2D : Simple mouse drawing demo

2d/simple_mouse_drawing/MouseDrawing.gd

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+extends Node2D
+
+const line_width = 10
+
+var pos_track = 0
+var pos0 = Vector2()
+var pos1 = Vector2()
+
+func _input(event):
+	if (event.type == InputEvent.MOUSE_BUTTON):
+		if (event.pressed):
+
+			var mpos = get_viewport().get_mouse_pos()
+			if (pos_track == 0):
+				pos0 = mpos
+			else:
+				# on second click, create the "line"
+				pos1 = mpos
+				gen_poly_line()
+			# XOR flips 1 to 0 and 0 to 1, for switching states
+			pos_track ^= 1
+
+
+func gen_poly_line():
+	# create a new Polygon2D node.
+	var node = Polygon2D.new()
+
+	# do maths to produce a line shape (rectangle) 
+	node.set_polygon(create_poly_coords_for_line(pos0, pos1, line_width))
+
+	# attach the node to this object, and therfore include it in the scene
+	add_child(node)
+
+	# basic way to keep track of the added lines
+	node.add_to_group("DrawLines")
+
+
+func create_poly_coords_for_line(start, end, width):
+	# Creates 2 points each for start and end point of a line;
+	# these points make up the corners of the rectangle that is the line representation.
+
+	width = width / 2
+
+	# Take the difference between start and end, make it a unit vector (normalized),
+	# make it perpendicular (tangent), make it half the line width long (* width) , finally
+	# offset it by adding it to start or end.
+	var s1 = start + ((start - end).normalized().tangent()  * width)
+	var s2 = start + ((start - end).normalized().tangent()  * -width)
+	var e1 = end + ((end - start).normalized().tangent() * width)
+	var e2 = end + ((end - start).normalized().tangent() * -width)
+
+	# This array of 2D points will make up the path of the polygon
+	return Vector2Array([s1, s2, e1, e2])
+
+
+func _ready():
+	set_process_input(true)

2d/simple_mouse_drawing/MouseDrawing.tscn

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+[gd_scene load_steps=3 format=1]
+
+[ext_resource path="res://MouseDrawing.gd" type="Script" id=1]
+
+[sub_resource type="GDScript" id=1]
+
+script/source = "extends Control
+
+# this function is connected to a signal on the button node
+func _on_Button_pressed():
+	for poly in get_tree().get_nodes_in_group(\"DrawLines\"):
+		poly.queue_free()
+
+"
+
+[node name="Node2D" type="Node2D"]
+
+script/script = ExtResource( 1 )
+
+[node name="GUI" type="Control" parent="."]
+
+focus/ignore_mouse = false
+focus/stop_mouse = true
+size_flags/horizontal = 2
+size_flags/vertical = 2
+margin/left = 0.0
+margin/top = 0.0
+margin/right = 292.0
+margin/bottom = 67.0
+script/script = SubResource( 1 )
+
+[node name="Label" type="Label" parent="GUI"]
+
+focus/ignore_mouse = true
+focus/stop_mouse = true
+size_flags/horizontal = 2
+size_flags/vertical = 0
+margin/left = 0.0
+margin/top = 0.0
+margin/right = 276.0
+margin/bottom = 24.0
+text = "Click 2 places to create line between them."
+percent_visible = 1.0
+lines_skipped = 0
+max_lines_visible = -1
+
+[node name="Button" type="Button" parent="GUI"]
+
+focus/ignore_mouse = false
+focus/stop_mouse = true
+size_flags/horizontal = 2
+size_flags/vertical = 2
+margin/left = 7.0
+margin/top = 25.0
+margin/right = 99.0
+margin/bottom = 55.0
+toggle_mode = false
+enabled_focus_mode = 2
+shortcut = null
+text = "Clear"
+flat = false
+
+[connection signal="pressed" from="GUI/Button" to="GUI" method="_on_Button_pressed"]
+
+

2d/simple_mouse_drawing/README.md

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+### Simple Mouse Drawing Demo
+
+Click 2 points to create a line between them.
+
+Demonstrates:
+
+	* Procedural 2DPolygon generation and Node instancing.
+
+	* Mouse input handling.

2d/simple_mouse_drawing/engine.cfg

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+[application]
+
+name="SimpleMouseDrawing"
+main_scene="res://MouseDrawing.tscn"
+icon="res://icon.png"
+
+[display]
+
+width=1024
+height=768
+resizable=true
+stretch_aspect="keep"
+
+[physics_2d]
+
+cell_size=64