If boolean has a true boolean value such as 1 or on then propagation is enabled for master, which must be a window name (see "GEOMETRY PROPAGATION" below). If boolean has a false boolean value then propagation is disabled for master. In either of these cases an empty string is returned. If boolean is omitted then the command returns 0 or 1 to indicate whether propagation is currently enabled for master. Propagation is enabled by default.
The packer normally computes how large a master must be to just exactly meet the needs of its slaves, and it sets the requested width and height of the master to these dimensions. This causes geometry information to propagate up through a window hierarchy to a top-level window so that the entire sub-tree sizes itself to fit the needs of the leaf windows. However, the pack propagate command may be used to turn off propagation for one or more masters. If propagation is disabled then the packer will not set the requested width and height of the packer. This may be useful if, for example, you wish for a master window to have a fixed size that you specify.
Pack propagation to the toplevel window is a special case in one respect. If you have used a wm geometry command such as wm geometry . 400x300, then propagation will seem turned off even though pack propagate . returns 1. To get propagation working again, if needed, issue a wm geometry . "". This effect is described glancingly in the wm man page. RT 19Feb2005