https://bugs.webkit.org/show_bug.cgi?id=100874

Patch by Hans Muller <hmuller@adobe.com> on 2012-11-08
Reviewed by Dirk Schulze.

Source/WebCore:

Revised the way that computeXIntersections() handles intersections with horizotal polygon edges.
Deciding if a vertex intersection corresponds to a polygon "edge crossing", i.e. a change from inside
to outside or outside to inside, now depends on which side of the horizontal line the function's
y parameter corresponds to. If the y corresponds to the top of the line, then isaMinY the parameter
is true, and an intersection with a horizontal edge is only considered to be an edge crossing if
if the inside of the polygon is just below the horizontal edge.  When isMinY is false then the inside
of the polygon must be just above the horizontal edge.

Tests: fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-003.html
       fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-004.html

* rendering/ExclusionPolygon.cpp:
(WebCore::getVertexIntersectionVertices): Corrected two cases where the next/previous vertex was determined incorrectly.
(WebCore::ExclusionPolygon::computeXIntersections): Added a bool isMinY parameter which specifies if the y parameter corresponds to the top or bottom a horizontal line.
(WebCore::ExclusionPolygon::getExcludedIntervals): Added the new computeXIntersections() parameter.
(WebCore::ExclusionPolygon::getIncludedIntervals): Ditto.
* rendering/ExclusionPolygon.h:
(WebCore::ExclusionPolygonEdge::previousEdge): Corrected the previousEdge() function.

LayoutTests:

Added two additional tests for rectilinear polygons, where the tops and bottoms
of lines intersect the polygons' horizontal edges. More tests of this kind will
be needed when exclusion layout supports polygons that break horizontal lines up
into more than one segment.

* fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-003-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-003.html: Added.
* fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-004-expected.html: Added.
* fast/exclusions/shape-inside/shape-inside-rectilinear-polygon-004.html: Added.

git-svn-id: http://svn.webkit.org/repository/webkit/trunk@133968 268f45cc-cd09-0410-ab3c-d52691b4dbfc