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I am now getting more into customizing my Ubuntu experience and want to understand better what all these different things I keep running into are. What is Gnome3 and Gnome2 in relation to GTK3 or GTK2? Are they related at all? Is Gnome3 another version of Unity? What is Unity? What is compiz?

To make this all VERY basic, the core question is: How is the Ubuntu GUI built? What are the elements from the bottom-up that make up the desktop environment?

Trying to understand this better so I know what I need/want in order to have my desktop the way I would like it. If this question is better suited for a forum of some sort, please let me know and I will understand completely.

Thanks in advance!

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up vote 2 down vote accepted

The GUI on Ubuntu is made up of a large number of pieces, working together. At the base level is Gnome 3 (Not to be confused with Gnome Shell). Gnome 3 uses GTK "widgets" to display all the parts of applications on the screen. On top of Gnome 3, Ubuntu uses Compiz and Unity to give the shell, which consists of the launcher, the menu bar, and the other Ubuntu pieces. Unity is the actual shell, while Compiz is what's known as a compositor - it deals with all of the graphics, transparencies, and animations you see.

So, any Gnome 3 theme will theme your Ubuntu box.

Hope this helps!

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So is the Gnome Shell the same type of thing as Compiz or Unity? Does Gnome3 use only GTK3? Why is it that Gnome3 doesn't work with compiz? – RafLance Mar 23 '12 at 17:38
Gnome Shell is the same type of thing as Unity, yeah. Compiz powers Unity's effects and transitions. Gnome Shell uses Mutter to achieve the same. Gnome 3 works fine with Compiz; Gnome Shell is the part that doesn't. I believe Gnome 3 uses GTK3, yes. – Ethan Mar 23 '12 at 17:54

I'm guessing you're at the same point I was a little while ago so I think I can help you understand this all better.

GTK is the graphical toolkit that kinda holds everything together. If you download a GTK theme that's going to change the most stuff. It'll change the way scroll bars, checkboxes, window backgrounds, etc.

Icon Themes are self-explanatory, they change icons... ALL THE ICONS.

Window Themes or Meta-city themes change the window decorations. The topbar of the windows, the close, minimize, maximize buttons, etc.

Compiz is cool. It gives you effects and added functionality but it can be dangerous to mess around with because it allows you to change settings that shouldn't be changed sometimes.

Best thing to do. Download Ubuntu Tweak and play with it. Run the below command in a terminal to do so.

sudo apt-get install ubuntu-tweak

Keep in mind though that Ubuntu Tweak is for using Unity. If you want to use Gnome Shell there's other tweak tools built for that. A Google search on "Customize Unity" or "Customize Gnome Shell" will tell you pretty much everything you need to know.

Hope that helped!

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So I think I have Gnome Shell and GTK3. Is there a way for me to make the actual windows transparent (similar to the Compiz effects) rather than just the top bar? Also, I already have Ubuntu Tweak but changing the transparency settings doesn't change anything. – RafLance Mar 23 '12 at 18:09
If you're using Gnome Shell than compiz and Ubuntu Tweak won't do anything. If you push your mouse to the top left corner of the screen and get an overview of all the apps you have open you're in Gnome Shell. If you push your mouse to the top left corner of the screen and nothing happens, or you get a menu with a few app choices you're in Unity. It's currently easier to customize Unity in my opinion because you have access to Compiz Effects and other stuff. Gnome Shell is customizable through – theFisher86 Mar 23 '12 at 18:16
Thanks alot for this, I was able to find some opacity-related extensions that work pretty well. It seems that Unity is a bit more eye-candyish but I really like the overall minimalist and smooth feel that Gnome Shell has. Thanks again, and have a great one! – RafLance Mar 23 '12 at 18:23

Gnome 2.x utilized GTK 2.0. Gnome 3 is as obvious by the number a next generation Gnome. Gnome 3 uses GTK 3.0 but still supports applications using GTK 2.0 that have yet to be updated for GTK 3.0. If you examine the configuration files for the themes in Ubuntu 11.10 you see that contain configurations for both GTK 2.0 and 3.0.

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