Kamesh rao's Public Library

The X clipboard works rather differently from what naive expectations about it might be. There's actually no real clipboard. If you copy something to clipboard in app A, then the only thing that happens is that app A tells X that it's now the owner of the clipboard. The data is still stored in A. And if you later decide to paste the clipboard content in app B, then B has to ask X about who's the clipboard owner and after it's told, it needs to communicate with A and get the contents from it. The most obvious demonstration of this fact is that if you close A, clipboard contents get lost. Another consequence of this fact is that just copying to clipboard is a cheap operation, pasting in the same app is cheap, but pasting in another app is not. If the contents were stored in X, all operations would be expensive. And finally one more interesting fact about X clipboard is that if the owner changes, only the previous owner will be told. If C takes over the clipboard, A will be told, but B won't. There are also other things about X clipboard, like that there are actually two of them, but that's not important here.