It appears that there is a mismatch between the BBB resolution and what the bbcape43 can do. Using the image from element14, my desktop is much larger than the LCD can display.
When I try to change the resolution using preferences->LXQt settings->monitor settings the resolution is set to 480x272, and I can not change it.
Looking at the bbcape43 features page https://www.element14.com/community/docs/DOC-81966 the resolution is correct. But the desktop is about 50% larger in both the X and Y directions.
How can I make the desktop size match the screen size?
Here is a screen shot of what I'm talking about:
You can see that the bottom and right hand side is off the screen area.
It appears that this is just how it is for small screens. Most of the apps assume a larger screen.
My custom app fills the screen just fine.