CallRootUnderWriteLock:
PUBLIC
PROC [proc:
PROC, viewer: Viewer];
Locks the viewer and its root, provided that the viewer is not destroyed, then calls the procedure provided while holding the locks.
CallRootAndLinksUnderWriteLock:
PUBLIC
PROC [proc:
PROC, viewer: Viewer];
Locks the viewer, its root, and all of the links of the root (for split viewers), provided that the viewer is not destroyed, then calls the procedure provided while holding the locks. If the viewer is excessively split then the whole viewer tree is locked during this call.