Drag A Sprite

Contents

• Introduction
• SWI calls
  • DragASprite_Start
  • DragASprite_Stop

Introduction

The DragASprite module provides SWI calls with which you can make the pointer drag a sprite around the screen. Since not all users will prefer this effect to dragging an outline - whether for aesthetics or performance - there is a bit in the CMOS RAM used to indicate their preference. (See the chapter entitled Non-volatile memory (CMOS RAM).) You should examine that bit before using this module; if it shows that the user would prefer to drag outlines, oblige them!

To drag a sprite:

1. Prepare a sprite to be dragged (this may be trivial, as the application may have a suitable sprite already to hand).
2. Call the SWI DragASprite_Start. This takes a copy of your sprite - so you can dispose of your copy whenever you like - and then starts a Wimp drag.
3. When the Wimp sends you an indication that your drag has finished, you should call the SWI DragASprite_Stop to release the workspace used for the drag.

SWI calls

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DragASprite_Start
(SWI &42400)

Start a sprite drag operation

On entry

R0	=	flags : Bit(s) Meaning 0 - 1 Horizontal location of sprite in box: Bit(s) Meaning 00 left 01 centre 10 right 2 - 3 Vertical location of sprite in box: Bit(s) Meaning 00 bottom 01 centre 10 top 4 - 5 Drag bounding box is: Bit(s) Meaning 00 whole screen 01 display area of window that the pointer's over 10 specified in block pointed to by R4 6 Bounding box applies to: Bit(s) Meaning 0 the box 1 the pointer 7 Control of drop-shadow: Bit(s) Meaning 0 don't do a drop-shadow 1 make a drop shadow when copying the sprite 8 Control of translucency (just cross-hatching in current version): Bit(s) Meaning 0 dragged sprite will be translucent 1 dragged sprite will be solid 9 Control of sprite centering: Bit(s) Meaning 0 sprite position is determined by bits 0 - 3 1 sprite will be centered on the pointer 10 - 31 Reserved for future use - should be set to 0
R1	=	sprite area holding sprite: Value Meaning 0 system sprite area 1 wimp sprite area Other address of sprite area
R2	=	pointer to sprite name
R3	=	pointer to 16-byte block containing box
R4	=	pointer to optional 16-byte block containing bounding box (see flags)

On exit

R0-4

preserved

Interrupts

Interrupts are undefined
Fast interrupts are enabled

Processor mode

Processor is in SVC mode

Re-entrancy

Not defined

Use

This call starts dragging a sprite. The sprite you supply is copied, so there is no problem if you dispose of your copy of the sprite. If there is insufficient memory available to start the drag, the call reverts to a normal drag of a dotted outline.

The blocks pointed to by R3 and - optionally - R4 have the following format:

Offset	Use
+0	x-low
+4	y-low	bottom-left (x-low, y-low) is inclusive
+8	x-high	top-right (x-high, y-high) is exclusive
+12	y-high

Related SWIs

DragASprite_Stop

Document information

Maintainer(s):	RISCOS Ltd <developer@riscos.com>
History:	Revision Date Author Changes 1 ROL Initial version
Disclaimer:	Copyright © Pace Micro Technolgy plc, 2002. Portions copyright © RISCOS Ltd, 2002. Published by RISCOS Limited. No part of this publication may be reproduced or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, or stored in any retrieval system of any nature, without the written permission of the copyright holder and the publisher, application for which shall be made to the publisher.