<p>I'm looking for patterns that concern coding parts of a GUI. <strong>Not</strong> as global as <strong>MVC</strong>, that I'm quite familiar with, but patterns and good ideas and best practices concerning single controls and inputs.</p>

<p>Let say I want to make a control that display some objects that may overlap. Now if I click on an object, I need to find out what to do (Just finding the object I can do in several ways, such as an quad-tree and Z-order, thats not the problem). And also I might hold down a modifier key, or some object is active from the beginning, making the selection or whatever a bit more complicated. Should I have an object instance representing a screen object, handle the user-action when clicked, or a master class. etc.. What kind of patterns or solutions are there for problems like this? </p>

I think to be honest you a better just boning up on your standard design patterns and applying them to the individual problems that you face in developing your UI.
While there are common UI "themes" (such as dealing with modifier keys) the actual implementation may vary widely.
I have O'Reilly's
Head First Design Patterns
and
The Poster
, which I have found invaluable!
Shameless Plug : These links are using my associates ID.