RetroPie - on the Pi models - doesn't use the desktop at all and it runs as a dedicated application (EmulationStation) from the console. If you want to use your Pi4 as a desktop enabled computer, perhaps it would be better to use Raspberry Pi OS and install the same emulators that RetroPie uses and run them standalone.
You can start RetroPie from the desktop environment, but it's not a supported configuration and not something we recommend.

@d33j4y excellent worked for me don’t understand what cos I thought overscan was the fix , games don’t run full screen that’s my next fix

@mitu ok thanks I will try running it direct from bootup

@mbrett Do you have a screenshot to show the problem ? Have you tried toggling 'Integer scaling' on/off to see if it makes a difference ?

@djwildheart Please add more info about your system, as requested in https://retropie.org.uk/forum/topic/3/read-this-first.

Have you set any custom video modes for the emulator using the Runcommand launch menu ?

@10vorne I dont have any experience running it on a netbook. Sorry! Maybe someone else more knowledgeable in that area might be able to help.

@mediamogul said in Full screen advmame:

I can only imagine how bad vertical games would look.

I think you would run out of stretch parameter, as the max value is 2.0. Running 1080p at that stretch factor, you would end up with 150px pillarbox borders on the sides.

So, it is important to note for @cyclair that if you are planning to fill the screen with vertical games too, you will only get to stretch those to 84% of the widescreen at display_expand 2.0.

@jabbafeet I don't expect other people's numbers to be useful for other cases, as different TV sets have different requirements. I'd encourage you to follow the steps mentioned in the previous posts and understand what ranges work for you in the end. In one monitor I have I don't need these, in another one I end up needing negative values for some reason.