test & doc for SkUnitCubicInterp
R=reed@google.com
BUG=skia:959
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1562333002
Review URL: https://codereview.chromium.org/1562333002
diff --git a/tests/InterpolatorTest.cpp b/tests/InterpolatorTest.cpp
index 3cfd19f..f520ebb 100644
--- a/tests/InterpolatorTest.cpp
+++ b/tests/InterpolatorTest.cpp
@@ -58,4 +58,35 @@
result = inter.timeToValues(175, v);
REPORTER_ASSERT(reporter, result == SkInterpolator::kNormal_Result);
+ for (SkScalar val = -0.1f; val <= 1.1f; val += 0.1f) {
+ REPORTER_ASSERT(reporter, SkScalarNearlyEqual(SkTPin(0.f, val, 1.f),
+ SkUnitCubicInterp(val, 1.f/3, 1.f/3, 2.f/3, 2.f/3)));
+ }
+
+ // These numbers come from
+ // http://www.w3.org/TR/css3-transitions/#transition-timing-function_tag.
+ const SkScalar testTransitions[][4] = {
+ { 0.25f, 0.1f, 0.25f, 1 }, // ease
+ { 0.42f, 0, 1, 1 }, // ease in
+ { 0, 0, 0.58f, 1 }, // ease out
+ { 0.42f, 0, 0.58f, 1 }, // ease in out
+ };
+
+ const SkScalar expectedOutput[][5] = {
+ { 0.0947876f, 0.513367f, 0.80249f, 0.940796f, 0.994263f }, // ease
+ { 0.0170288f, 0.129639f, 0.31543f, 0.554749f, 0.839417f }, // ease in
+ { 0.160583f, 0.445251f, 0.684692f, 0.870361f, 0.982971f }, // ease out
+ { 0.0197144f, 0.187439f, 0.500122f, 0.812561f, 0.980286f }, // ease in out
+ };
+
+ int i = 0;
+ for (const SkScalar* t : testTransitions) {
+ int j = 0;
+ for (SkScalar val = 0.1f; val < 1; val += 0.2f) {
+ REPORTER_ASSERT(reporter, SkScalarNearlyEqual(expectedOutput[i][j++],
+ SkUnitCubicInterp(val, t[0], t[1], t[2], t[3])));
+ }
+ ++i;
+ SkDebugf("\n");
+ }
}