src/rect.c

   1 #include <string.h>
   2 #include <assert.h>
   3 #include <math.h>
   4
   5 #include <SDL2/SDL.h>
   6
   7 #include "./rect.h"
   8
   9 rect_t rect(float x, float y, float w, float h)
  10 {
  11     const rect_t result = {
  12         .x = x,
  13         .y = y,
  14         .w = w,
  15         .h = h
  16     };
  17
  18     return result;
  19 }
  20
  21 rect_t rect_from_vecs(point_t position, vec_t size)
  22 {
  23     return rect(position.x, position.y, size.x, size.y);
  24 }
  25
  26 rect_t rect_from_sdl(const SDL_Rect *rect)
  27 {
  28     const rect_t result = {
  29         .x = (float) rect->x,
  30         .y = (float) rect->y,
  31         .w = (float) rect->w,
  32         .h = (float) rect->h
  33     };
  34
  35     return result;
  36 }
  37
  38 rect_t rects_overlap_area(rect_t rect1, rect_t rect2)
  39 {
  40     float x1 = fmaxf(rect1.x, rect2.x);
  41     float y1 = fmaxf(rect1.y, rect2.y);
  42     float x2 = fminf(rect1.x + rect1.w, rect2.x + rect2.w);
  43     float y2 = fminf(rect1.y + rect1.h, rect2.y + rect2.h);
  44
  45     rect_t result = {
  46         .x = x1,
  47         .y = y1,
  48         .w = fmaxf(0.0f, x2 - x1),
  49         .h = fmaxf(0.0f, y2 - y1)
  50     };
  51     return result;
  52 }
  53
  54 int rects_overlap(rect_t rect1, rect_t rect2)
  55 {
  56     return rect1.x + rect1.w >= rect2.x
  57         && rect2.x + rect2.w >= rect1.x
  58         && rect2.y + rect2.h >= rect1.y
  59         && rect1.y + rect1.h >= rect2.y;
  60 }
  61
  62 float line_length(line_t line)
  63 {
  64     float dx = line.p1.x - line.p2.x;
  65     float dy = line.p1.y - line.p2.y;
  66     return sqrtf(dx * dx + dy * dy);
  67 }
  68
  69 void rect_object_impact(const rect_t *object,
  70                         const rect_t *obstacle,
  71                         int *sides)
  72 {
  73     assert(object);
  74     assert(obstacle);
  75     assert(sides);
  76
  77     rect_t int_area = rects_overlap_area(*object, *obstacle);
  78
  79     if (int_area.w * int_area.h > 0.0f) {
  80         for (int side = 0; side < RECT_SIDE_N; ++side) {
  81             line_t object_side = rect_side(*object, side);
  82             line_t int_side = rect_side(int_area, side);
  83
  84             if (line_length(int_side) > 10.0f) {
  85                 sides[side] = sides[side] ||
  86                     (fabs(object_side.p1.x - object_side.p2.x) < 1e-6
  87                      && fabs(object_side.p1.x - int_side.p1.x) < 1e-6
  88                      && fabs(object_side.p1.x - int_side.p2.x) < 1e-6)
  89                     || (fabs(object_side.p1.y - object_side.p2.y) < 1e-6
  90                         && fabs(object_side.p1.y - int_side.p1.y) < 1e-6
  91                         && fabs(object_side.p1.y - int_side.p2.y) < 1e-6);
  92             }
  93         }
  94     }
  95 }
  96
  97 line_t rect_side(rect_t rect, rect_side_t side)
  98 {
  99     const float x1 = rect.x;
 100     const float y1 = rect.y;
 101     const float x2 = rect.x + rect.w;
 102     const float y2 = rect.y + rect.h;
 103
 104     line_t result;
 105
 106     switch (side) {
 107     case RECT_SIDE_LEFT:
 108         result.p1.x = x1;
 109         result.p1.y = y1;
 110         result.p2.x = x1;
 111         result.p2.y = y2;
 112         break;
 113     case RECT_SIDE_RIGHT:
 114         result.p1.x = x2;
 115         result.p1.y = y1;
 116         result.p2.x = x2;
 117         result.p2.y = y2;
 118         break;
 119     case RECT_SIDE_TOP:
 120         result.p1.x = x1;
 121         result.p1.y = y1;
 122         result.p2.x = x2;
 123         result.p2.y = y1;
 124         break;
 125     case RECT_SIDE_BOTTOM:
 126         result.p1.x = x1;
 127         result.p1.y = y2;
 128         result.p2.x = x2;
 129         result.p2.y = y2;
 130         break;
 131     default: {}
 132     }
 133
 134     return result;
 135 }
 136
 137 rect_t rect_from_point(point_t p, float w, float h)
 138 {
 139     rect_t result = {
 140         .x = p.x,
 141         .y = p.y,
 142         .w = w,
 143         .h = h
 144     };
 145
 146     return result;
 147 }
 148
 149 int rect_contains_point(rect_t rect, point_t p)
 150 {
 151     return rect.x <= p.x && p.x <= rect.x + rect.w
 152         && rect.y <= p.y && p.y <= rect.y + rect.h;
 153 }
 154
 155 SDL_Rect rect_for_sdl(rect_t rect)
 156 {
 157     const SDL_Rect result = {
 158         .x = (int) roundf(rect.x),
 159         .y = (int) roundf(rect.y),
 160         .w = (int) roundf(rect.w),
 161         .h = (int) roundf(rect.h)
 162     };
 163
 164     return result;
 165 }