VDP Sprite support. More...

#include "config.h"
#include "types.h"
#include "dma.h"

Classes
struct	VDPSprite
	VDP sprite definition structure replicating VDP hardware sprite. More...
Defines
#define	SAT_MAX_SIZE 80
	Maximum size of Sprite Attribute Table (128 in VRAM but limited to 80 in VDP anyway)
#define	SPRITE_SIZE(w, h) ((((w) - 1) << 2) \| ((h) - 1))
	Helper to define sprite size in sprite definition structure.
Functions
void	VDP_resetSprites (void)
	Clear all sprites and reset VDP sprite allocation (if any).
void	VDP_releaseAllSprites (void)
	Release all VDP sprite allocation.
s16	VDP_allocateSprites (u16 num)
	Allocate the specified number of hardware VDP sprites and link them together.
void	VDP_releaseSprites (u16 index, u16 num)
	Release specified number of VDP sprites.
u16	VDP_getAvailableSprites (void)
	Returns the number of available VDP sprite from the SAT. WARNING: the SAT maximum size is 128 entries in VRAM but the VDP can only display up to 80 (H40 mode) or 64 sprites (H32 mode) at once on the screen.
s16	VDP_refreshHighestAllocatedSpriteIndex (void)
	Compute and return the highest index of currently allocated VDP sprite. A value of -1 mean no VDP Sprite are allocated. This value can be used to define the number of sprite to transfer with VDP_updateSprites(..) method.
void	VDP_clearSprites (void)
	Clear all sprites.
void	VDP_setSpriteFull (u16 index, s16 x, s16 y, u8 size, u16 attribut, u8 link)
	Set a sprite (use sprite list cache).
void	VDP_setSprite (u16 index, s16 x, s16 y, u8 size, u16 attribut)
	Set a sprite (use sprite list cache).
void	VDP_setSpritePosition (u16 index, s16 x, s16 y)
	Set sprite position (use sprite list cache).
void	VDP_setSpriteSize (u16 index, u8 size)
	Set sprite size (use sprite list cache).
void	VDP_setSpriteAttribut (u16 index, u16 attribut)
	Set sprite attributes (use sprite list cache).
void	VDP_setSpriteLink (u16 index, u8 link)
	Set sprite link (use sprite list cache).
VDPSprite *	VDP_linkSprites (u16 index, u16 num)
	Link sprites starting at the specified index. Links are created in simple ascending order (1 --> 2 --> 3 --> ...)
void	VDP_updateSprites (u16 num, TransferMethod tm)
	Send the cached sprite list to the VDP.
void	VDP_setSpritePriority (u16 index, bool priority)
	Set sprite priority (use sprite list cache).
bool	VDP_getSpritePriority (u16 index)
	Get sprite priority (use sprite list cache).
void	VDP_setSpritePalette (u16 index, u16 palette)
	Set sprite palette (use sprite list cache).
u16	VDP_getSpritePalette (u16 index)
	Get sprite palette (use sprite list cache).
void	VDP_setSpriteFlip (u16 index, bool flipH, bool flipV)
	Set sprite horizontal and vertical flip (use sprite list cache).
void	VDP_setSpriteFlipH (u16 index, bool flipH)
	Set sprite horizontal flip (use sprite list cache).
void	VDP_setSpriteFlipV (u16 index, bool flipV)
	Set sprite vertical flip (use sprite list cache).
bool	VDP_getSpriteFlipH (u16 index)
	Get sprite horizontal flip (use sprite list cache).
bool	VDP_getSpriteFlipV (u16 index)
	Get sprite vertical flip (use sprite list cache).
void	VDP_setSpriteTile (u16 index, u16 tile)
	Set sprite tile index (use sprite list cache).
u16	VDP_getSpriteTile (u16 index)
	Get sprite tile index (use sprite list cache).
Variables
VDPSprite	vdpSpriteCache [SAT_MAX_SIZE+16]
	VDP sprite cache.
VDPSprite *	lastAllocatedVDPSprite
	Pointer to last allocated sprite after calling VDP_allocateSprites(..) method. This can be used to do the link from the last allocated VDP sprite.
s16	highestVDPSpriteIndex
	Highest index of allocated VDP sprite since the last call to VDP_resetSprites() or VDP_releaseAllSprites(). A value of -1 mean no VDP Sprite were allocated.. This can be used to define the number of sprite to transfer with VDP_updateSprites(..) method. WARNING: this value is not correctly updated on sprite release operation so it may gives an higher index than reality. You can ue currently VDP_refreshHighestAllocatedSpriteIndex() method to force recomputation of highest index (costs a bit of time).

Detailed Description

VDP Sprite support.

Author:: Stephane Dallongeville

Date:: 08/2011

This unit provides methods to allocate and manipulate VDP Sprite at low level.
The Sega Genesis VDP can handle up to 80 simultanous sprites of 4x4 tiles (32x32 pixels).

Define Documentation

#define SPRITE_SIZE	(	w,
		h
	)	((((w) - 1) << 2) \| ((h) - 1))

Helper to define sprite size in sprite definition structure.

Parameters:

w	sprite width (in tile).
h	sprite height (in tile).

Function Documentation

s16 VDP_allocateSprites ( u16 num )

Allocate the specified number of hardware VDP sprites and link them together.

Parameters:

num	Number of VDP sprite to allocate (need to be > 0)

Returns:: the first VDP sprite index where allocation was made.
-1 if there is not enough available VDP sprite remaining.
WARNING: VDP can display up to 80 sprites at once on screen in H40 mode only, in H32 mode it's limited to 64 sprites even if we allow to allocate up to 80 (SAT size).

This method allocates the specified number of VDP sprite and returns the index of the first allocated sprite in VDP sprite table (see vdpSpriteCache).
Sprites are linked together using link field (last sprite ends with link 0).
If there is not enough available VDP sprites the allocation operation fails and return -1. NOTE: The last sprite from the allocated list can be retrieved with lastAllocatedVDPSprite, this is to avoid parsing all the list to find it, if we want to link it to a specific sprite for instance.

See also:: VDP_releaseSprites(..)

u16 VDP_getAvailableSprites ( void )

Returns the number of available VDP sprite from the SAT. WARNING: the SAT maximum size is 128 entries in VRAM but the VDP can only display up to 80 (H40 mode) or 64 sprites (H32 mode) at once on the screen.

See also:: VDP_allocateSprites(..); VDP_releaseSprites(..)

bool VDP_getSpriteFlipH ( u16 index )

Get sprite horizontal flip (use sprite list cache).

Parameters: