scroll.h

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#ifndef ALCHEMY_SCROLL_H
#define ALCHEMY_SCROLL_H
 
/// @file
/// The display scroll work, the HBlank scroll work and its wave.
 
#include "map_scroll.h"
#include "static_assert.h"
 
/// The wavy background's work: two pages of BG1 to BG3 scroll offsets for each
/// of the 160 scanlines, and the sine wave that bends them on each axis.
struct DisplayScrollWork {
  struct BgScroll rows[2][160][3]; ///< per page and scanline: BG3, BG2, BG1
  u8 page;      ///< the page the HBlank DMA shows; the other is built
  u8 mode;      ///< set at the start; not read by name
  u16 frame;    ///< frames built so far, added to BG3's y for the wave's phase
  u8 unkf04[4]; ///< not named by TBS code
  s32 freqX;    ///< phase per frame and per BG3 row, 16.16 wave table entries
  s32 freqY;    ///< phase per frame and per BG3 row, 16.16 wave table entries
  s32 stepX;    ///< 16.16 wave table entries a scanline, 256 a cycle
  s32 stepY;    ///< 16.16 wave table entries a scanline, 256 a cycle
  s32 ampX;     ///< 16.16 scale on the sine entry, which is then divided by 256
  s32 ampY;     ///< 16.16 scale on the sine entry, which is then divided by 256
};
 
STATIC_ASSERT(sizeof(struct DisplayScrollWork) == 0xf20);
STATIC_ASSERT(offsetof(struct DisplayScrollWork, page) == 0xf00);
STATIC_ASSERT(offsetof(struct DisplayScrollWork, freqX) == 0xf08);
 
extern struct DisplayScrollWork *gHBlankScrollWork;
extern const s16 gDisplayScroll_WaveSine[];
 
#endif