Tk::pack - Geometry manager that packs around edges of cavity |
Tk::pack - Geometry manager that packs around edges of cavity
$widget->pack?(args)?
$widget->packOption?(args)?
The pack method is used to communicate with the packer, a geometry manager that arranges the children of a parent by packing them in order around the edges of the parent.
In this perl port of Tk it is normal to pack widgets one-at-a-time using the widget object to be packed to invoke a method call. This is a slight distortion of underlying Tk interface (which can handle lists of windows to one pack method call) but has proven effective in practice.
The pack method can have any of several forms, depending on Option:
slave(s)
at the end of the packing order for the master
window given by $master.
slave(s)
will be packed against.
Must be left, right, top, or bottom.
Defaults to top.
If no -in, -after or -before option is specified then slave will be inserted at the end of the packing list for its parent unless it is already managed by the packer (in which case it will be left where it is). If one of these options is specified then slave will be inserted at the specified point. If the slave are already managed by the geometry manager then any unspecified options for them retain their previous values rather than receiving default values.
For each master the packer maintains an ordered list of slaves called the packing list. The -in, -after, and -before configuration options are used to specify the master for each slave and the slave's position in the packing list. If none of these options is given for a slave then the slave is added to the end of the packing list for its parent.
The packer arranges the slaves for a master by scanning the packing list in order. At the time it processes each slave, a rectangular area within the master is still unallocated. This area is called the cavity; for the first slave it is the entire area of the master.
For each slave the packer carries out the following steps:
Once a given slave has been packed, the area of its parcel is subtracted from the cavity, leaving a smaller rectangular cavity for the next slave. If a slave doesn't use all of its parcel, the unused space in the parcel will not be used by subsequent slaves. If the cavity should become too small to meet the needs of a slave then the slave will be given whatever space is left in the cavity. If the cavity shrinks to zero size, then all remaining slaves on the packing list will be unmapped from the screen until the master window becomes large enough to hold them again.
If a master window is so large that there will be extra space left over after all of its slaves have been packed, then the extra space is distributed uniformly among all of the slaves for which the -expand option is set. Extra horizontal space is distributed among the expandable slaves whose -side is left or right, and extra vertical space is distributed among the expandable slaves whose -side is top or bottom.
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 packPropagate method 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.
The master for each slave must either be the slave's parent (the default) or a descendant of the slave's parent. This restriction is necessary to guarantee that the slave can be placed over any part of its master that is visible without danger of the slave being clipped by its parent.
If the master for a slave is not its parent then you must make sure that the slave is higher in the stacking order than the master. Otherwise the master will obscure the slave and it will appear as if the slave hasn't been packed correctly. The easiest way to make sure the slave is higher than the master is to create the master window first: the most recently created window will be highest in the stacking order. Or, you can use the raise and lower methods to change the stacking order of either the master or the slave.
geometry manager, location, packer, parcel, propagation, size
Tk::pack - Geometry manager that packs around edges of cavity |