists.webkit.org/mailman/listinfo.cgi/webkit-dev
-- 
Milian Wolff | milian.wolff at kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel. Germany +49-30-521325470, Sweden (HQ) +46-563-540090
KDAB - Qt Experts - Platform-independent software solutions
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