src/rect.c

   1 #include <string.h>
   2 #include <assert.h>
   3 #include <math.h>
   4 #include "./rect.h"
   5
   6 rect_t rect_int_area(rect_t rect1, rect_t rect2)
   7 {
   8     float x1 = fmaxf(rect1.x, rect2.x);
   9     float y1 = fmaxf(rect1.y, rect2.y);
  10     float x2 = fminf(rect1.x + rect1.w, rect2.x + rect2.w);
  11     float y2 = fminf(rect1.y + rect1.h, rect2.y + rect2.h);
  12
  13     rect_t result = {
  14         .x = x1,
  15         .y = y1,
  16         .w = fmaxf(0.0f, x2 - x1),
  17         .h = fmaxf(0.0f, y2 - y1)
  18     };
  19     return result;
  20 }
  21
  22 int is_rect_int(rect_t rect1, rect_t rect2)
  23 {
  24     rect_t int_area = rect_int_area(rect1, rect2);
  25     return int_area.w * int_area.h > 0.0f;
  26 }
  27
  28 float line_length(line_t line)
  29 {
  30     float dx = line.p1.x - line.p2.x;
  31     float dy = line.p1.y - line.p2.y;
  32     return sqrtf(dx * dx + dy * dy);
  33 }
  34
  35 void rect_object_impact(const rect_t *object,
  36                         const rect_t *obstacle,
  37                         int *sides)
  38 {
  39     assert(object);
  40     assert(obstacle);
  41     assert(sides);
  42
  43     rect_t int_area = rect_int_area(*object, *obstacle);
  44
  45     if (int_area.w * int_area.h > 0.0f) {
  46         for (int side = 0; side < RECT_SIDE_N; ++side) {
  47             line_t object_side = rect_side(*object, side);
  48             line_t int_side = rect_side(int_area, side);
  49
  50             if (line_length(int_side) > 10.0f) {
  51                 sides[side] = sides[side] ||
  52                     (fabs(object_side.p1.x - object_side.p2.x) < 1e-6
  53                      && fabs(object_side.p1.x - int_side.p1.x) < 1e-6
  54                      && fabs(object_side.p1.x - int_side.p2.x) < 1e-6)
  55                     || (fabs(object_side.p1.y - object_side.p2.y) < 1e-6
  56                         && fabs(object_side.p1.y - int_side.p1.y) < 1e-6
  57                         && fabs(object_side.p1.y - int_side.p2.y) < 1e-6);
  58             }
  59         }
  60     }
  61 }
  62
  63 line_t rect_side(rect_t rect, rect_side_t side)
  64 {
  65     const float x1 = rect.x;
  66     const float y1 = rect.y;
  67     const float x2 = rect.x + rect.w;
  68     const float y2 = rect.y + rect.h;
  69
  70     line_t result;
  71
  72     switch (side) {
  73     case RECT_SIDE_LEFT:
  74         result.p1.x = x1;
  75         result.p1.y = y1;
  76         result.p2.x = x1;
  77         result.p2.y = y2;
  78         break;
  79     case RECT_SIDE_RIGHT:
  80         result.p1.x = x2;
  81         result.p1.y = y1;
  82         result.p2.x = x2;
  83         result.p2.y = y2;
  84         break;
  85     case RECT_SIDE_TOP:
  86         result.p1.x = x1;
  87         result.p1.y = y1;
  88         result.p2.x = x2;
  89         result.p2.y = y1;
  90         break;
  91     case RECT_SIDE_BOTTOM:
  92         result.p1.x = x1;
  93         result.p1.y = y2;
  94         result.p2.x = x2;
  95         result.p2.y = y2;
  96         break;
  97     default: {}
  98     }
  99
 100     return result;
 101 }
 102
 103 rect_t rect_from_point(point_t p, float w, float h)
 104 {
 105     rect_t result = {
 106         .x = p.x,
 107         .y = p.y,
 108         .w = w,
 109         .h = h
 110     };
 111
 112     return result;
 113 }