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