www.riscos.com Technical Support: Programmer's Reference Manual

ScreenBlank

Introduction and Overview

The ScreenBlank module provides the facilities needed to support screen blanking. There are two service calls so that applications can tell when the screen is blanked and when it is restored.

There is also a * Command with which you can override the default time of inactivity before the screen blanks. The default time itself is set using the Configure application; there is no defined programmers' interface to do so.

The ScreenBlank module also provides a SWI for internal use by the Portable module; you must not use it in your own code.

This module is not available in RISC OS 2.

Service Calls

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Service_ScreenBlanked
(Service Call &7A)

Screen blanked by screen blanker

On entry

R1 = &7A (reason code)

On exit

All registers must be preserved.

Use

This service call is issued by the screen blanker, after the screen has been blanked This service call should not be claimed.

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Service_ScreenRestored
(Service Call &7B)

Screen restored by screen blanker

On entry

R0 = 0, or flags passed in R4 to ScreenBlanker_Control 2
R1 = &7B (reason code)

On exit

All registers must be preserved.

Use

This service call is issued by the screen blanker, after the screen has been restored. This service call should not be claimed.

R0 is normally zero. If however the call results from a flash cycle, then it will be set to the value of R4 that was passed to ScreenBlanker_Control 2.

SWI calls

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ScreenBlanker_Control
(SWI &43100)

This SWI is for internal use by the Portable module. You must not use it in your own code.

* Commands

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*BlankTime

Sets the time of inactivity before the screen blanks

Syntax

*BlankTime [W|O] [time]

Parameters

W - writing to the screen finishes screen blanking

O - writing to the screen does not finish screen blanking

time - time of inactivity before the screen blanks

Use

*BlankTime sets the time in seconds before the screen blanks. If, during this time, there is no activity (ie no keyboard or mouse input is received, and - with the W option - there is no writing to the screen) the screen then blanks. This saves 'burn in' on the phosphor of your monitor, which occurs when the monitor consistently displays a particular image, such as the desktop.

Screen blanking finishes as soon as there is activity (see above).

If no option is specified, O is assumed.

The blank time is only retained until the next reset.

Example

*BlankTime W 600 - blanks the screen if neither input nor output occur for 10 minutes

Related commands

None

Related SWIs

None

Related vectors

WrchV (claimed by W option)