reenable direction test, fix handling of degenerate segments in the non-convex case
git-svn-id: http://skia.googlecode.com/svn/trunk@3021 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkPath.cpp b/src/core/SkPath.cpp
index fc2ba42..c99db4c 100644
--- a/src/core/SkPath.cpp
+++ b/src/core/SkPath.cpp
@@ -1926,6 +1926,20 @@
return maxIndex;
}
+static int find_diff_pt(const SkPoint pts[], int index, int n, int inc) {
+ int i = index;
+ for (;;) {
+ i = (i + inc) % n;
+ if (i == index) { // we wrapped around, so abort
+ break;
+ }
+ if (pts[index] != pts[i]) { // found a different point, success!
+ break;
+ }
+ }
+ return i;
+}
+
bool SkPath::cheapComputeDirection(Direction* dir) const {
// don't want to pay the cost for computing this if it
// is unknown, so we don't call isConvex()
@@ -1935,10 +1949,15 @@
for (; !iter.done(); iter.next()) {
int n = iter.count();
- const SkPoint* pts = iter.pts();
+ if (n < 3) {
+ continue;
+ }
+ const SkPoint* pts = iter.pts();
SkScalar cross = 0;
if (kConvex_Convexity == conv) {
+ // we loop, skipping over degenerate or flat segments that will
+ // return 0 for the cross-product
for (int i = 0; i < n - 2; ++i) {
cross = cross_prod(pts[i], pts[i + 1], pts[i + 2]);
if (cross) {
@@ -1946,10 +1965,24 @@
}
}
} else {
- int i = find_max_y(pts, n);
- // can't always say (i-1) % n, in case i-1 goes negative, so we
- // use (i+n-1) % n instead
- cross = cross_prod(pts[(i + n - 1) % n], pts[i], pts[(i + 1) % n]);
+ int index = find_max_y(pts, n);
+ // Find a next and prev index to use for the cross-product test,
+ // but we try to find pts that form non-zero vectors from pts[index]
+ //
+ // Its possible that we can't find two non-degenerate vectors, so
+ // we have to guard our search (e.g. all the pts could be in the
+ // same place).
+
+ // we pass n - 1 instead of -1 so we don't foul up % operator by
+ // passing it a negative LH argument.
+ int prev = find_diff_pt(pts, index, n, n - 1);
+ if (prev == index) {
+ // completely degenerate, skip to next contour
+ continue;
+ }
+ int next = find_diff_pt(pts, index, n, 1);
+ SkASSERT(next != index);
+ cross = cross_prod(pts[prev], pts[index], pts[next]);
}
if (cross) {
if (dir) {