Implement Canvas::Skew.

Author: chinmaygarde

impeller/aiks/aiks_unittests.cc

@@ -141,5 +141,17 @@ TEST_F(AiksTest, CanPerformFullScreenMSAA) {
   ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
 }
 
+TEST_F(AiksTest, CanPerformSkew) {
+  Canvas canvas;
+
+  Paint red;
+  red.color = Color::Red();
+
+  canvas.Skew(10, 125);
+  canvas.DrawRect(Rect::MakeXYWH(0, 0, 100, 100), red);
+
+  ASSERT_TRUE(OpenPlaygroundHere(canvas.EndRecordingAsPicture()));
+}
+
 }  // namespace testing
 }  // namespace impeller

impeller/aiks/canvas.cc

@@ -65,6 +65,10 @@ void Canvas::Scale(const Vector3& scale) {
   Concat(Matrix::MakeScale(scale));
 }
 
+void Canvas::Skew(Scalar sx, Scalar sy) {
+  Concat(Matrix::MakeSkew(sx, sy));
+}
+
 void Canvas::Rotate(Radians radians) {
   Concat(Matrix::MakeRotationZ(radians));
 }

impeller/aiks/canvas.h

@@ -47,6 +47,8 @@ class Canvas {
 
   void Scale(const Vector3& scale);
 
+  void Skew(Scalar sx, Scalar sy);
+
   void Rotate(Radians radians);
 
   void DrawPath(Path path, Paint paint);

impeller/geometry/matrix.h

@@ -80,6 +80,15 @@ struct Matrix {
     // clang-format on
   }
 
+  static constexpr Matrix MakeSkew(Scalar sx, Scalar sy) {
+    // clang-format off
+    return Matrix(1.0, sy , 0.0, 0.0,
+                  sx , 1.0, 0.0, 0.0,
+                  0.0, 0.0, 1.0, 0.0,
+                  0.0, 0.0, 0.0, 1.0);
+    // clang-format on
+  }
+
   static Matrix MakeRotation(Scalar radians, const Vector4& r) {
     const Vector4 v = r.Normalize();
 
@@ -112,8 +121,8 @@ struct Matrix {
   }
 
   static Matrix MakeRotationX(Radians r) {
-    Scalar cosine = cos(r.radians);
-    Scalar sine = sin(r.radians);
+    const Scalar cosine = cos(r.radians);
+    const Scalar sine = sin(r.radians);
     // clang-format off
     return Matrix(
       1.0,  0.0,    0.0,    0.0,
@@ -125,8 +134,8 @@ struct Matrix {
   }
 
   static Matrix MakeRotationY(Radians r) {
-    Scalar cosine = cos(r.radians);
-    Scalar sine = sin(r.radians);
+    const Scalar cosine = cos(r.radians);
+    const Scalar sine = sin(r.radians);
 
     // clang-format off
     return Matrix(
@@ -139,8 +148,8 @@ struct Matrix {
   }
 
   static Matrix MakeRotationZ(Radians r) {
-    Scalar cosine = cos(r.radians);
-    Scalar sine = sin(r.radians);
+    const Scalar cosine = cos(r.radians);
+    const Scalar sine = sin(r.radians);
 
     // clang-format off
     return Matrix (
@@ -196,12 +205,14 @@ struct Matrix {
   }
 
   constexpr Matrix Transpose() const {
+    // clang-format off
     return {
-        m[0], m[4], m[8],  m[12],  //
-        m[1], m[5], m[9],  m[13],  //
-        m[2], m[6], m[10], m[14],  //
-        m[3], m[7], m[11], m[15],  //
+        m[0], m[4], m[8],  m[12],
+        m[1], m[5], m[9],  m[13],
+        m[2], m[6], m[10], m[14],
+        m[3], m[7], m[11], m[15],
     };
+    // clang-format on
   }
 
   Matrix Invert() const;

impeller/geometry/shear.cc

@@ -7,10 +7,6 @@
 
 namespace impeller {
 
-std::string Shear::ToString() const {
-  std::stringstream stream;
-  stream << "{" << xy << ", " << xz << ", " << yz << "}";
-  return stream.str();
-}
+//
 
 }  // namespace impeller

impeller/geometry/shear.h

@@ -27,8 +27,6 @@ struct Shear {
   }
 
   bool operator!=(const Shear& o) const { return !(*this == o); }
-
-  std::string ToString() const;
 };
 
 }  // namespace impeller

impeller/geometry/size.cc

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 #include "size.h"
-#include <sstream>
 
 namespace impeller {