text: /*************************************************************************/
  /*  collision_polygon_2d.cpp                                             */
  /*************************************************************************/
  /*                       This file is part of:                           */
  /*                           GODOT ENGINE                                */
  /*                      https://godotengine.org                          */
  /*************************************************************************/
  /* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
  /* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
  /*                                                                       */
  /* Permission is hereby granted, free of charge, to any person obtaining */
  /* a copy of this software and associated documentation files (the       */
  /* "Software"), to deal in the Software without restriction, including   */
  /* without limitation the rights to use, copy, modify, merge, publish,   */
  /* distribute, sublicense, and/or sell copies of the Software, and to    */
  /* permit persons to whom the Software is furnished to do so, subject to */
  /* the following conditions:                                             */
  /*                                                                       */
  /* The above copyright notice and this permission notice shall be        */
  /* included in all copies or substantial portions of the Software.       */
  /*                                                                       */
  /* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,       */
  /* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF    */
  /* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.*/
  /* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY  */
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  /* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
  /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
  /*************************************************************************/
  
  #include "collision_polygon_2d.h"
  
  #include "collision_object_2d.h"
  #include "core/engine.h"
  #include "core/math/geometry_2d.h"
  #include "scene/resources/concave_polygon_shape_2d.h"
  #include "scene/resources/convex_polygon_shape_2d.h"
  
  #include "thirdparty/misc/triangulator.h"
  
  void CollisionPolygon2D::_build_polygon() {
  	parent->shape_owner_clear_shapes(owner_id);
  
  	if (polygon.size() == 0) {
  		return;
  	}
  
  	bool solids = build_mode == BUILD_SOLIDS;
  
  	if (solids) {
  		//here comes the sun, lalalala
  		//decompose concave into multiple convex polygons and add them
  		Vector<Vector<Vector2>> decomp = _decompose_in_convex();
  		for (int i = 0; i < decomp.size(); i++) {
  			Ref<ConvexPolygonShape2D> convex = memnew(ConvexPolygonShape2D);
  			convex->set_points(decomp[i]);
  			parent->shape_owner_add_shape(owner_id, convex);
  		}
  
  	} else {
  		Ref<ConcavePolygonShape2D> concave = memnew(ConcavePolygonShape2D);
  
  		Vector<Vector2> segments;
  		segments.resize(polygon.size() * 2);
  		Vector2 *w = segments.ptrw();
  
  		for (int i = 0; i < polygon.size(); i++) {
  			w[(i << 1) + 0] = polygon[i];
  			w[(i << 1) + 1] = polygon[(i + 1) % polygon.size()];
  		}
  
  		concave->set_segments(segments);
  
  		parent->shape_owner_add_shape(owner_id, concave);
  	}
  }
  
  Vector<Vector<Vector2>> CollisionPolygon2D::_decompose_in_convex() {
  	Vector<Vector<Vector2>> decomp = Geometry2D::decompose_polygon_in_convex(polygon);
  	return decomp;
  }
  
  void CollisionPolygon2D::_update_in_shape_owner(bool p_xform_only) {
  	parent->shape_owner_set_transform(owner_id, get_transform());
  	if (p_xform_only) {
  		return;
  	}
  	parent->shape_owner_set_disabled(owner_id, disabled);
  	parent->shape_owner_set_one_way_collision(owner_id, one_way_collision);
  	parent->shape_owner_set_one_way_collision_margin(owner_id, one_way_collision_margin);
  }
  
  void CollisionPolygon2D::_notification(int p_what) {
  	switch (p_what) {
  		case NOTIFICATION_PARENTED: {
  			parent = Object::cast_to<CollisionObject2D>(get_parent());
  			if (parent) {
  				owner_id = parent->create_shape_owner(this);
  				_build_polygon();
  				_update_in_shape_owner();
  			}
  
  			/*if (Engine::get_singleton()->is_editor_hint()) {
  				//display above all else
  				set_z_as_relative(false);
  				set_z_index(RS::CANVAS_ITEM_Z_MAX - 1);
  			}*/
  
  		} break;
  		case NOTIFICATION_ENTER_TREE: {
  			if (parent) {
  				_update_in_shape_owner();
  			}
  
  		} break;
  		case NOTIFICATION_LOCAL_TRANSFORM_CHANGED: {
  			if (parent) {
  				_update_in_shape_owner(true);
  			}
  
  		} break;
  		case NOTIFICATION_UNPARENTED: {
  			if (parent) {
  				parent->remove_shape_owner(owner_id);
  			}
  			owner_id = 0;
  			parent = nullptr;
  		} break;
  
  		case NOTIFICATION_DRAW: {
  			if (!Engine::get_singleton()->is_editor_hint() && !get_tree()->is_debugging_collisions_hint()) {
  				break;
  			}
  
  			for (int i = 0; i < polygon.size(); i++) {
  				Vector2 p = polygon[i];
  				Vector2 n = polygon[(i + 1) % polygon.size()];
  				// draw line with width <= 1, so it does not scale with zoom and break pixel exact editing
  				draw_line(p, n, Color(0.9, 0.2, 0.0, 0.8), 1);
  			}
  #define DEBUG_DECOMPOSE
  #if defined(TOOLS_ENABLED) && defined(DEBUG_DECOMPOSE)
  
  			Vector<Vector<Vector2>> decomp = _decompose_in_convex();
  
  			Color c(0.4, 0.9, 0.1);
  			for (int i = 0; i < decomp.size(); i++) {
  				c.set_hsv(Math::fmod(c.get_h() + 0.738, 1), c.get_s(), c.get_v(), 0.5);
  				draw_colored_polygon(decomp[i], c);
  			}
  #else
  			draw_colored_polygon(polygon, get_tree()->get_debug_collisions_color());
  #endif
  
  			if (one_way_collision) {
  				Color dcol = get_tree()->get_debug_collisions_color(); //0.9,0.2,0.2,0.4);
  				dcol.a = 1.0;
  				Vector2 line_to(0, 20);
  				draw_line(Vector2(), line_to, dcol, 3);
  				Vector<Vector2> pts;
  				float tsize = 8;
  				pts.push_back(line_to + (Vector2(0, tsize)));
  				pts.push_back(line_to + (Vector2(Math_SQRT12 * tsize, 0)));
  				pts.push_back(line_to + (Vector2(-Math_SQRT12 * tsize, 0)));
  				Vector<Color> cols;
  				for (int i = 0; i < 3; i++) {
  					cols.push_back(dcol);
  				}
  
  				draw_primitive(pts, cols, Vector<Vector2>()); //small arrow
  			}
  		} break;
  	}
  }
  
  void CollisionPolygon2D::set_polygon(const Vector<Point2> &p_polygon) {
  	polygon = p_polygon;
  
  	{
  		for (int i = 0; i < polygon.size(); i++) {
  			if (i == 0) {
  				aabb = Rect2(polygon[i], Size2());
  			} else {
  				aabb.expand_to(polygon[i]);
  			}
  		}
  		if (aabb == Rect2()) {
  			aabb = Rect2(-10, -10, 20, 20);
  		} else {
  			aabb.position -= aabb.size * 0.3;
  			aabb.size += aabb.size * 0.6;
  		}
  	}
  
  	if (parent) {
  		_build_polygon();
  	}
  	update();
  	update_configuration_warning();
  }
  
  Vector<Point2> CollisionPolygon2D::get_polygon() const {
  	return polygon;
  }
  
  void CollisionPolygon2D::set_build_mode(BuildMode p_mode) {
  	ERR_FAIL_INDEX((int)p_mode, 2);
  	build_mode = p_mode;
  	if (parent) {
  		_build_polygon();
  	}
  }
  
  CollisionPolygon2D::BuildMode CollisionPolygon2D::get_build_mode() const {
  	return build_mode;
  }
  
  #ifdef TOOLS_ENABLED
  Rect2 CollisionPolygon2D::_edit_get_rect() const {
  	return aabb;
  }
  
  bool CollisionPolygon2D::_edit_use_rect() const {
  	return true;
  }
  
  bool CollisionPolygon2D::_edit_is_selected_on_click(const Point2 &p_point, double p_tolerance) const {
  	return Geometry2D::is_point_in_polygon(p_point, Variant(polygon));
  }
  #endif
  
  String CollisionPolygon2D::get_configuration_warning() const {
  	if (!Object::cast_to<CollisionObject2D>(get_parent())) {
  		return TTR("CollisionPolygon2D only serves to provide a collision shape to a CollisionObject2D derived node. Please only use it as a child of Area2D, StaticBody2D, RigidBody2D, KinematicBody2D, etc. to give them a shape.");
  	}
  
  	if (polygon.empty()) {
  		return TTR("An empty CollisionPolygon2D has no effect on collision.");
  	}
  
  	return String();
  }
  
  void CollisionPolygon2D::set_disabled(bool p_disabled) {
  	disabled = p_disabled;
  	update();
  	if (parent) {
  		parent->shape_owner_set_disabled(owner_id, p_disabled);
  	}
  }
  
  bool CollisionPolygon2D::is_disabled() const {
  	return disabled;
  }
  
  void CollisionPolygon2D::set_one_way_collision(bool p_enable) {
  	one_way_collision = p_enable;
  	update();
  	if (parent) {
  		parent->shape_owner_set_one_way_collision(owner_id, p_enable);
  	}
  }
  
  bool CollisionPolygon2D::is_one_way_collision_enabled() const {
  	return one_way_collision;
  }
  
  void CollisionPolygon2D::set_one_way_collision_margin(float p_margin) {
  	one_way_collision_margin = p_margin;
  	if (parent) {
  		parent->shape_owner_set_one_way_collision_margin(owner_id, one_way_collision_margin);
  	}
  }
  
  float CollisionPolygon2D::get_one_way_collision_margin() const {
  	return one_way_collision_margin;
  }
  
  void CollisionPolygon2D::_bind_methods() {
  	ClassDB::bind_method(D_METHOD("set_polygon", "polygon"), &CollisionPolygon2D::set_polygon);
  	ClassDB::bind_method(D_METHOD("get_polygon"), &CollisionPolygon2D::get_polygon);
  
  	ClassDB::bind_method(D_METHOD("set_build_mode", "build_mode"), &CollisionPolygon2D::set_build_mode);
  	ClassDB::bind_method(D_METHOD("get_build_mode"), &CollisionPolygon2D::get_build_mode);
  	ClassDB::bind_method(D_METHOD("set_disabled", "disabled"), &CollisionPolygon2D::set_disabled);
  	ClassDB::bind_method(D_METHOD("is_disabled"), &CollisionPolygon2D::is_disabled);
  	ClassDB::bind_method(D_METHOD("set_one_way_collision", "enabled"), &CollisionPolygon2D::set_one_way_collision);
  	ClassDB::bind_method(D_METHOD("is_one_way_collision_enabled"), &CollisionPolygon2D::is_one_way_collision_enabled);
  	ClassDB::bind_method(D_METHOD("set_one_way_collision_margin", "margin"), &CollisionPolygon2D::set_one_way_collision_margin);
  	ClassDB::bind_method(D_METHOD("get_one_way_collision_margin"), &CollisionPolygon2D::get_one_way_collision_margin);
  
  	ADD_PROPERTY(PropertyInfo(Variant::INT, "build_mode", PROPERTY_HINT_ENUM, "Solids,Segments"), "set_build_mode", "get_build_mode");
  	ADD_PROPERTY(PropertyInfo(Variant::PACKED_VECTOR2_ARRAY, "polygon"), "set_polygon", "get_polygon");
  	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "disabled"), "set_disabled", "is_disabled");
  	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "one_way_collision"), "set_one_way_collision", "is_one_way_collision_enabled");
  	ADD_PROPERTY(PropertyInfo(Variant::FLOAT, "one_way_collision_margin", PROPERTY_HINT_RANGE, "0,128,0.1"), "set_one_way_collision_margin", "get_one_way_collision_margin");
  
  	BIND_ENUM_CONSTANT(BUILD_SOLIDS);
  	BIND_ENUM_CONSTANT(BUILD_SEGMENTS);
  }
  
  CollisionPolygon2D::CollisionPolygon2D() {
  	aabb = Rect2(-10, -10, 20, 20);
  	build_mode = BUILD_SOLIDS;
  	set_notify_local_transform(true);
  	parent = nullptr;
  	owner_id = 0;
  	disabled = false;
  	one_way_collision = false;
  	one_way_collision_margin = 1.0;
  }
  