SwiftUI MagnificationGesture NOT WORKING PROPERLY on Mac - macos

Question

I have a problem with the MagnificationGesture in SwiftUI on the mac. I am writing a Mac app and I want to scale a view. When I run the program, it works fine for a couple of times and then the onChanged closure does not get executed anymore. I am afraid this is a bug... (or do I completely missunderstand something?). I actually found a very recent question on reddit, where someone has the exact same issue: https://www.reddit.com/r/SwiftUI/comments/sd43rk/im_having_an_issue_with_the_magnificationgesture/
I could reproduce the problem in a very simple view:
struct ContentView: View {
var body: some View {
Text("Hello, world!")
.padding()
.gesture(MagnificationGesture()
.onChanged({ value in
print(value)
}))
}
}
I really hope, there is a solution to this...
Frederik :)

Answer 1

I accidentally found a fix. I'm listening for both drag and magnification. Drag changes the x/y offsets of an image. When magnification stopped responding, dragging the image slightly would make magnification work again. So, at the end of each magnification event, I add a small offset. Seems to work.
Image(nsImage: nsImage)
.resizable()
.frame(width: width, height: height)
.scaleEffect(finalAmount + currentAmount)
.offset(x: offsetX, y:offsetY)
.gesture(
DragGesture()
.onChanged { value in
offsetY = value.translation.height + offsetYBuffer
offsetX = value.translation.width + offsetXBuffer
}
.onEnded { value in
offsetXBuffer = value.translation.width + offsetXBuffer
offsetYBuffer = value.translation.height + offsetYBuffer
}
).gesture(
MagnificationGesture()
.onChanged { value in
currentAmount = value - 1
}
.onEnded { value in
finalAmount += currentAmount
currentAmount = 0
offsetY += 0.1 //this seems to fix it
}
)

Answer 2

this is my slightly adapted code – for me it works fine, also after 30 times (macOS 12.2beta, Xcode 13.2.1)
struct ContentView: View {
#State private var scale: CGFloat = 1
var body: some View {
Text("Hello, world!")
.scaleEffect(scale)
.padding()
.frame(width: 400, height: 400)
.contentShape(Rectangle())
.gesture(MagnificationGesture()
.onChanged({ value in
scale = value
print(value)
}))
}
}