Feature Request: “Mirror External Monitor to MacBook” (use external display’s native resolution)

[kasperschnack]

Hi Alin,

First off, thanks for mac-utils—these tools are ridiculously handy!

What I’m after
MirrorMacBookToMonitor mirrors the built-in panel onto the external display, but macOS keeps the MacBook’s resolution, so the external screen ends up scaled or letter-boxed. I’d love a sister utility that does the opposite:

Puts the two screens in Mirror mode using the external monitor’s native resolution as the source.

Scales the MacBook panel instead (that one handles scaling gracefully).

Optionally accepts a display ID/name so users with multiple externals can pick which one becomes the “master.”

Why it matters
For presentations, video playback, or just working on a high-DPI external monitor, preserving the external’s sharpness is key. Today I have to dive into System Settings every time or settle for a fuzzy external image.

Possible approach
A MirrorMonitorToMacBook.swift (and compiled binary) that:

Detects the first external monitor (or a user-supplied ID).

Calls the same mirroring APIs you use now (CGConfigureDisplayMirrorOfDisplay / CGDisplaySetDisplayMode), but designates the external’s mode as primary.

Falls back gracefully if no external monitor is connected.

Happy to help test or contribute code—just point me in the right direction.

Thanks again for the awesome repo!

[alin23]

Not sure I understood this correctly. You basically want the opposite? Like MirrorMonitorToMacbook? The same thing that macOS can does when you press Cmd-BrightnessDown (Cmd-F1)?

Or is it something different and maybe you can try to explain it in other words to help me understand better.