Bdtyktl

My friend running Ubuntu just called me saying: "my screen got flipped, how to fix it?"

I told him how to fix it but that raises the question, why is it possible to flip the screen? On Linux you could flip the screen, on windows you could make it rotate sideways.

I can't think of any reason that would make the feature useful, if you want to rotate a picture you could do that in the image viewer.

What type of users flip their Linux or Windows screens? For whom is this feature created?

One common case where you'd want to turn your screen upside down is if you have a laptop doubling as a tablet computer, like this:

Another common case is if you attach a projector to the roof instead of letting it stand on a table.

One can envision a circumstance in which the display mounting and associated brackets can only permit an inverted attachment of the panel. A kiosk with limited access may be one example, a display unit mounted at ceiling height with a mounting bracket that cannot be attached unless upside down.

In the case of a laptop, I can picture a situation in which the keyboard is mounted inside a box with the display extending outside the enclosure which would require to invert the image for viewing in a normal orientation.

I expect there are other circumstances in which this applies.

Addressing the sideways rotation part of the question, the main time I've done so is when I've wanted to see many lines of content at once, e.g. a long file of code, a terminal output, or a spreadsheet. Some desktop monitors (e.g. this one) have a stand that rotates by 90°, but the software needs to rotate the video output too, otherwise everything becomes harder to read.

Many restaurants show their menus on rotated screen (portrait mode); same for airports Departure and Arrival lists. Newer ones are simple oversize screens with 90 degree rotated display.

Others have already mentioned reasons for mirroring (projecting via a mirror to fold the distance needed; or back-projecting), and for 180 degree rotations (set-up tablets, etc.)

I know probably not many do this, but for some time that I had my desktop monitor close to where my head's at in bed, I would rotate the screen so I could read or watch a movie while laying on my side. I've also done that with my laptop a few times.