Volume 6A: Motif Programming Manual

differences.

Because a gadget does not have its own window, it is entirely dependent on its parent, a manager widget, for its basic

functionality. For example, the manager must handle redrawing the gadget on exposure, highlighting it as a result of

keyboard traversal, and notifying it of event activity. Without a window, a gadget has no control over the colors that it

uses or any other window−based attributes normally associated with a widget. For this reason, gadgets can only be

used in managers that support them. How closely a gadget emulates its widget counterpart is largely dependent on the

capabilities of the manager widget parent.

The Motif Manager class limits the colors that can be used by gadgets. A gadget uses the same background,

foreground, and shadow colors as its manager widget parent. These restrictions are not inherent in the Xt Composite

widget class or in Xt−based gadgets; they are specific to the Motif Manager and Gadget classes. Hypothetically, you

could write a Composite widget that allows its gadget children to specify their own background colors. Such a widget

would have to paint the area of its window occupied by the gadget with the specified color to give the user the

impression that the gadget is indeed a separately−colored widget.

You can use the color restrictions of the Motif managers and gadgets to provide a consistent interface for your

application. For example, by using PushButton gadgets instead of PushButton widgets, you can ensure that all of the

buttons ...