Tried to take a screenshot of a window in Ubuntu? That is by pressing the keyboard shortcut Alt+Print Screen. You will notice that the window screenshot is missing the window decoration and border! This seems to be a notoriously long standing bug in Ubuntu, 4 years old now! And no solution seems in sight.
Gimp says it can take a screenshot including the window decoration (File → Create → Screenshot). But, I found that the screenshot window decoration missing all the colors and styles of the theme!
A solution that finally worked was the Shutter screenshot tool. I did not like the ginormous list of dependencies it had, but had no other option. To take a window screenshot, choose File → New → Window. I could finally see the window decoration in the screenshot it takes.