Clipboard behavior on Wayland

This is a continuation of #19. I want to do something to get more control over how the clipboard is handled and make persistance work even without clipboard daemon. My constraints:

clipboard should work with the clipboard button and regardless of the file button
clipboard should hold the copied image after program exit on Wayland
clipboard should work as described with but also without clipboard daemon
clipboard should continue to work on other platforms: X11, Darwin, Windows
if necessary, a user config might be okay...

Background Information I gathered during the last days

X11 and Windows (at least) have a proper concept of Clipboard where some "host process" copies and holds the copied data. That means after the copying process exits, the content is still available
Wayland does not have such concept. The content is expected to live inside the copying application and be available for querying.
There are tools that help to circumvent that situation. These are long-lived daemons that monitor the clipboard and hold the data on behalf of the application. Such tools include wayland-clipboard (wl-copy), cliphist, clipmon and others. They all - to some extent - work the same way
Applications can also mimic that behavior by forking itself off and keeping the fork alive until another process takes over the clipboard. Then they "die".
Another option (currently probably my preferred) might be to launch a custom command such as wl-copy and let this process do the "dirty work" of forking and staying alive. That command might also be configurable for the user..
In any case, we need to make sure that other platforms are not affected by the change

gabm / Satty

Clipboard behavior on Wayland #26