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, 148 insertions, 0 deletions

diff --git a/src/pathops/SkOpEdgeBuilder.cpp b/src/pathops/SkOpEdgeBuilder.cpp
new file mode 100644
index 0000000000..56e7c20043
--- /dev/null
+++ b/src/pathops/SkOpEdgeBuilder.cpp
@@ -0,0 +1,148 @@
+/*
+ * 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 "SkOpEdgeBuilder.h"
+#include "SkReduceOrder.h"
+
+void SkOpEdgeBuilder::init() {
+    fCurrentContour = NULL;
+    fOperand = false;
+    fXorMask[0] = fXorMask[1] = (fPath->getFillType() & 1) ? kEvenOdd_PathOpsMask
+            : kWinding_PathOpsMask;
+#if DEBUG_DUMP
+    gContourID = 0;
+    gSegmentID = 0;
+#endif
+    fSecondHalf = preFetch();
+}
+
+void SkOpEdgeBuilder::addOperand(const SkPath& path) {
+    SkASSERT(fPathVerbs.count() > 0 && fPathVerbs.end()[-1] == SkPath::kDone_Verb);
+    fPathVerbs.pop();
+    fPath = &path;
+    fXorMask[1] = (fPath->getFillType() & 1) ? kEvenOdd_PathOpsMask
+            : kWinding_PathOpsMask;
+    preFetch();
+}
+
+void SkOpEdgeBuilder::finish() {
+    walk();
+    complete();
+    if (fCurrentContour && !fCurrentContour->segments().count()) {
+        fContours.pop_back();
+    }
+    // correct pointers in contours since fReducePts may have moved as it grew
+    int cIndex = 0;
+    int extraCount = fExtra.count();
+    SkASSERT(extraCount == 0 || fExtra[0] == -1);
+    int eIndex = 0;
+    int rIndex = 0;
+    while (++eIndex < extraCount) {
+        int offset = fExtra[eIndex];
+        if (offset < 0) {
+            ++cIndex;
+            continue;
+        }
+        fCurrentContour = &fContours[cIndex];
+        rIndex += fCurrentContour->updateSegment(offset - 1,
+                &fReducePts[rIndex]);
+    }
+    fExtra.reset();  // we're done with this
+}
+
+// FIXME:remove once we can access path pts directly
+int SkOpEdgeBuilder::preFetch() {
+    SkPath::RawIter iter(*fPath);  // FIXME: access path directly when allowed
+    SkPoint pts[4];
+    SkPath::Verb verb;
+    do {
+        verb = iter.next(pts);
+        *fPathVerbs.append() = verb;
+        if (verb == SkPath::kMove_Verb) {
+            *fPathPts.append() = pts[0];
+        } else if (verb >= SkPath::kLine_Verb && verb <= SkPath::kCubic_Verb) {
+            fPathPts.append(verb, &pts[1]);
+        }
+    } while (verb != SkPath::kDone_Verb);
+    return fPathVerbs.count() - 1;
+}
+
+void SkOpEdgeBuilder::walk() {
+    SkPath::Verb reducedVerb;
+    uint8_t* verbPtr = fPathVerbs.begin();
+    uint8_t* endOfFirstHalf = &verbPtr[fSecondHalf];
+    const SkPoint* pointsPtr = fPathPts.begin();
+    const SkPoint* finalCurveStart = NULL;
+    const SkPoint* finalCurveEnd = NULL;
+    SkPath::Verb verb;
+    while ((verb = (SkPath::Verb) *verbPtr++) != SkPath::kDone_Verb) {
+        switch (verb) {
+            case SkPath::kMove_Verb:
+                complete();
+                if (!fCurrentContour) {
+                    fCurrentContour = fContours.push_back_n(1);
+                    fCurrentContour->setOperand(fOperand);
+                    fCurrentContour->setXor(fXorMask[fOperand] == kEvenOdd_PathOpsMask);
+                    *fExtra.append() = -1;  // start new contour
+                }
+                finalCurveEnd = pointsPtr++;
+                goto nextVerb;
+            case SkPath::kLine_Verb:
+                // skip degenerate points
+                if (pointsPtr[-1].fX != pointsPtr[0].fX || pointsPtr[-1].fY != pointsPtr[0].fY) {
+                    fCurrentContour->addLine(&pointsPtr[-1]);
+                }
+                break;
+            case SkPath::kQuad_Verb:
+                reducedVerb = SkReduceOrder::Quad(&pointsPtr[-1], &fReducePts);
+                if (reducedVerb == 0) {
+                    break;  // skip degenerate points
+                }
+                if (reducedVerb == 1) {
+                    *fExtra.append() =
+                            fCurrentContour->addLine(fReducePts.end() - 2);
+                    break;
+                }
+                fCurrentContour->addQuad(&pointsPtr[-1]);
+                break;
+            case SkPath::kCubic_Verb:
+                reducedVerb = SkReduceOrder::Cubic(&pointsPtr[-1], &fReducePts);
+                if (reducedVerb == 0) {
+                    break;  // skip degenerate points
+                }
+                if (reducedVerb == 1) {
+                    *fExtra.append() = fCurrentContour->addLine(fReducePts.end() - 2);
+                    break;
+                }
+                if (reducedVerb == 2) {
+                    *fExtra.append() = fCurrentContour->addQuad(fReducePts.end() - 3);
+                    break;
+                }
+                fCurrentContour->addCubic(&pointsPtr[-1]);
+                break;
+            case SkPath::kClose_Verb:
+                SkASSERT(fCurrentContour);
+                if (finalCurveStart && finalCurveEnd
+                        && *finalCurveStart != *finalCurveEnd) {
+                    *fReducePts.append() = *finalCurveStart;
+                    *fReducePts.append() = *finalCurveEnd;
+                    *fExtra.append() = fCurrentContour->addLine(fReducePts.end() - 2);
+                }
+                complete();
+                goto nextVerb;
+            default:
+                SkDEBUGFAIL("bad verb");
+                return;
+        }
+        finalCurveStart = &pointsPtr[verb - 1];
+        pointsPtr += verb;
+        SkASSERT(fCurrentContour);
+    nextVerb:
+        if (verbPtr == endOfFirstHalf) {
+            fOperand = true;
+        }
+    }
+}