diff --git a/src/Avalonia.Base/Matrix.cs b/src/Avalonia.Base/Matrix.cs index a72710ffd4..5f5aab4f47 100644 --- a/src/Avalonia.Base/Matrix.cs +++ b/src/Avalonia.Base/Matrix.cs @@ -214,6 +214,21 @@ namespace Avalonia return new Matrix(cos, sin, -sin, cos, 0, 0); } + /// + /// Creates a rotation matrix using the given rotation in radians around center point. + /// + /// The amount of rotation, in radians. + /// The location of center point. + /// + public static Matrix CreateRotation(double radians, Point center) + { + var cos = Math.Cos(radians); + var sin = Math.Sin(radians); + var x = center.X; + var y = center.Y; + return new Matrix(cos, sin, -sin, cos, x * (1.0 - cos) + y * sin, y * (1.0 - cos) - x * sin); + } + /// /// Creates a skew matrix from the given axis skew angles in radians. /// diff --git a/tests/Avalonia.Base.UnitTests/MatrixTests.cs b/tests/Avalonia.Base.UnitTests/MatrixTests.cs index d111c14258..9fccdf25fc 100644 --- a/tests/Avalonia.Base.UnitTests/MatrixTests.cs +++ b/tests/Avalonia.Base.UnitTests/MatrixTests.cs @@ -61,6 +61,20 @@ public class MatrixTests AssertCoordinatesEqualWithReducedPrecision(expected, actual); } + + [Fact] + public void Transform_Point_Should_Return_Correct_Value_For_Rotate_Matrix_With_Center_Point() + { + var expected = Vector2.Transform( + new Vector2(0, 10), + Matrix3x2.CreateRotation((float)Matrix.ToRadians(30), new Vector2(3, 5))); + + var matrix = Matrix.CreateRotation(Matrix.ToRadians(30), new Point(3, 5)); + var point = new Point(0, 10); + var actual = matrix.Transform(point); + + AssertCoordinatesEqualWithReducedPrecision(expected, actual); + } [Fact] public void Transform_Point_Should_Return_Correct_Value_For_Scaled_Matrix()