effect_step.h

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#ifndef ALCHEMY_EFFECT_STEP_H
#define ALCHEMY_EFFECT_STEP_H
 
/// @file
/// EffectStep and EffectPosition, the positions effects move through.
 
#include "edition.h"
#include "types.h"
#include "static_assert.h"
 
/// A moving point of an effect: its position, its velocity and a value each
/// effect uses its own way (a size, a timer, -1 for idle).
struct EffectStep {
#ifdef UBFIX
  union {
    struct {
      s32 x; ///< 16.16 fixed-point pixels
      s32 y; ///< 16.16 fixed-point pixels
      s32 z; ///< 16.16 fixed-point pixels
    };
    s32 coordinates[3];
  };
#else
  s32 x; ///< 16.16 fixed-point pixels
  s32 y; ///< 16.16 fixed-point pixels
  s32 z; ///< 16.16 fixed-point pixels
#endif
  s32 velocityX; ///< 16.16 fixed-point pixels per frame
  s32 velocityY; ///< 16.16 fixed-point pixels per frame
  s32 velocityZ; ///< 16.16 fixed-point pixels per frame
  s32 variant;   ///< each effect's own: a size, a countdown, -1 for idle
};
 
/// Returns the step's three coordinates as an array.
// UB: indexing from &x crosses the step's separate scalar members. UBFIX
// supplies a real coordinate array without including motion state.
static inline const s32 *EffectStep_Coordinates(const struct EffectStep *step) {
#ifdef UBFIX
  return step->coordinates;
#else
  return &step->x;
#endif
}
 
/// A point projected onto the screen, with its depth.
struct EffectPosition {
#ifdef UBFIX
  /// Projection writes three coordinates; effects read their named components.
  union {
    struct {
      s32 x;     ///< screen pixels
      s32 y;     ///< screen pixels
      s32 depth; ///< projected depth, larger further away
    };
    s32 coordinates[3];
  };
#else
  s32 x;     ///< screen pixels
  s32 y;     ///< screen pixels
  s32 depth; ///< projected depth, larger further away
#endif
};
 
/// Returns the position's three coordinates as an array.
// UB: indexing from &x crosses separate scalar members in the legacy record.
// UBFIX provides a real array while keeping the effects' named coordinates. An
// always-on union changes native alias analysis in the effect/window code.
static inline s32 *EffectPosition_Coordinates(struct EffectPosition *position) {
#ifdef UBFIX
  return position->coordinates;
#else
  return &position->x;
#endif
}
 
STATIC_ASSERT(offsetof(struct EffectStep, x) == 0x00);
STATIC_ASSERT(offsetof(struct EffectStep, y) == 0x04);
STATIC_ASSERT(offsetof(struct EffectStep, z) == 0x08);
STATIC_ASSERT(offsetof(struct EffectStep, velocityX) == 0x0c);
STATIC_ASSERT(offsetof(struct EffectStep, velocityY) == 0x10);
STATIC_ASSERT(offsetof(struct EffectStep, velocityZ) == 0x14);
STATIC_ASSERT(offsetof(struct EffectStep, variant) == 0x18);
STATIC_ASSERT(sizeof(struct EffectStep) == 0x1c);
STATIC_ASSERT(sizeof(struct EffectPosition) == 0x0c);
 
#endif