Overview of Item Types

Group Items

Items of type group are special items that group other items. Group items do not have any visual appearance, but rather are used just for creating structure. Groups are implemented very efficiently, and may be hierarchical (i.e., contain other groups). Modifying the position of a group implicitly affects all of the members of the group, recursively. Pad++ also supports "tags" which are implicit way of grouping items - but this only works for events. That is, giving several items the same tag allows them all to respond to the same event handlers. Groups explicitly bring items together. Group members are rendered sequentially in the display list. That is, no other objects can appear inbetween group members - they are always above or below all the group members. Raising or lowering a group object raises or lowers all the group members. Raising or lowering a group member raises or lowers the member within the group.

Groups automatically resize themselves to contain all of their members - thus adding, removing, or repositioning a member implicitly changes the size of the group. See the pad addgroupmember and removegroupmember commands and the -member itemconfigure option below for setting group membership, and the getgroup command for testing group membership.

When an event hits a group, it normally passes through the group object to its members. However, it is possible to configure a group object so that it grabs the events and does not pass them through. See the -divisible flag.

Groups are created with widget commands of the following form:

pathName create group [option value option value ...]
There may be any number of option-value pairs, each of which sets one of the configuration options for the item. These same option-value pairs may be used in itemconfigure widget commands to change the item's configuration. The following options are supported for groups:

[27] -divisible boolean

(available only for grid, group, and HTML item types)
Specifies whether events should go to group members. If -divisible is 1 (true), events never go to the group object, but pass through it to the members. If the event is within the bounding box of the group, but does not hit any members, then it will be ignored by the group. If -divisible is 0 (false), then the event will go the group if it is within the bounding box of the group whether there is a member at the place the event points to or not. Defaults to 1 (true).

[28] -members members

(available only for group and HTML item types)
members is a list of object ids that specify the list of members of this group. Setting the members of a group first removes all existing members, and then inserts the new members. The members are rendered in the order they are specified in members.

July 9, 1996 - 9 JUL 1996

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