[CSS Shapes] Simplify Polygon implementation

[CSS Shapes] Simplify Polygon implementation

Only floats can specify shape-outside. For polygon shape-outside values, the problem
of finding the left and right exclusion edges reduces to finding the X axis
limits of the polygon edges that overlap a particular layout line. This is a much
simpler version of the problem that PolygonShape was originally designed for, and so
the implementation can also be simplified. There's more about the new algorithm in
http://hansmuller-webkit.blogspot.com/2014/03/a-simpler-algorithm-for-css-shapes.html.

This is a merge of http://trac.webkit.org/changeset/166790 by Hans Muller <hmuller@adobe.com>;.

BUG=360139
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170931

[rwlbuis, 2014-04-04 20:32:02]

PTAL :)

[Stephen Chennney, 2014-04-04 20:42:35]

I haven't looked at the rest of the code, but I'm not happy with the FloatRect
changes.

https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
File Source/platform/geometry/FloatRect.h (right):

https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
Source/platform/geometry/FloatRect.h:145: bool overlapsYRange(float y1, float
y2) const { return !isEmpty() && y2 >= y1 && y2 >= y() && y1 <= maxY(); }
I don't think this should be in FloatRect.

It's checking facts about the range (y2 >= y1) in addition to the rect
comparison, and it's only used in the code you're changing. If you can find
other users of the same functionality then modify them too, otherwise put this
in the shapes code.

https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
Source/platform/geometry/FloatRect.h:146: bool overlapsXRange(float x1, float
x2) const { return !isEmpty() && x2 >= x1 && x2 >= x() && x1 <= maxX(); }
Ditto.

[rwlbuis, 2014-04-04 21:44:34]

On 2014/04/04 20:42:35, Stephen Chenney wrote:
> I haven't looked at the rest of the code, but I'm not happy with the FloatRect
> changes.
> 
>
https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
> File Source/platform/geometry/FloatRect.h (right):
> 
>
https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
> Source/platform/geometry/FloatRect.h:145: bool overlapsYRange(float y1, float
> y2) const { return !isEmpty() && y2 >= y1 && y2 >= y() && y1 <= maxY(); }
> I don't think this should be in FloatRect.
> 
> It's checking facts about the range (y2 >= y1) in addition to the rect
> comparison, and it's only used in the code you're changing. If you can find
> other users of the same functionality then modify them too, otherwise put this
> in the shapes code.
> 
>
https://codereview.chromium.org/226363003/diff/1/Source/platform/geometry/Flo...
> Source/platform/geometry/FloatRect.h:146: bool overlapsXRange(float x1, float
> x2) const { return !isEmpty() && x2 >= x1 && x2 >= x() && x1 <= maxX(); }
> Ditto.

Fair enough, I moved it to PolygonShape.cpp now.

[Hans Muller, 2014-04-04 21:54:32]

The changes look good to me.

[rwlbuis, 2014-04-04 22:07:00]

Another code simplification patch ported over from WebKit.

[eseidel, 2014-04-05 01:49:04]

lgtm

https://codereview.chromium.org/226363003/diff/20001/Source/core/rendering/sh...
File Source/core/rendering/shapes/PolygonShape.h (right):

https://codereview.chromium.org/226363003/diff/20001/Source/core/rendering/sh...
Source/core/rendering/shapes/PolygonShape.h:50: bool isWithinYRange(float y1,
float y2) const { return y1 <= minY() && y2 >= maxY(); }
One of these years we'll need a FloatRange or FloatInterval class.  Would make
this kind of thing simpler.

[rwlbuis, 2014-04-05 02:56:46]

The CQ bit was checked by rob.buis@samsung.com

[commit-bot: I haz the power, 2014-04-05 02:56:51]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/rob.buis@samsung.com/226363003/20001

[commit-bot: I haz the power, 2014-04-05 21:47:14]

Change committed as 170931