[SR-3941] AffineTransform.rotate(byRadians:) can be wrong

[swift-ci]

Previous ID	SR-3941
Radar	None
Original Reporter	ten (JIRA User)
Type	Bug
Status	Resolved
Resolution	Done

Environment

macOS

Additional Detail from JIRA

Votes	0
Component/s	Foundation
Labels	Bug
Assignee	@filip-sakel
Priority	Medium

md5: e970db366b17d050e3e21a3f0cbd7b11

Issue Description:

var affine = AffineTransform(scale: 2)
affine.rotate(byRadians: .pi / 4)
print(affine)

Prints: {m11:0.707106781186548, m12:0.707106781186547, m21:-0.707106781186547, m22:0.707106781186548, tX:0.0, tY:0.0}
Expected Result: {m11:1.4142135623731, m12:1.41421356237309, m21:-1.41421356237309, m22:1.4142135623731, tX:0.0, tY:0.0}

I'll tell you what

public mutating func rotate(byRadians angle: CGFloat) {
    prepend(AffineTransform(rotationByRadians: angle))
}

[swift-ci]

Comment by Matt Rajca (JIRA)

swiftlang/swift#9481

[swift-ci]

Comment by Matt Rajca (JIRA)

Merged: swiftlang/swift#9481

[swift-ci]

Comment by Takafumi Akutagawa (JIRA)

let point = NSPoint(x: CGFloat(10), y: CGFloat(10))
let tx: CGFloat = 20
let ty: CGFloat = -30
let radian: CGFloat = .pi / 2

var translateThenRotate = AffineTransform(translationByX: tx, byY: ty)
translateThenRotate.rotate(byRadians: radian)
print(translateThenRotate.transform(point))// output: (20.0, 30.0)

var translateThenRotate2 = NSAffineTransform()
translateThenRotate2.translateX(by: tx, yBy: ty)
translateThenRotate2.rotate(byRadians: radian)
print(translateThenRotate2.transform(point))// output: (10.0, -20.0)

Should be same

Test Code

var translateThenRotate = AffineTransform(translationByX: 20, byY: -30)
translateThenRotate.rotate(byRadians: .pi / 2)
checkPointTransformation(translateThenRotate, point: point, expectedPoint: NSPoint(x: CGFloat(10), y: CGFloat(-20)))

[swift-ci]

Comment by Matt Rajca (JIRA)

Looks fixed in both the core libs (I added a test for this case 00562542e5a7fe6e403dba5dbbfee17a0b51673d) as well as Swift 4.0.1 on macOS.

[filip-sakel]

Foundation's AffineTransform seems to have the same issue.

[filip-sakel]

Resolved here.