colormath.h

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#ifndef OPENSNES_COLORMATH_H
#define OPENSNES_COLORMATH_H
 
#include <snes/types.h>
#include <snes/registers.h>  /* REG_CGWSEL / REG_CGADSUB / REG_COLDATA */
 
/*============================================================================
 * Layer Masks (for colorMathEnable)
 *============================================================================*/

#define COLORMATH_BG1       BIT(0)

#define COLORMATH_BG2       BIT(1)

#define COLORMATH_BG3       BIT(2)

#define COLORMATH_BG4       BIT(3)

#define COLORMATH_OBJ       BIT(4)

#define COLORMATH_BACKDROP  BIT(5)

#define COLORMATH_ALL       0x3F
 
/*============================================================================
 * Color Math Operations
 *============================================================================*/

#define COLORMATH_ADD       0

#define COLORMATH_SUB       1
 
/*============================================================================
 * Color Math Source
 *============================================================================*/

#define COLORMATH_SRC_SUBSCREEN 0

#define COLORMATH_SRC_FIXED     1
 
/*============================================================================
 * Color Math Enable Conditions
 *============================================================================*/

#define COLORMATH_ALWAYS    0

#define COLORMATH_INSIDE    1

#define COLORMATH_OUTSIDE   2

#define COLORMATH_NEVER     3
 
/*============================================================================
 * Fixed Color Channel Masks
 *============================================================================*/

#define COLDATA_RED     0x20

#define COLDATA_GREEN   0x40

#define COLDATA_BLUE    0x80

#define COLDATA_ALL     (COLDATA_RED | COLDATA_GREEN | COLDATA_BLUE)
 
/*============================================================================
 * Core Color Math Functions
 *============================================================================*/
 
/* Internal state, exposed for the inline init/disable bodies below.
 * cgwsel + cgadsub shadow the corresponding hardware registers (which
 * are write-only). User code should manipulate via the colorMath* API,
 * not direct writes. */
extern u8 cgwsel;
extern u8 cgadsub;

inline void colorMathInit(void) {
    cgwsel = 0;
    cgadsub = 0;
    REG_CGWSEL = 0;
    REG_CGADSUB = 0;
    REG_COLDATA = 0;
}

inline void colorMathEnable(u8 layers) {
    /* Set layer enable bits (bits 0-5 of CGADSUB) */
    cgadsub = (cgadsub & 0xC0) | (layers & 0x3F);
    REG_CGADSUB = cgadsub;
}

inline void colorMathDisable(void) {
    cgadsub &= 0xC0;  /* Clear layer bits */
    REG_CGADSUB = cgadsub;
}

void colorMathSetOp(u8 op);

void colorMathSetHalf(u8 enable);

void colorMathSetSource(u8 source);

void colorMathSetCondition(u8 condition);

void colorMathSetDirectColor(u8 enable);

void colorMathSetFixedColor(u8 r, u8 g, u8 b);

void colorMathSetChannel(u8 channel, u8 intensity);
 
/*============================================================================
 * Color Math Effect Helpers
 *============================================================================*/

void colorMathTransparency50(u8 layers);

void colorMathShadow(u8 layers, u8 intensity);

void colorMathTint(u8 layers, u8 r, u8 g, u8 b);

void colorMathSetBrightness(u8 brightness);
 
#endif /* OPENSNES_COLORMATH_H */