The visual differences between the GNOME and KDE desktop environments are easy to see, so how is it possible to run an app from one under the other without problems? Today’s SuperUser Q&A post has the answer.

Today’s Question & Answer session comes to us courtesy of SuperUser—a subdivision of Stack Exchange, a community-driven grouping of Q&A web sites.

‘Shaking Hands’ clipart courtesy of

The Question

SuperUser reader LeNoob wants to know how KDE apps are able to run under GNOME:

If GNOME uses GTK+ and KDE uses Qt, how are KDE applications able to run under GNOME?

What makes it possible for KDE apps to run smoothly under GNOME?

The Answer

SuperUser contributor grawity has the answer for us:

This is possible because these desktop environments use the same graphics system, X11. All graphical programs only talk the X11 protocol with an X server (usually Xorg), sending commands to draw this or that, and receiving input events (mouse, keyboard, etc.).

Each UI toolkit like GTK or Qt comes in the form of libraries that the graphical program links against. A program written for GNOME will use libgdk and libgtk, and a KDE program will use libQtCore with libQtGui. Both toolkits then simply use the same X11 functions to draw everything in the respective program’s window.

Most modern toolkits, like GTK, Qt, or EFL, perform all drawing themselves, and just send the finished image of the whole window over X11. Older toolkits like Xaw or Motif instead send commands to draw primitives like lines or rectangles, and the X server does all rendering.

The X11 protocol also covers window management, so each desktop environment will have a “window manager” program which draws window frames (“decorations”), allows you to move and resize windows, and so on. Modern “compositing” window managers actually take over Xorg’s job of composing all windows onto the final screen image, allowing things like shadows or effects to be added.

Tying into the same graphics system for easy “compatibility” is an awesome thing, and great when you want to have all your favorite apps running under the same desktop environment!

Have something to add to the explanation? Sound off in the comments. Want to read more answers from other tech-savvy Stack Exchange users? Check out the full discussion thread here.

Akemi Iwaya
Akemi Iwaya has been part of the How-To Geek/LifeSavvy Media team since 2009. She has previously written under the pen name "Asian Angel" and was a Lifehacker intern before joining How-To Geek/LifeSavvy Media. She has been quoted as an authoritative source by ZDNet Worldwide.
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