DEC Text Processing Utility Program Development

5.2 Programming in DECwindows DECTPU

5.2.4.1 Background on DECwindows Callbacks

A callback is a mechanism used by a DECwindows widget to notify an application that the widget has been modified in some way. DECwindows applications have one or more callback routines that define what the application does in response to the callback.

For more information about the use of callbacks and callback routines in DECwindows programs, see the OpenVMS documentation overview.

5.2.4.2Internally Defined DECTPU Callback Routines and Application-Level Callback Action Routines

DECTPU implements the DECwindows concept of callback routines by providing internally defined routines that deliver the information obtained from a widget’s callback to a layered application. These routines are referred to as ‘‘internally defined DECTPU callback routines.’’

When a widget calls back to DECTPU, DECTPU packages the callback information, adds the information to its input queue, and returns to the widget. DECTPU may not process the callback packet on its input queue until later. As a result, the information about the widget that DECTPU gets from the callback may not match the information returned by the GET_INFO (widget_variable, "widget_info") built-in procedure.

When DECTPU processes the callback packet, it uses the CREATE_WIDGET built-in or the SET (WIDGET_CALLBACK) built-in to execute the program or learn sequence that was associated with the widget. This program or learn sequence controls what the application does in response to the callback information passed by the DECTPU callback routines. An application’s callback routines are referred to as ‘‘application-level callback action routines.’’

The following sections present information on internally defined DECTPU callback routines and on application-level callback action routines.

5.2.4.3 Internally Defined DECTPU Callback Routines with UIL

DECTPU declares two internally defined callback routines to the X Resource Manager to handle incoming callbacks and dispatch them to the layered application:

•TPU$WIDGET_INTEGER_CALLBACK—Use this routine as the callback routine for all callbacks that have an integer closure.

•TPU$WIDGET_STRING_CALLBACK—Use this routine as the callback routine for all callbacks that have a string closure.

Although DECwindows lets you specify a different callback routine for each reason that a widget can call back, DECwindows DECTPU does not support this capability. Instead, it provides only the two callback routines mentioned.

Use these callback routines only if you are specifying a widget’s callback resources in a User Interface Language (UIL) file. When a widget is part of an X Resource Manager hierarchy, do not include callback resource names or values in the array you pass to SET (WIDGET). Instead, specify one of the two internally defined callback routines in the UIL file.

5–8DEC Text Processing Utility Program Development

Page 107 Page 109
Page 108
Image 108
Compaq AA-PWCBD-TE manual Background on DECwindows Callbacks, Internally Defined Dectpu Callback Routines with UIL
Page 107 Page 109

AA-PWCBD-TE specifications

The Compaq AA-PWCBD-TE is a highly regarded laptop battery designed to provide reliable power to a range of Compaq laptop models. As technology continues to evolve, the necessity for efficient and long-lasting batteries becomes increasingly important, especially for students, professionals, and anyone reliant on portable computing.

One of the standout features of the AA-PWCBD-TE is its impressive capacity, designed to enhance the performance of your device. With a power capacity of around 5200 mAh, this battery is engineered to provide extended usage times, allowing users to work on the go without frequent interruptions for recharging. The battery supports efficient energy management, contributing to the overall longevity of the device.

Additionally, the AA-PWCBD-TE integrates advanced lithium-ion technology, which is favored for its reliability and minimal memory effect. Lithium-ion batteries typically offer a higher energy density compared to older technologies, meaning they can store more energy in a smaller size. This technology also supports faster charging times, making it a convenient solution for busy users.

Safety is another vital characteristic of the AA-PWCBD-TE. It features built-in protection against overcharging, overheating, and short-circuit conditions, which helps ensure the safety of both the battery and the device itself. This level of protection is crucial, especially in professional environments where equipment failure can lead to productivity losses.

Compatibility is also a key aspect of the AA-PWCBD-TE, as it is designed to fit a variety of Compaq laptop models. Users can easily determine whether this battery is suitable for their specific model, simplifying the buying process and ensuring optimal performance.

In terms of weight and dimensions, the AA-PWCBD-TE is designed to be lightweight and compact, adding minimal bulk to the laptop while still delivering powerful performance. Users can enjoy the balance of efficiency and portability, making it an ideal choice for those who travel frequently or require a battery that doesn't compromise on power.

Overall, the Compaq AA-PWCBD-TE stands out as a dependable and efficient laptop battery that enhances the user experience. With its impressive capacity, cutting-edge technology, and safety features, it is a valuable accessory for anyone looking to improve their mobile computing capabilities.
Top Page Image Contents