Add a linear curve constant. (#16)

material-motion · Nov 2, 2017 · 0aa4f8c · 0aa4f8c
1 parent f5a7f3b
commit 0aa4f8c
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diff --git a/src/MDMMotionCurve.h b/src/MDMMotionCurve.h
@@ -141,6 +141,11 @@ typedef NS_ENUM(NSUInteger, MDMSpringMotionCurveDataIndex) {
               friction }                    \
   }
 
+/**
+ A linear bezier motion curve.
+ */
+#define MDMLinearMotionCurve _MDMBezier(0, 0, 1, 1)
+
 /**
  Timing information for an iOS modal presentation slide animation.
  */

diff --git a/tests/unit/MDMMotionCurveTests.m b/tests/unit/MDMMotionCurveTests.m
@@ -23,6 +23,25 @@ @interface MDMMotionCurveTests : XCTestCase
 
 @implementation MDMMotionCurveTests
 
+- (void)testLinearCurveConstantMatchesSystemLinearCurve {
+  MDMMotionCurve curve = MDMLinearMotionCurve;
+  CAMediaTimingFunction *linearTimingFunction =
+      [CAMediaTimingFunction functionWithName:kCAMediaTimingFunctionLinear];
+  MDMMotionCurve systemLinearCurve = MDMMotionCurveFromTimingFunction(linearTimingFunction);
+  XCTAssertEqualWithAccuracy(curve.data[MDMBezierMotionCurveDataIndexP1X],
+                             systemLinearCurve.data[MDMBezierMotionCurveDataIndexP1X],
+                             0.001);
+  XCTAssertEqualWithAccuracy(curve.data[MDMBezierMotionCurveDataIndexP1Y],
+                             systemLinearCurve.data[MDMBezierMotionCurveDataIndexP1Y],
+                             0.001);
+  XCTAssertEqualWithAccuracy(curve.data[MDMBezierMotionCurveDataIndexP2X],
+                             systemLinearCurve.data[MDMBezierMotionCurveDataIndexP2X],
+                             0.001);
+  XCTAssertEqualWithAccuracy(curve.data[MDMBezierMotionCurveDataIndexP2Y],
+                             systemLinearCurve.data[MDMBezierMotionCurveDataIndexP2Y],
+                             0.001);
+}
+
 - (void)testBezierCurveData {
   MDMMotionCurve curve = MDMMotionCurveMakeBezier(0.1f, 0.2f, 0.3f, 0.4f);
   XCTAssertEqualWithAccuracy(curve.data[MDMBezierMotionCurveDataIndexP1X], 0.1, 0.001);