[PATCH 0/1] MR9176: winemac: Draw black letter/pillarboxes around full-screen content.

[Brendan Shanks (＠bshanks)]

Currently on macOS when display mode emulation is enabled, the space (letterboxes/pillarboxes) around the scaled full-screen content is usually white. We want it to be black instead, like it would be in the case of a real display mode change.

To do this: in `WindowPosChanged` when `fullscreen == TRUE`, cover the window with black borders so that only the `window` rect is visible. A `CAShapeLayer` is used, and added as a sublayer to the window's `contentView.layer`.