text: /*************************************************************************/
  /*  path_2d.cpp                                                          */
  /*************************************************************************/
  /*                       This file is part of:                           */
  /*                           GODOT ENGINE                                */
  /*                      https://godotengine.org                          */
  /*************************************************************************/
  /* Copyright (c) 2007-2022 Juan Linietsky, Ariel Manzur.                 */
  /* Copyright (c) 2014-2022 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  */
  /* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,  */
  /* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE     */
  /* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.                */
  /*************************************************************************/
  
  #include "path_2d.h"
  
  #include "core/engine.h"
  #include "scene/scene_string_names.h"
  
  #ifdef TOOLS_ENABLED
  #include "editor/editor_scale.h"
  #endif
  
  #ifdef TOOLS_ENABLED
  Rect2 Path2D::_edit_get_rect() const {
  	if (!curve.is_valid() || curve->get_point_count() == 0) {
  		return Rect2(0, 0, 0, 0);
  	}
  
  	Rect2 aabb = Rect2(curve->get_point_position(0), Vector2(0, 0));
  
  	for (int i = 0; i < curve->get_point_count(); i++) {
  		for (int j = 0; j <= 8; j++) {
  			real_t frac = j / 8.0;
  			Vector2 p = curve->interpolate(i, frac);
  			aabb.expand_to(p);
  		}
  	}
  
  	return aabb;
  }
  
  bool Path2D::_edit_use_rect() const {
  	return curve.is_valid() && curve->get_point_count() != 0;
  }
  
  bool Path2D::_edit_is_selected_on_click(const Point2 &p_point, double p_tolerance) const {
  	if (curve.is_null()) {
  		return false;
  	}
  
  	for (int i = 0; i < curve->get_point_count(); i++) {
  		Vector2 s[2];
  		s[0] = curve->get_point_position(i);
  
  		for (int j = 1; j <= 8; j++) {
  			real_t frac = j / 8.0;
  			s[1] = curve->interpolate(i, frac);
  
  			Vector2 p = Geometry::get_closest_point_to_segment_2d(p_point, s);
  			if (p.distance_to(p_point) <= p_tolerance) {
  				return true;
  			}
  
  			s[0] = s[1];
  		}
  	}
  
  	return false;
  }
  #endif
  
  void Path2D::_notification(int p_what) {
  	if (p_what == NOTIFICATION_DRAW && curve.is_valid()) {
  		//draw the curve!!
  
  		if (!Engine::get_singleton()->is_editor_hint() && !get_tree()->is_debugging_navigation_hint()) {
  			return;
  		}
  
  #ifdef TOOLS_ENABLED
  		const float line_width = 2 * EDSCALE;
  #else
  		const float line_width = 2;
  #endif
  		const Color color = Color(1.0, 1.0, 1.0, 1.0);
  
  		for (int i = 0; i < curve->get_point_count(); i++) {
  			Vector2 prev_p = curve->get_point_position(i);
  
  			for (int j = 1; j <= 8; j++) {
  				real_t frac = j / 8.0;
  				Vector2 p = curve->interpolate(i, frac);
  				draw_line(prev_p, p, color, line_width, true);
  				prev_p = p;
  			}
  		}
  	}
  }
  
  void Path2D::_curve_changed() {
  	if (!is_inside_tree()) {
  		return;
  	}
  
  	if (!Engine::get_singleton()->is_editor_hint() && !get_tree()->is_debugging_navigation_hint()) {
  		return;
  	}
  
  	update();
  }
  
  void Path2D::set_curve(const Ref<Curve2D> &p_curve) {
  	if (curve.is_valid()) {
  		curve->disconnect("changed", this, "_curve_changed");
  	}
  
  	curve = p_curve;
  
  	if (curve.is_valid()) {
  		curve->connect("changed", this, "_curve_changed");
  	}
  
  	_curve_changed();
  }
  
  Ref<Curve2D> Path2D::get_curve() const {
  	return curve;
  }
  
  void Path2D::_bind_methods() {
  	ClassDB::bind_method(D_METHOD("set_curve", "curve"), &Path2D::set_curve);
  	ClassDB::bind_method(D_METHOD("get_curve"), &Path2D::get_curve);
  	ClassDB::bind_method(D_METHOD("_curve_changed"), &Path2D::_curve_changed);
  
  	ADD_PROPERTY(PropertyInfo(Variant::OBJECT, "curve", PROPERTY_HINT_RESOURCE_TYPE, "Curve2D"), "set_curve", "get_curve");
  }
  
  Path2D::Path2D() {
  	set_curve(Ref<Curve2D>(memnew(Curve2D))); //create one by default
  	set_self_modulate(Color(0.5, 0.6, 1.0, 0.7));
  }
  
  /////////////////////////////////////////////////////////////////////////////////
  
  void PathFollow2D::_update_transform() {
  	if (!path) {
  		return;
  	}
  
  	Ref<Curve2D> c = path->get_curve();
  	if (!c.is_valid()) {
  		return;
  	}
  
  	float path_length = c->get_baked_length();
  	if (path_length == 0) {
  		return;
  	}
  	Vector2 pos = c->interpolate_baked(offset, cubic);
  
  	if (rotate) {
  		float ahead = offset + lookahead;
  
  		if (loop && ahead >= path_length) {
  			// If our lookahead will loop, we need to check if the path is closed.
  			int point_count = c->get_point_count();
  			if (point_count > 0) {
  				Vector2 start_point = c->get_point_position(0);
  				Vector2 end_point = c->get_point_position(point_count - 1);
  				if (start_point == end_point) {
  					// Since the path is closed we want to 'smooth off'
  					// the corner at the start/end.
  					// So we wrap the lookahead back round.
  					ahead = Math::fmod(ahead, path_length);
  				}
  			}
  		}
  
  		Vector2 ahead_pos = c->interpolate_baked(ahead, cubic);
  
  		Vector2 tangent_to_curve;
  		if (ahead_pos == pos) {
  			// This will happen at the end of non-looping or non-closed paths.
  			// We'll try a look behind instead, in order to get a meaningful angle.
  			tangent_to_curve =
  					(pos - c->interpolate_baked(offset - lookahead, cubic)).normalized();
  		} else {
  			tangent_to_curve = (ahead_pos - pos).normalized();
  		}
  
  		Vector2 normal_of_curve = -tangent_to_curve.tangent();
  
  		pos += tangent_to_curve * h_offset;
  		pos += normal_of_curve * v_offset;
  
  		set_rotation(tangent_to_curve.angle());
  
  	} else {
  		pos.x += h_offset;
  		pos.y += v_offset;
  	}
  
  	set_position(pos);
  }
  
  void PathFollow2D::_notification(int p_what) {
  	switch (p_what) {
  		case NOTIFICATION_ENTER_TREE: {
  			path = Object::cast_to<Path2D>(get_parent());
  			if (path) {
  				_update_transform();
  			}
  
  		} break;
  		case NOTIFICATION_EXIT_TREE: {
  			path = nullptr;
  		} break;
  	}
  }
  
  void PathFollow2D::set_cubic_interpolation(bool p_enable) {
  	cubic = p_enable;
  }
  
  bool PathFollow2D::get_cubic_interpolation() const {
  	return cubic;
  }
  
  void PathFollow2D::_validate_property(PropertyInfo &property) const {
  	if (property.name == "offset") {
  		float max = 10000;
  		if (path && path->get_curve().is_valid()) {
  			max = path->get_curve()->get_baked_length();
  		}
  
  		property.hint_string = "0," + rtos(max) + ",0.01,or_lesser,or_greater";
  	}
  }
  
  String PathFollow2D::get_configuration_warning() const {
  	if (!is_visible_in_tree() || !is_inside_tree()) {
  		return String();
  	}
  
  	String warning = Node2D::get_configuration_warning();
  	if (!Object::cast_to<Path2D>(get_parent())) {
  		if (warning != String()) {
  			warning += "\n\n";
  		}
  		warning += TTR("PathFollow2D only works when set as a child of a Path2D node.");
  	}
  
  	return warning;
  }
  
  void PathFollow2D::_bind_methods() {
  	ClassDB::bind_method(D_METHOD("set_offset", "offset"), &PathFollow2D::set_offset);
  	ClassDB::bind_method(D_METHOD("get_offset"), &PathFollow2D::get_offset);
  
  	ClassDB::bind_method(D_METHOD("set_h_offset", "h_offset"), &PathFollow2D::set_h_offset);
  	ClassDB::bind_method(D_METHOD("get_h_offset"), &PathFollow2D::get_h_offset);
  
  	ClassDB::bind_method(D_METHOD("set_v_offset", "v_offset"), &PathFollow2D::set_v_offset);
  	ClassDB::bind_method(D_METHOD("get_v_offset"), &PathFollow2D::get_v_offset);
  
  	ClassDB::bind_method(D_METHOD("set_unit_offset", "unit_offset"), &PathFollow2D::set_unit_offset);
  	ClassDB::bind_method(D_METHOD("get_unit_offset"), &PathFollow2D::get_unit_offset);
  
  	ClassDB::bind_method(D_METHOD("set_rotate", "enable"), &PathFollow2D::set_rotate);
  	ClassDB::bind_method(D_METHOD("is_rotating"), &PathFollow2D::is_rotating);
  
  	ClassDB::bind_method(D_METHOD("set_cubic_interpolation", "enable"), &PathFollow2D::set_cubic_interpolation);
  	ClassDB::bind_method(D_METHOD("get_cubic_interpolation"), &PathFollow2D::get_cubic_interpolation);
  
  	ClassDB::bind_method(D_METHOD("set_loop", "loop"), &PathFollow2D::set_loop);
  	ClassDB::bind_method(D_METHOD("has_loop"), &PathFollow2D::has_loop);
  
  	ClassDB::bind_method(D_METHOD("set_lookahead", "lookahead"), &PathFollow2D::set_lookahead);
  	ClassDB::bind_method(D_METHOD("get_lookahead"), &PathFollow2D::get_lookahead);
  
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "offset", PROPERTY_HINT_RANGE, "0,10000,0.01,or_lesser,or_greater"), "set_offset", "get_offset");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "unit_offset", PROPERTY_HINT_RANGE, "0,1,0.0001,or_lesser,or_greater", PROPERTY_USAGE_EDITOR), "set_unit_offset", "get_unit_offset");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "h_offset"), "set_h_offset", "get_h_offset");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "v_offset"), "set_v_offset", "get_v_offset");
  	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "rotate"), "set_rotate", "is_rotating");
  	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "cubic_interp"), "set_cubic_interpolation", "get_cubic_interpolation");
  	ADD_PROPERTY(PropertyInfo(Variant::BOOL, "loop"), "set_loop", "has_loop");
  	ADD_PROPERTY(PropertyInfo(Variant::REAL, "lookahead", PROPERTY_HINT_RANGE, "0.001,1024.0,0.001"), "set_lookahead", "get_lookahead");
  }
  
  void PathFollow2D::set_offset(float p_offset) {
  	offset = p_offset;
  	if (path) {
  		if (path->get_curve().is_valid()) {
  			float path_length = path->get_curve()->get_baked_length();
  
  			if (loop) {
  				offset = Math::fposmod(offset, path_length);
  				if (!Math::is_zero_approx(p_offset) && Math::is_zero_approx(offset)) {
  					offset = path_length;
  				}
  			} else {
  				offset = CLAMP(offset, 0, path_length);
  			}
  		}
  
  		_update_transform();
  	}
  	_change_notify("offset");
  	_change_notify("unit_offset");
  }
  
  void PathFollow2D::set_h_offset(float p_h_offset) {
  	h_offset = p_h_offset;
  	if (path) {
  		_update_transform();
  	}
  }
  
  float PathFollow2D::get_h_offset() const {
  	return h_offset;
  }
  
  void PathFollow2D::set_v_offset(float p_v_offset) {
  	v_offset = p_v_offset;
  	if (path) {
  		_update_transform();
  	}
  }
  
  float PathFollow2D::get_v_offset() const {
  	return v_offset;
  }
  
  float PathFollow2D::get_offset() const {
  	return offset;
  }
  
  void PathFollow2D::set_unit_offset(float p_unit_offset) {
  	if (path && path->get_curve().is_valid() && path->get_curve()->get_baked_length()) {
  		set_offset(p_unit_offset * path->get_curve()->get_baked_length());
  	}
  }
  
  float PathFollow2D::get_unit_offset() const {
  	if (path && path->get_curve().is_valid() && path->get_curve()->get_baked_length()) {
  		return get_offset() / path->get_curve()->get_baked_length();
  	} else {
  		return 0;
  	}
  }
  
  void PathFollow2D::set_lookahead(float p_lookahead) {
  	lookahead = p_lookahead;
  }
  
  float PathFollow2D::get_lookahead() const {
  	return lookahead;
  }
  
  void PathFollow2D::set_rotate(bool p_rotate) {
  	rotate = p_rotate;
  	_update_transform();
  }
  
  bool PathFollow2D::is_rotating() const {
  	return rotate;
  }
  
  void PathFollow2D::set_loop(bool p_loop) {
  	loop = p_loop;
  }
  
  bool PathFollow2D::has_loop() const {
  	return loop;
  }
  
  PathFollow2D::PathFollow2D() {
  	offset = 0;
  	h_offset = 0;
  	v_offset = 0;
  	path = nullptr;
  	rotate = true;
  	cubic = true;
  	loop = true;
  	lookahead = 4;
  }
  