Emacs isn’t displayed correctly in kde4 when maximized. I found a solution here:
I just found the solution to something that’s been bothering me for a LONG time and want to share it with you:
How to display emacs as a maximized window on KDE4 without emacs resizing itself. I guess most people who use emacs in KDE now about the problem: Once you try to maximize the window, emacs resizes itself to a slightly smaller portion of the screen. This is because emacs rejects the geometry given to it by KWin, because it’s not an integral multiple of the width/height of one character. This might be related my font selection but I don’t think so.
The workaround I found works as follows: Right-click the emacs title bar, select “Advanced”, select “Special Window Settings”. Go to the “Workarounds” tab. Select the checkbox “Strictly obey geometry” and select “Force” from the pulldown menu next to it. Make sure the last checkbox on the right is UNCHECKED!
That should do it. Hope I was able to help people with this.