Rework SVG sizing

Source/core/css/svg.css

 /*
  * The default style sheet used to render SVG.
  *
  * Copyright (C) 2005, 2006 Apple Computer, Inc.  All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
@@ skipping 29 matching lines @@
     the initial clipping path is set according to the clipping rules as defined in [CSS2-overflow].
 
     Opera/Firefox & WebKit agreed on NOT setting "overflow: hidden" for the outermost svg element - SVG 1.1 Errata
     contains these changes as well as all future SVG specifications: see http://lists.w3.org/Archives/Public/public-svg-wg/2008JulSep/0347.html
 */
 
 svg:not(:root), symbol, image, marker, pattern, foreignObject {
     overflow: hidden
 }
 
+svg:root {
+    height: 100%;
+    width: 100%;
+    position: absolute

[pdr., 2014/04/15 02:46:10]

position: absolute seems odd to me. Can you talk a bit about why it's needed?

[davve, 2014/04/15 15:55:23]

I have this on my list of things to do. Current ramblings:

position: absolute is a bit of a hack to get the height percentage value to
resolve against the viewport dimensions. Could and should probably be replaced
with a corresponding "hack"/fix in the c++ code instead, somewhere in
RenderReplaced::hasReplacedLogicalHeight() or
RenderBoxModelObject::hasAutoHeightOrContainingBlockWithAutoHeight().

The RenderView (containing block of the root svg) has style height:auto, so we
need to avoid falling into turning height: 100% into height: auto in some way.
As for position:absolute, hasAutoHeightOrContainingBlockWithAutoHeight has a
check for isOutOfFlowPositioned() that makes us able to resolve the height to
the viewport (since position:absolute stuff is outside normal flow it doesn't
contribute to auto height ancestors thus it being safe to resolve it percentages
without loops).

I will continue to look into this.

[davve, 2014/04/16 14:35:30]

Addressed by allowing boxes to resolve percentages against the frame. See
RenderBoxModelObject::hasAutoHeightOrContainingBlockWithAutoHeight in patch set
14 and later.

+}
+
 text, foreignObject {
     display: block
 }
 
 text {
    white-space: nowrap
 }
 
 tspan, textPath {
    white-space: inherit
 }
 
 /* states */
 
 :focus {
     outline: auto 5px -webkit-focus-ring-color
 }
 
 /* CSS transform specification: "transform-origin 0 0 for SVG elements without associated CSS layout box, 50% 50% for all other elements". */
  
 * {
     -webkit-transform-origin: 0 0;
 }
 
 html|* > svg {
     -webkit-transform-origin: 50% 50%;
 }