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

Drag A Sprite

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

---

DragASprite_Start
(SWI &42400)

On entry

R0 = flags
R1 = sprite area holding sprite:

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 - R4 preserved

Interrupts

Interrupt status is 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 flags given in R0 have the following meanings:

Bits	Meaning
0 - 1	Horizontal location of sprite in box:
	00	left
	01	centre
	10	right
2 - 3	Vertical location of sprite in box:
	00	bottom
	01	centre
	10	top
4 - 5	Drag bounding box is:
	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:
	0	the box
	1	the pointer
7	Control of drop-shadow:
	0	don't do a drop-shadow
	1	make a drop shadow when copying the sprite
8 - 31	Reserved for future use - should be set to 0

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

Offset	Use
0	x-low	box
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

Related vectors

None

---

DragASprite_Stop
(SWI &42401)

Terminates any current drag operation, and releases workspace

On entry

--

On exit

--

Interrupts

Interrupt status is undefined
Fast interrupts are enabled

Processor mode

Processor is in SVC mode

Re-entrancy

Not defined

Use

This call terminates any current drag operation, and releases any workspace claimed by the DragASprite module to do a drag. You should make this call when your application receives the User_Drag_Box reason code from Wimp_Poll (see Wimp_Poll) during a drag.

Related SWIs

DragASprite_Start

Related vectors

None