How to draw a line in the Desktop Context or Device Context in SwiftUI on macOS

Question

I am a newbie in SwiftUI and macOS. The title say is all, I gonna draw a line in the macOS desktop. It means I draw 1 line on the top layer of the desktop and I can interact with the desktop as usual. I have finished the same with GetWindowDC in winApi and GDI in C++.

The GetWindowDC function retrieves the device context (DC) for the entire window, including title bar, menus, and scroll bars.

How can I found the way to do it instead..

I have found

NSGraphicsContext.current!.cgContext

as the quite similar with WinApi but it still not worked for macOS

Answer 1

Update: I have found a workaround solution:

1. I create a Floating Panel with the transparent backgrounds which is the inherited from NSPanel class.
2. Then I add the setting:

      // Allow the pannel to be on top of almost all other windows
      self.isFloatingPanel = true
      self.level = .floating
    
      // Allow the pannel to appear in a fullscreen space
      self.collectionBehavior.insert(.fullScreenAuxiliary)
    
      // While we may set a title for the window, don't show it
      self.titleVisibility = .hidden
      self.titlebarAppearsTransparent = true
    
      // Since there is no titlebar make the window moveable by click-dragging on the background
      self.isMovableByWindowBackground = false
      // Allow user can interact with the desktop components under your panel.
      self.ignoresMouseEvents = true

3. Draw something in this floating panel.

Hope this information is useful.