GridSample.cs

using System;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Input;
using Shapes2D.Drawing;
using Shapes2D.Samples.Shared;

namespace Shapes2D.Samples.Grid
{
	public enum GridType
	{
		Triangle = 3,
		Square = 4,
		Hexagon = 6
	}

	public class GridSample : SampleGame
	{
		// Change these variables to modify the generated grid.
		private static readonly GridType GridType = GridType.Hexagon;
		private static readonly Vector2 Scale = new Vector2(50);
		private static readonly Color BaseColor = Color.SaddleBrown;

		private readonly PrimitiveBatch primitiveBatch;
		private float paintDistanceSquared;

		public GridSample()
		{
			// Create a new PrimitiveBatch, which can be used to draw 2D lines and shapes.
			primitiveBatch = new PrimitiveBatch(this);
			Components.Add(primitiveBatch);

			paintDistanceSquared = Scale.LengthSquared();
		}

		protected override void Initialize()
		{
			base.Initialize();

			var ratio = GridType == GridType.Square ? Vector2.One : new Vector2(TriangleRatio, 1);

			var p = GridType == GridType.Triangle ? 2 :
					GridType == GridType.Hexagon ? 4f / 3 : 1;

			var height = Graphics.PreferredBackBufferHeight / Scale.Y * p + 1;
			var width = Graphics.PreferredBackBufferWidth / (int)(ratio.X * Scale.X);

			for (var y = 0; y <= height; y++)
			{
				var position = new Vector2(0, y * Scale.Y / p);

				switch (GridType)
				{
					case GridType.Triangle:
						position.X += Scale.X * ratio.X * 2 / 3;
						if (y % 2 == 1) position.X += -Scale.X * ratio.X / 3;
						break;

					case GridType.Square:
						position += Scale / 2;
						break;

					case GridType.Hexagon:
						position.Y += -Scale.Y / 4;
						if (y % 2 == 1) position.X += Scale.X * ratio.X / 2;
						break;

					default:
						throw new ArgumentOutOfRangeException();
				}

				for (var x = 0; x <= width + 1; x++)
				{
					var even = x % 2 == y % 2;
					primitiveBatch.Primitives.Add(new RegularPolygon((int)GridType)
					{
						Position = position,
						Stretch = Scale,
						Rotation = GridType != GridType.Square ? (float)(Math.PI * (even ? -1 : +1) / 2f) : 0,
						Fill = GetRandomGridColor()
					});
					position.X += Scale.X * ratio.X * (GridType == GridType.Triangle ? (even ? 1 : 2) * 2f / 3 : 1);
				}
			}
		}

		protected override void Update(GameTime gameTime)
		{
			base.Update(gameTime);

			var scrollWheelOffset = CurrentMouseState.ScrollWheelValue - PreviousMouseState.ScrollWheelValue;
			paintDistanceSquared += scrollWheelOffset / 2f;
			if (paintDistanceSquared < 0) paintDistanceSquared = 0;

			var toggleButtonPressed = CurrentMouseState.MiddleButton == ButtonState.Pressed && PreviousMouseState.MiddleButton != ButtonState.Pressed;

			if (scrollWheelOffset != 0 || toggleButtonPressed || PreviousMouseState.Position != CurrentMouseState.Position || CurrentMouseState.LeftButton == ButtonState.Pressed || CurrentMouseState.RightButton == ButtonState.Pressed)
			{
				var mousePosition = CurrentMouseState.Position.ToVector2();
				bool? visible = null;

				for (var i = 0; i < primitiveBatch.Primitives.Count; i++)
				{
					var primitive = primitiveBatch.Primitives[i];
					var shape = primitive as Shape;

					if (toggleButtonPressed && shape != null)
					{
						if (visible == null) visible = shape.Fill == Color.Transparent;
						shape.Fill = visible.Value ? GetRandomGridColor() : Color.Transparent;
					}

					if (Vector2.DistanceSquared(primitive.Position, mousePosition) < paintDistanceSquared)
					{
						if (shape != null)
						{
							if (CurrentMouseState.LeftButton == ButtonState.Pressed) shape.Fill = GetRandomGridColor();
							else if (CurrentMouseState.RightButton == ButtonState.Pressed) shape.Fill = Color.Transparent;
						}

						primitive.Stroke = Color.Red;
					}
					else
					{
						primitive.Stroke = Color.Transparent;
					}
				}
			}
		}

		/// <summary>
		/// Returns a random color for each primitive in the grid.
		/// </summary>
		private static Color GetRandomGridColor()
		{
			return BaseColor.Darken(0, 0.75f).Lighten(0, 0.25f);
		}
	}
}