Rectangle

The tool does not paint the image itself. White permits processing, black preserves the receiving operation’s unaffected state, and gray produces partial influence. The receiving tool determines what that means for the image.

Shape position/size, canvas resolution and movement of a colored layer are separate concerns. A reveal can move only the mask while the title and source plate stay fixed.

For a compound shape chain masks and explicitly choose Paint Mode on the receiver. Inspect the matte in monochrome before compositing: random inversion or Blend changes do not reliably fix reversed subtraction.