rgn1.h

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/*
 * SPDX-FileCopyrightText: 2025, Roy Ratcliffe, Northumberland, United Kingdom
 * SPDX-License-Identifier: MIT
 */
#ifndef __BLIT_RGN1_H__
#define __BLIT_RGN1_H__
 
#include <assert.h>
#include <stdbool.h>
 
struct blit_rgn1 {
  int origin;
  int extent;
  int origin_source;
};
 
static inline void blit_rgn1_norm(struct blit_rgn1 *rgn1) {
  /*
   * Normalise the extents. Extents are normally positive. A negative extent
   * means the destination and source origins specify the far edge of the
   * rectangle. Two's-complement negative extents and put the origins at the
   * rectangle's origins.
   */
  if (rgn1->extent < 0) {
    rgn1->extent = -rgn1->extent;
    rgn1->origin -= rgn1->extent;
    rgn1->origin_source -= rgn1->extent;
  }
  assert(rgn1->extent >= 0);
}
 
static inline bool blit_rgn1_slip(struct blit_rgn1 *rgn1) {
  int offset = rgn1->origin < 0
                   ? (rgn1->origin < rgn1->origin_source ? -rgn1->origin
                                                         : -rgn1->origin_source)
                   : (rgn1->origin_source < 0 ? -rgn1->origin_source : 0);
  assert(offset >= 0);
  if (offset >= rgn1->extent)
    return false;
  rgn1->origin += offset;
  rgn1->origin_source += offset;
  rgn1->extent -= offset;
  assert(rgn1->origin >= 0 && rgn1->origin_source >= 0 && 0 < rgn1->extent);
  return true;
}
 
static inline bool blit_rgn1_clip(struct blit_rgn1 *rgn1, int extent) {
  if (0 >= extent)
    return false;
  if (extent < rgn1->extent)
    rgn1->extent = extent;
  return true;
}
 
#endif /* __BLIT_RGN1_H__ */