AIX Version 4.3 Differences Guide

8.3.1.3 Combo Box
As its name indicates, Combo Box combines the capabilities of a single line text
widget and a list widget that allows users to type in information and also provides
a list of choices to complete the text entry field. The list can either be displayed at
all times or dropped down by the user. That is why Combo Box is sometimes
referred to as drop-down list. An example of a Combo Box is shown on the top right
of Figure 47 with the label Leinad.rev.
When the list portion of the Combo Box is hidden, users are given a visual cue, a
downward-pointing arrow next to the text field. These drop down Combo Boxes
are useful when presentation space is limited or when users will complete the text
entry field more often by typing text than by choosing the entry field text from the
list. The drop down Combo Box list should pop-up in the visible area of the screen
but stay aligned with the text field (that is, at the bottom-edge of the screen, the
list will be up).
The application programmer provides an array of strings that will fill the list. Each
string becomes an item in the list, with the first string becoming the item in
position one, the second string becoming the item in position two, and so on. The
list can actually be manipulated with the regular API of the XmList widget.
Similarly, the text entry may be accessed by using XmTextField API. The size of
the list is set by specifying the number of items that are visible in the list
(XmNvisibleItemCount). If the number of items in the list exceeds the number of
items that are visible, a vertical scroll bar will appear that allows the user to scroll
easily through a large number of items.
A Combo Box allows a single item to be selected in two ways: by scrolling
through the List and selecting the desired item, or by entering text into the text
entry field. Selecting an item from the list causes that item to be displayed in the
text portion of the Combo Box. The single-line text field in a Combo Box can be
either editable or non-editable. If the text field is editable, the user can type
directly into it to enter a new list item. If the application needs to validate the
entered text, it can do so by installing a XmNmodifyVerifyCallbacks on the text
field. If the text field is non-editable, typing text invokes a matching algorithm that
attempts to match the entered text with items in the list.
8.3.1.4 Spin Box
Although more modest, the Spin Box widget offers a quick way of selecting,
cycling, or setting a value within a range. It can be used by a very large range of
applications. The Spin Box function can be implemented using the existing Motif
Arrow Button widget and a label widget. However, the Spin Box widget makes it
much easier for the developer and uses much less memory.
8.3.2 Motif Changes in Behavior
The following changes have been made to the behavior of Motif 2.1:
• Take focus without activating on Ctrl+Btn1 in List and Button widgets.
• Supports an indeterminate state and associated visual in the existing toggle
button and toggle button gadget. The indeterminate state is useful in
application property sheets.
Graphical Environment Enhancements 217