GUI Emacs running maximized on my Linux (centos7+kde) is not using all the available space leaving some space around the borders, specially at the top and the bottom.
Sample of GUI emacs running "maximized" where you can still see the desktop wallpaper (and you should not):
All other apps (kde, gnome, etc) don't have this problem, when you click on maximize button, you cannot see the desktop wallpaper (expected behaviour).
In both cases (emacs and any other app) I use the maximize button provided by the OS. Using
M-x toggle-frame-maximized as suggested has the same (wrong) effect. Using
M-x toggle-frame-fullscreen works better in that emacs uses all the screen, but hides the window frame and the OS panel at the bottom, which is not what I want, I just want it to run maximized.
Appreciate if anyone knows how to make GUI Emacs use all the space available when running maximized.