I ran into a problem when putting together a Dakboard powered by a Raspberry Pi 4. When I changed the display orientation to portrait only half of the screen was being used.
My Raspberry Pi is running Raspbian Release 10 Codename Buster. The problem was visible on two different monitors so I knew the problem was with the Raspberry Pi.
I had changed the orientation by editing /boot/config.txt to include the following:
# Display orientation. Landscape = 0, Portrait = 1 display_rotate=1
As this didn’t work as expected I set display_rotate=0 and rebooted the Pi and looked for a different way for changing the screen orientation.
Fortunately Raspbian comes with a screen configuration tool that is accessible from the Raspbian preferences menu:
Once the Screen configuration tool is running; select configure, then screens, then HDMI and finally Orientation. You will then have a number of options. After making the appropriate selection and rebooting, the display is now full screen.