This function returns a drawable ID used to refer to the back buffer of the
specified window. The swap_action is a hint to indicate the swap
action that will likely be used in subsequent calls to
XdbeSwapBuffers(X3xext).
The actual swap
action used in calls to
XdbeSwapBuffers
does not have to be the same as the
swap_action passed to this function, though clients are encouraged
to provide accurate information whenever possible.
Diagnostics
BadAlloc, BadIDChoice , BadMatch
The specified window is not an InputOutput window or its visual does not
support DBE.