From 9f3bf608e9b300d7f5c85acf591c7e3c2a0d4f43 Mon Sep 17 00:00:00 2001
From: Frederico Linhares <fred@linhares.blue>
Date: Mon, 23 May 2022 10:38:55 -0300
Subject: feat Subdivide collision detection

* src/rect.c (cg_cRect_align_vertically, cg_cRect_align_horizontally):
Collision detection consists of two different algorithms that detect if
two boxes are aligned vertically and horizontally. Now those two
algorithms can be used separately.
---
 src/rect.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 44 insertions(+), 4 deletions(-)

diff --git a/src/rect.c b/src/rect.c
index 206ab45..52c9dd4 100644
--- a/src/rect.c
+++ b/src/rect.c
@@ -27,6 +27,18 @@ cg_free_rect(mrb_state *mrb, void* obj)
 const struct mrb_data_type cg_rect_type = {
   "CG_Rect", cg_free_rect };
 
+static inline SDL_bool
+align_vertically(int a_x, int a_width, int b_x, int b_width)
+{
+  return a_x <= b_x + b_width && a_x + a_width >= b_x;
+}
+
+static inline SDL_bool
+align_horizontally(int a_y, int a_height, int b_y, int b_height)
+{
+  return a_y <= b_y + b_height && a_y + a_height >= b_y;
+}
+
 static mrb_value
 cg_cRect_initialize(mrb_state *mrb, mrb_value self)
 {
@@ -163,6 +175,30 @@ cg_cRect_draw_fill(mrb_state *mrb, mrb_value self)
   return self;
 }
 
+static mrb_value
+cg_cRect_align_vertically(mrb_state *mrb, mrb_value self)
+{
+  struct cg_rect *ptr, *that;
+
+  mrb_get_args(mrb, "d", &that, &cg_rect_type);
+  ptr = (struct cg_rect *)DATA_PTR(self);
+
+  return mrb_bool_value(
+    align_vertically(ptr->rect.x, ptr->rect.w, that->rect.x, that->rect.w));
+}
+
+static mrb_value
+cg_cRect_align_horizontally(mrb_state *mrb, mrb_value self)
+{
+  struct cg_rect *ptr, *that;
+
+  mrb_get_args(mrb, "d", &that, &cg_rect_type);
+  ptr = (struct cg_rect *)DATA_PTR(self);
+
+  return mrb_bool_value(
+    align_horizontally(ptr->rect.y, ptr->rect.h, that->rect.y, that->rect.h));
+}
+
 static mrb_value
 cg_cRect_collide(mrb_state *mrb, mrb_value self)
 {
@@ -172,10 +208,8 @@ cg_cRect_collide(mrb_state *mrb, mrb_value self)
   ptr = (struct cg_rect *)DATA_PTR(self);
 
   return mrb_bool_value(
-    ptr->rect.x <= that->rect.x + that->rect.w &&
-    ptr->rect.x + ptr->rect.w >= that->rect.x &&
-    ptr->rect.y <= that->rect.y + that->rect.h &&
-    ptr->rect.y + ptr->rect.h >= that->rect.y);
+    align_vertically(ptr->rect.x, ptr->rect.w, that->rect.x, that->rect.w) &&
+    align_horizontally(ptr->rect.y, ptr->rect.h, that->rect.y, that->rect.h));
 }
 
 void
@@ -204,6 +238,12 @@ cg_rect_init(mrb_state *mrb)
     mrb, cg_cRect, "draw_lines", cg_cRect_draw_lines, MRB_ARGS_NONE());
   mrb_define_method(
     mrb, cg_cRect, "draw_fill", cg_cRect_draw_fill, MRB_ARGS_NONE());
+  mrb_define_method(
+    mrb, cg_cRect, "align_vertically?", cg_cRect_align_vertically,
+    MRB_ARGS_REQ(1));
+  mrb_define_method(
+    mrb, cg_cRect, "align_horizontally?", cg_cRect_align_vertically,
+    MRB_ARGS_REQ(1));
   mrb_define_method(
     mrb, cg_cRect, "collide?", cg_cRect_collide, MRB_ARGS_REQ(1));
 }
-- 
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