Suggestion for per-monitor signal blocking function

[VenusGirl]

When using multiple monitors, I want the function to change the rest of the monitor screen to a black blank screen when I want to focus only on a specific monitor.
For example, if you use monitor 2 when you watch a video, you can't focus on watching the video when the monitor 1 and 3 are turned on and bright.
When you want to watch a video or only monitor 2, only monitors 1, 3, or 3 can block or make the signal look black for a while.

[emoacht]

Thank you for the suggestion.
If my understanding is correct, do you mean a combination of operations that reproduce the OS’s "Disconnect this display"?

[VenusGirl]

To be precise, it's not cutting off the connection by blocking the signal, but it's outputting a black screen like a screen protector.

I'm talking about the same behavior as this program
https://multiscreenblank.nookkin.com/index.ndoc

[emoacht]

What do you mean by "screen" in "outputting a black screen"? It is a window which hides all other windows in the monitor?

[VenusGirl]

"Screen" refers to the display (monitor),

and it refers to covering the monitor with black so that it will not be viewed for a while.

[emoacht]

I still do not quite follow your explanation. Technically speaking, what object is that "screen"?
Could you show a real code example?

[VenusGirl]

I mean, I want to make a monitor in black background that I don't want to see for a while.

https://multiscreenblank.nookkin.com/index.ndoc

I suggested that it would be nice to implement the same function as the above program.

[emoacht]

So, could you direct me to the source code of that app? I guess it uses unique techniques that cannot be easily reproduced.

[emoacht]

I found some descriptions on how that app works.

Multiscreen Blank's "blanking" involves placing a black window over the top of everything else.

Screen Mirroring

Although Multiscreen Blank supports a theoretically infinite number of monitors, the monitor on which the Multiscreen Blank window is running must be large enough to fit all monitor controls.

Multiscreen Blank (Classic)

Judging from them, it seems very likely that that app simply places a transparent window over the entire desktop and changes the opacity of the region corresponding to a targeted monitor, making it look as if it were controlling the output to that monitor. This technique would be useful in some scenarios, but fundamentally it's just a visual trick.

I am not denying that app is doing something sophisticated, but it does not really interest me technically.