Whenever some other window requests the clipboard's contents (e.g. as a result of a "paste" operation) FOX will send a SEL_CLIPBOARD_REQUEST message to the current clipboard owner. Remember, the clipboard owner is the window that called acquireClipboard(). For our example, the main window is acting as the clipboard owner and so it needs to handle the SEL_CLIPBOARD_REQUEST message:
# Handle clipboard request self.connect(SEL_CLIPBOARD_REQUEST) do setDNDData(FROM_CLIPBOARD, FXWindow.stringType, Fox.fxencodeStringData(@clippedCustomer.to_s)) end
The setDNDData() method takes three arguments. The first argument tells FOX which kind of data transfer we're trying to accomplish; as it turns out, this method can be used for drag-and-drop (FROM_DRAGNDROP) and X11 selection (FROM_SELECTION) data transfer as well. The second argument to setDNDData() is the drag type for the data and the last argument is the data itself, a binary string.
If you're wondering why we need to call the fxencodeStringData() module method to preprocess the string returned by the call to Customer#to_s, that's a reasonable thing to wonder about. In order for FOX to play nice with other clipboard-aware applications, it must be able to store string data on the clipboard in the format expected by those applications. Unfortunately, that expected format is platform-dependent and does not always correspond directly to the format that Ruby uses internally to store its string data. The fxencodeStringData() method (and the corresponding fxdecodeStringData() method) provide you with a platform-independent way of sending (or receiving) string data with the stringType drag type.
If you run the program as it currently stands, you should now be able to select a customer from the list, click the "Copy" button and then paste the selected customer data (as a string) into some other application. For example, if you're trying this tutorial on a Windows machine, try pasting into a copy of Notepad or Microsoft Word. The pasted text should look something like:
#<struct Struct::Customer name="Joe Smith", address="123 Maple, Anytown, NC", zip=12345>