Volume 6A: Motif Programming Manual

cannot access it. Since locking the clipboard is done on a per−window basis, the object that locks the clipboard should

have an associated window, which means that gadgets may not work. Gadgets happen to work in some cases because

of their window−based widget parents. However, some of the clipboard functions use XtWindow() rather than

XtWindowOfObject() to get the window of an object. These functions do not work for gadgets. When the

clipboard is locked, only requests from objects with the same window ID can access the clipboard. Each time an

object requests a lock on the clipboard, a counter is incremented so that matching unlock requests can be honored.

XmClipboardStartCopy() sets up internal storage for the copy to take place, XmClipboardCopy() sends

the data to the clipboard, and XmClipboardEndCopy() frees the internal supporting structures. When copying

data to the clipboard, including copies by name, all three functions must be used.

The from_clipbd() callback routine uses XmClipboardRetrieveCopy() to re-trieve data from the

clipboard. Only a single call is needed for the retrieval of short items, as in this example. However, a three−step

process similar to that for copying data to the clipboard is required for the incremental retrieval of large amounts of

data. We will cover these functions shortly.

18.1.1 Copying Data

The syntax of the functions that copy data to the clipboard is outlined below. Due to the intricacies involved in

providing data to the clipboard, these functions take ...