new files for pathops geometric intersection

src/pathops/SkOpBuilder.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "SkMatrix.h"
+#include "SkPath.h"
+#include "SkPathOps.h"
+
+void SkOpBuilder::add(const SkPath& path, SkPathOp op) {
+    if (0 == fOps.count() && op != kUnion_PathOp) {
+        fPathRefs.push_back() = SkPath();
+        *fOps.append() = kUnion_PathOp;
+    }
+    fPathRefs.push_back() = path;
+    *fOps.append() = op;
+}
+
+void SkOpBuilder::reset() {
+    fPathRefs.reset();
+    fOps.reset();
+}
+
+/* OPTIMIZATION: Union doesn't need to be all-or-nothing. A run of three or more convex
+   paths with union ops could be locally resolved and still improve over doing the
+   ops one at a time. */
+bool SkOpBuilder::resolve(SkPath* result) {
+    int count = fOps.count();
+    bool allUnion = true;
+    SkPath::Direction firstDir;
+    for (int index = 0; index < count; ++index) {
+        SkPath* test = &fPathRefs[index];
+        if (kUnion_PathOp != fOps[index] || test->isInverseFillType()) {
+            allUnion = false;
+            break;
+        }
+        // If all paths are convex, track direction, reversing as needed.
+        if (test->isConvex()) {
+            SkPath::Direction dir;
+            if (!test->cheapComputeDirection(&dir)) {
+                allUnion = false;
+                break;
+            }
+            if (index == 0) {
+                firstDir = dir;
+            } else if (firstDir != dir) {
+                SkPath temp;
+                temp.reverseAddPath(*test);
+                *test = temp;
+            }
+            continue;
+        }
+        // If the path is not convex but its bounds do not intersect the others, simplify is enough.
+        const SkRect& testBounds = test->getBounds();
+        for (int inner = 0; inner < index; ++inner) {
+            // OPTIMIZE: check to see if the contour bounds do not intersect other contour bounds?
+            if (SkRect::Intersects(fPathRefs[inner].getBounds(), testBounds)) {
+                allUnion = false;
+                break;
+            }
+        }
+    }
+    if (!allUnion) {
+        *result = fPathRefs[0];
+        for (int index = 1; index < count; ++index) {
+            if (!Op(*result, fPathRefs[index], fOps[index], result)) {
+                reset();
+                return false;
+            }
+        }
+        reset();
+        return true;
+    }
+    SkPath sum;
+    for (int index = 0; index < count; ++index) {
+        if (!Simplify(fPathRefs[index], &fPathRefs[index])) {
+            reset();
+            return false;
+        }
+        sum.addPath(fPathRefs[index]);
+    }
+    reset();
+    return Simplify(sum, result);
+}