There are supposed to be borders left and right if you have a widescreen screen monitor.

We really could use a newer official version of DOSBox.

Then seeing borders at the sides is normal. Those games were made for 4:3 monitors. Otherwise, the image will be stretched,

When Arena is in fullscreen:
- the monitor OSD says my resolution is 800x600.
- fullscreen= (it equals nothing)
- I use Direct3D or OpenGL (that does not matter)
- I use hq2x or any other 2x scaler (so not hq3x or any other 3x scaler)

You should put your monitor resolution as fullscreen : 1920x1080
Just don't use the hqXx filters. If the opengl filtering is not enough, use advmame3x or advinterp3x, that should be good, and without top and bottom black borders.

Also, it's not related, but if your monitor is 1920x1080, why is your windowed resolution 1920x1200 ? Maybe put something smaller, like 1365x768.

Thanks for help to you all.
I will probably rather play with hq2x since I am clueless with hq3x.

Exactly, the borders are there because the only other options are to cut the top and bottom off or make everyone fat.

try:

output=openglnb
fullresolution=0x0
aspect=true
scaler=none


Note that if there are multiple .conf files, it's possible for one of them to override another's settings.... Had that happen with EWJ games.

So why there are no borders with 2x scalers or with any scalers? But with 3x scalers yes.

So, just to make sure I understand correctly: When you have it set to 2x scalers you get a completely full screen image that fills your wide screen monitor?

Yes, with 2x scaler, or no scaler, I have fullscreen.

It shouldn't be. The situation you're asking us to recreate is wrong and probably caused by a bug or wrong setting in your video card control panel (or monitor). This behaviour here is correct, you're asking for help to break that. I give up. :P

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All those scalers seem to be bugged, some more than others. On my computer, setting the hq3x slightly diminishes the game's window, while setting the hq2x nearly halves it. This should not happen and is related to the scaler filters.
When going fullscreen, because of these bugged scaler filters, the image is not streched so this results in those small or big black borders on the top and the bottom.

If you don't have a border with a 2x one, then you are just "lucky" : when I use the hq2x for example, with no fullresolution set, i get black borders too, and my monitor sets itself in 640x480.



This screen doesn't include the black borders on the left / right.