improve clamping logic when handling imprecise chopping of cubics
http://code.google.com/p/skia/issues/detail?id=444
git-svn-id: http://skia.googlecode.com/svn/trunk@3011 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkEdgeClipper.cpp b/src/core/SkEdgeClipper.cpp
index d8cb75b..d77f6f8 100644
--- a/src/core/SkEdgeClipper.cpp
+++ b/src/core/SkEdgeClipper.cpp
@@ -266,20 +266,21 @@
// Modify pts[] in place so that it is clipped in Y to the clip rect
static void chop_cubic_in_Y(SkPoint pts[4], const SkRect& clip) {
- SkScalar t;
- SkPoint tmp[7]; // for SkChopCubicAt
// are we partially above
if (pts[0].fY < clip.fTop) {
+ SkScalar t;
if (chopMonoCubicAtY(pts, clip.fTop, &t)) {
+ SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
- // given the imprecision of computing t, we just slam our Y coord
- // to the top of the clip. This also saves us in the bad case where
- // the t was soooo bad that the entire segment could have been
- // below fBottom
+
+ // tmp[3, 4, 5].fY should all be to the below clip.fTop, and
+ // still be monotonic in Y. Since we can't trust the numerics of
+ // the chopper, we force those conditions now
tmp[3].fY = clip.fTop;
- clamp_ge(tmp[4].fY, clip.fTop);
- clamp_ge(tmp[5].fY, clip.fTop);
+ tmp[4].fY = SkMaxScalar(tmp[4].fY, clip.fTop);
+ tmp[5].fY = SkMaxScalar(tmp[5].fY, tmp[4].fY);
+
pts[0] = tmp[3];
pts[1] = tmp[4];
pts[2] = tmp[5];
@@ -294,7 +295,9 @@
// are we partially below
if (pts[3].fY > clip.fBottom) {
+ SkScalar t;
if (chopMonoCubicAtY(pts, clip.fBottom, &t)) {
+ SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
clamp_le(tmp[1].fY, clip.fBottom);
clamp_le(tmp[2].fY, clip.fBottom);
@@ -341,18 +344,22 @@
this->appendVLine(clip.fRight, pts[0].fY, pts[3].fY, reverse);
return;
}
-
- SkScalar t;
- SkPoint tmp[7];
-
+
// are we partially to the left
if (pts[0].fX < clip.fLeft) {
+ SkScalar t;
if (chopMonoCubicAtX(pts, clip.fLeft, &t)) {
+ SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
this->appendVLine(clip.fLeft, tmp[0].fY, tmp[3].fY, reverse);
- clamp_ge(tmp[3].fX, clip.fLeft);
- clamp_ge(tmp[4].fX, clip.fLeft);
- clamp_ge(tmp[5].fX, clip.fLeft);
+
+ // tmp[3, 4, 5].fX should all be to the right of clip.fLeft, and
+ // still be monotonic in X. Since we can't trust the numerics of
+ // the chopper, we force those conditions now
+ tmp[3].fX = clip.fLeft;
+ tmp[4].fX = SkMaxScalar(tmp[4].fX, clip.fLeft);
+ tmp[5].fX = SkMaxScalar(tmp[5].fX, tmp[4].fX);
+
pts[0] = tmp[3];
pts[1] = tmp[4];
pts[2] = tmp[5];
@@ -366,7 +373,9 @@
// are we partially to the right
if (pts[3].fX > clip.fRight) {
+ SkScalar t;
if (chopMonoCubicAtX(pts, clip.fRight, &t)) {
+ SkPoint tmp[7];
SkChopCubicAt(pts, tmp, t);
clamp_le(tmp[1].fX, clip.fRight);
clamp_le(tmp[2].fX, clip.fRight);
diff --git a/tests/ClipperTest.cpp b/tests/ClipperTest.cpp
index 0f5a615..f6333ba 100644
--- a/tests/ClipperTest.cpp
+++ b/tests/ClipperTest.cpp
@@ -10,6 +10,24 @@
#include "SkLineClipper.h"
#include "SkEdgeClipper.h"
+static void test_edgeclipper(skiatest::Reporter* reporter) {
+ SkEdgeClipper clipper;
+
+ const SkPoint pts[] = {
+ { 3.0995476e+010, 42.929779 },
+ { -3.0995163e+010, 51.050385 },
+ { -3.0995157e+010, 51.050392 },
+ { -3.0995134e+010, 51.050400 },
+ };
+
+ const SkRect clip = { 0, 0, 300, 200 };
+
+ // this should not assert, even though our choppers do a poor numerical
+ // job when computing their t values.
+ // http://code.google.com/p/skia/issues/detail?id=444
+ clipper.clipCubic(pts, clip);
+}
+
static void test_intersectline(skiatest::Reporter* reporter) {
static const SkScalar L = 0;
static const SkScalar T = 0;
@@ -90,6 +108,7 @@
void TestClipper(skiatest::Reporter* reporter) {
test_intersectline(reporter);
+ test_edgeclipper(reporter);
}
#include "TestClassDef.h"