https://bugs.webkit.org/show_bug.cgi?id=99343

Patch by Hans Muller <hmuller@adobe.com> on 2012-11-05
Reviewed by Dirk Schulze.

Source/WebCore:

ExclusionPolygonEdges now span coincident and collinear vertices. Currently
pairs of vertices are only considered coincident if their coordinates are exactly
equal. Similarly, a vertex is only considered collinear with an edge if the area
of the triangle defined by the three vertices is exactly zero.  In the future it
may be useful to relax the comparison with zero.

Tests: fast/exclusions/shape-inside/shape-inside-coincident-vertices.html
       fast/exclusions/shape-inside/shape-inside-collinear-vertices.html

* rendering/ExclusionPolygon.cpp:
(WebCore::determinant): Used to measure collinearity.
(WebCore):
(WebCore::areCollinearPoints): True if three FloatPoint arguments are collinear per the test outlined above.
(WebCore::areCoincidentPoints): True if the two FloatPoint arguments are equal.
(WebCore::nextVertexIndex): The next vertex index in clockwise or counterclockwise order.
(WebCore::ExclusionPolygon::findNextEdgeVertexIndex): Return the index of the next non-coincident, non-collinear vertex.
(WebCore::ExclusionPolygon::ExclusionPolygon): Skip coincident and collinear vertices when building the list of edges.
* rendering/ExclusionPolygon.h: Added private findNextEdgeVertexIndex() declaration.

LayoutTests:

Verify that exclusion polygonal shape-inside layout is unaffected by coincident
or collinear vertices.

* fast/exclusions/shape-inside/shape-inside-coincident-vertices-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-coincident-vertices.html: Added.
* fast/exclusions/shape-inside/shape-inside-collinear-vertices-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-collinear-vertices.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@133490 268f45cc-cd09-0410-ab3c-d52691b4dbfc