OM_UPDATE

This method tells an object to update one or more of its attribute values.

Declaration

Source position: intuition.pas line 2003

Description

This method tells an object to update one or more of its attributes. No application should call this method. Only Boopsi objects send OM_UPDATE messages. The return value for this method is not explicitly defined.

A Boopsi object uses an OM_UPDATE message to notify another Boopsi object about transitory changes to one or more attributes.

From the point of view of most objects, an OM_UPDATE message is almost identical to OM_SET. Because the methods are so similar, When a typical dispatcher receives an OM_UPDATE message, it processes the OM_UPDATE the same way it would process an OM_SET message, usually using the same code.

There are actually two kinds of OM_UPDATE, an interim and final one. While a Boopsi object's attribute is in a transient state, it can send out interim OM_UPDATE messages to its target(s). For example, while the user is sliding a Boopsi prop gadget, the prop gadget sends interim OM_UPDATE message about changes to its PGA_Top value (the integer value of the prop gadget is the PGA_Top attribute) to some target object. When the user lets go of the prop gadget, the gadget is no longer in a transient state, so the gadget sends out a final OM_UPDATE about its PGA_Top attribute. The target object can choose to change one of its attributes based on the OM_UPDATE messages it receives.

The layout of the OM_UPDATE message is almost identical to the OM_SET message

Some dispatchers need to know the difference between an interim and final OM_UPDATE. A dispatcher can tell the difference between an interim and final OM_UPDATE message because the OM_UPDATE message has an extra field for flags. If the low order bit (the OPUF_INTERIM bit) is set, this is an interim OM_UPDATE message. The interim flag is useful to a class that wants to ignore any interim messages, processing only final attribute values.

See also