Add base types for path ops

Paths contain lines, quads, and cubics, which are
collectively curves.

To work with path intersections, intermediary curves
are constructed. For now, those intermediates use
doubles to guarantee sufficient precision.

The DVector, DPoint, DLine, DQuad, and DCubic
structs encapsulate these intermediate curves.

The DRect and DTriangle structs are created to
describe intersectable areas of interest.

The Bounds struct inherits from SkRect to create
a SkScalar-based rectangle that intersects shared
edges.

This also includes common math equalities and
debugging that the remainder of path ops builds on,
as well as a temporary top-level interface in
include/pathops/SkPathOps.h.
Review URL: https://codereview.chromium.org/12827020

git-svn-id: http://skia.googlecode.com/svn/trunk@8551 2bbb7eff-a529-9590-31e7-b0007b416f81

1 files changed, 135 insertions, 0 deletions

diff --git a/src/pathops/SkIntersectionHelper.h b/src/pathops/SkIntersectionHelper.h
new file mode 100644
index 0000000000..5d8ebcd590
--- /dev/null
+++ b/src/pathops/SkIntersectionHelper.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright 2012 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#include "SkOpContour.h"
+#include "SkPath.h"
+
+class SkIntersectionHelper {
+public:
+    enum SegmentType {
+        kHorizontalLine_Segment = -1,
+        kVerticalLine_Segment = 0,
+        kLine_Segment = SkPath::kLine_Verb,
+        kQuad_Segment = SkPath::kQuad_Verb,
+        kCubic_Segment = SkPath::kCubic_Verb,
+    };
+
+    void addCoincident(SkIntersectionHelper& other, const SkIntersections& ts, bool swap) {
+        fContour->addCoincident(fIndex, other.fContour, other.fIndex, ts, swap);
+    }
+
+    // FIXME: does it make sense to write otherIndex now if we're going to
+    // fix it up later?
+    void addOtherT(int index, double otherT, int otherIndex) {
+        fContour->addOtherT(fIndex, index, otherT, otherIndex);
+    }
+
+    // Avoid collapsing t values that are close to the same since
+    // we walk ts to describe consecutive intersections. Since a pair of ts can
+    // be nearly equal, any problems caused by this should be taken care
+    // of later.
+    // On the edge or out of range values are negative; add 2 to get end
+    int addT(const SkIntersectionHelper& other, const SkPoint& pt, double newT) {
+        return fContour->addT(fIndex, other.fContour, other.fIndex, pt, newT);
+    }
+
+    int addSelfT(const SkIntersectionHelper& other, const SkPoint& pt, double newT) {
+        return fContour->addSelfT(fIndex, other.fContour, other.fIndex, pt, newT);
+    }
+
+    int addUnsortableT(const SkIntersectionHelper& other, bool start, const SkPoint& pt,
+                       double newT) {
+        return fContour->addUnsortableT(fIndex, other.fContour, other.fIndex, start, pt, newT);
+    }
+
+    bool advance() {
+        return ++fIndex < fLast;
+    }
+
+    SkScalar bottom() const {
+        return bounds().fBottom;
+    }
+
+    const SkPathOpsBounds& bounds() const {
+        return fContour->segments()[fIndex].bounds();
+    }
+
+    void init(SkOpContour* contour) {
+        fContour = contour;
+        fIndex = 0;
+        fLast = contour->segments().count();
+    }
+
+    bool isAdjacent(const SkIntersectionHelper& next) {
+        return fContour == next.fContour && fIndex + 1 == next.fIndex;
+    }
+
+    bool isFirstLast(const SkIntersectionHelper& next) {
+        return fContour == next.fContour && fIndex == 0
+                && next.fIndex == fLast - 1;
+    }
+
+    SkScalar left() const {
+        return bounds().fLeft;
+    }
+
+    const SkPoint* pts() const {
+        return fContour->segments()[fIndex].pts();
+    }
+
+    SkScalar right() const {
+        return bounds().fRight;
+    }
+
+    SegmentType segmentType() const {
+        const SkOpSegment& segment = fContour->segments()[fIndex];
+        SegmentType type = (SegmentType) segment.verb();
+        if (type != kLine_Segment) {
+            return type;
+        }
+        if (segment.isHorizontal()) {
+            return kHorizontalLine_Segment;
+        }
+        if (segment.isVertical()) {
+            return kVerticalLine_Segment;
+        }
+        return kLine_Segment;
+    }
+
+    bool startAfter(const SkIntersectionHelper& after) {
+        fIndex = after.fIndex;
+        return advance();
+    }
+
+    SkScalar top() const {
+        return bounds().fTop;
+    }
+
+    SkPath::Verb verb() const {
+        return fContour->segments()[fIndex].verb();
+    }
+
+    SkScalar x() const {
+        return bounds().fLeft;
+    }
+
+    bool xFlipped() const {
+        return x() != pts()[0].fX;
+    }
+
+    SkScalar y() const {
+        return bounds().fTop;
+    }
+
+    bool yFlipped() const {
+        return y() != pts()[0].fY;
+    }
+
+private:
+    SkOpContour* fContour;
+    int fIndex;
+    int fLast;
+};