nplot-gtk/lib/ArrowItem.cs

/*
NPlot - A charting library for .NET

ArrowItem.cs
Copyright (C) 2003
Matt Howlett

Redistribution and use of NPlot or parts there-of in source and
binary forms, with or without modification, are permitted provided
that the following conditions are met:

1. Re-distributions in source form must retain at the head of each
   source file the above copyright notice, this list of conditions
   and the following disclaimer.

2. Any product ("the product") that makes use NPlot or parts 
   there-of must either:
  
    (a) allow any user of the product to obtain a complete machine-
        readable copy of the corresponding source code for the 
        product and the version of NPlot used for a charge no more
        than your cost of physically performing source distribution,
	    on a medium customarily used for software interchange, or:

    (b) reproduce the following text in the documentation, about 
        box or other materials intended to be read by human users
        of the product that is provided to every human user of the
        product: 
   
              "This product includes software developed as 
              part of the NPlot library project available 
              from: http://www.nplot.com/" 

        The words "This product" may optionally be replace with 
        the actual name of the product.

------------------------------------------------------------------------

THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

*/

using System;
using System.Drawing;

namespace NPlot
{

	/// <summary>
	/// An Arrow IDrawable, with a text label that is automatically
	/// nicely positioned at the non-pointy end of the arrow. Future
	/// feature idea: have constructor that takes a dataset, and have
	/// the arrow know how to automatically set it's angle to avoid 
	/// the data.
	/// </summary>
	public class ArrowItem : IDrawable
	{

		private void Init()
		{
			FontFamily fontFamily = new FontFamily("Arial");
			font_ = new Font(fontFamily, 10, FontStyle.Regular, GraphicsUnit.Pixel);
		}


		/// <summary>
		/// Default constructor : 
		/// text = ""
		/// angle = 45 degrees anticlockwise from horizontal.
		/// </summary>
		/// <param name="position">The position the arrow points to.</param>
		public ArrowItem( PointD position )
		{
			to_ = position;
			Init();
		}


		/// <summary>
		/// Constructor
		/// </summary>
		/// <param name="position">The position the arrow points to.</param>
		/// <param name="angle">angle of arrow with respect to x axis.</param>
		public ArrowItem( PointD position, double angle )
		{
			to_ = position;
			angle_ = -angle;
			Init();
		}


		/// <summary>
		/// Constructor
		/// </summary>
		/// <param name="position">The position the arrow points to.</param>
		/// <param name="angle">angle of arrow with respect to x axis.</param>
		/// <param name="text">The text associated with the arrow.</param>
		public ArrowItem( PointD position, double angle, string text )
		{
			to_ = position;
			angle_ = -angle;
			text_ = text;
			Init();
		}


		/// <summary>
		/// Text associated with the arrow.
		/// </summary>
		public string Text 
		{
			get
			{
				return text_;
			}
			set
			{
				text_ = value;
			}
		}
		private string text_ = "";


		/// <summary>
		/// Angle of arrow anti-clockwise to right horizontal in degrees.
		/// </summary>
		/// <remarks>The code relating to this property in the Draw method is
		/// a bit weird. Internally, all rotations are clockwise [this is by 
		/// accient, I wasn't concentrating when I was doing it and was half
		/// done before I realised]. The simplest way to make angle represent
		/// anti-clockwise rotation (as it is normal to do) is to make the 
		/// get and set methods negate the provided value.</remarks>
		public double Angle
		{
			get
			{
				return -angle_;
			}
			set
			{
				angle_ = -value;
			}
		}
		private double angle_ = -45.0;


		/// <summary>
		/// Physical length of the arrow. 
		/// </summary>
		public float PhysicalLength
		{
			get
			{
				return physicalLength_;
			}
			set
			{
				physicalLength_ = value;
			}
		}
		private float physicalLength_ = 40.0f;


		/// <summary>
		/// The point the arrow points to.
		/// </summary>
		public PointD To
		{
			get
			{
				return to_;
			}
			set
			{
				to_ = value;
			}
		}
		private PointD to_;


		/// <summary>
		/// Size of the arrow head sides in pixels.
		/// </summary>
		public float HeadSize
		{
			get
			{
				return headSize_;
			}
			set
			{
				headSize_ = value;
			}
		}
		private float headSize_ = 10.0f;


		/// <summary>
		/// angle between sides of arrow head in degrees
		/// </summary>
		public float HeadAngle
		{
			get
			{
				return headAngle_;
			}
			set
			{
				headAngle_ = value;
			}
		}
		private float headAngle_ = 40.0f;


		/// <summary>
		/// Draws the arrow on a plot surface.
		/// </summary>
		/// <param name="g">graphics surface on which to draw</param>
		/// <param name="xAxis">The X-Axis to draw against.</param>
		/// <param name="yAxis">The Y-Axis to draw against.</param>
		public void Draw( System.Drawing.Graphics g, PhysicalAxis xAxis, PhysicalAxis yAxis )
		{
            if (this.To.X > xAxis.Axis.WorldMax || this.To.X < xAxis.Axis.WorldMin)
                return;

            if (this.To.Y > yAxis.Axis.WorldMax || this.To.Y < yAxis.Axis.WorldMin)
                return;

            double angle = this.angle_;

			if (this.angle_ < 0.0)
			{
				int mul = -(int)(this.angle_ / 360.0) + 2;
				angle = angle_ + 360.0 * (double)mul;
			}

			double normAngle = (double)angle % 360.0;   // angle in range 0 -> 360.

			Point toPoint = new Point( 
				(int)xAxis.WorldToPhysical( to_.X, true ).X,
				(int)yAxis.WorldToPhysical( to_.Y, true ).Y );


			float xDir = (float)Math.Cos( normAngle * 2.0 * Math.PI / 360.0 );
			float yDir = (float)Math.Sin( normAngle * 2.0 * Math.PI / 360.0 );

			toPoint.X += (int)(xDir*headOffset_);
			toPoint.Y += (int)(yDir*headOffset_);

			float xOff = physicalLength_ * xDir;
			float yOff = physicalLength_ * yDir;

			Point fromPoint = new Point(
				(int)(toPoint.X + xOff),
				(int)(toPoint.Y + yOff) );

			g.DrawLine( pen_, toPoint, fromPoint );

			Point[] head = new Point[3];

			head[0] = toPoint;

			xOff = headSize_ * (float)Math.Cos( (normAngle-headAngle_/2.0f) * 2.0 * Math.PI / 360.0 );
			yOff = headSize_ * (float)Math.Sin( (normAngle-headAngle_/2.0f) * 2.0 * Math.PI / 360.0 );

			head[1] = new Point(
				(int)(toPoint.X + xOff),
				(int)(toPoint.Y + yOff) );

			float xOff2 = headSize_ * (float)Math.Cos( (normAngle+headAngle_/2.0f) * 2.0 * Math.PI / 360.0 );
			float yOff2 = headSize_ * (float)Math.Sin( (normAngle+headAngle_/2.0f) * 2.0 * Math.PI / 360.0 );

			head[2] = new Point(
				(int)(toPoint.X + xOff2),
				(int)(toPoint.Y + yOff2) );

			g.FillPolygon( arrowBrush_, head );

			SizeF textSize = g.MeasureString( text_, font_ );
			SizeF halfSize = new SizeF( textSize.Width / 2.0f, textSize.Height / 2.0f );

			float quadrantSlideLength = halfSize.Width + halfSize.Height;

			float quadrantF = (float)normAngle / 90.0f;       // integer part gives quadrant.
			int quadrant = (int)quadrantF;	          // quadrant in. 
			float prop = quadrantF - (float)quadrant; // proportion of way through this qadrant. 
			float dist = prop * quadrantSlideLength;	  // distance along quarter of bounds rectangle.
			
			// now find the offset from the middle of the text box that the
			// rear end of the arrow should end at (reverse this to get position
			// of text box with respect to rear end of arrow).
			//
			// There is almost certainly an elgant way of doing this involving
			// trig functions to get all the signs right, but I'm about ready to 
			// drop off to sleep at the moment, so this blatent method will have 
			// to do.
			PointF offsetFromMiddle = new PointF( 0.0f, 0.0f );
			switch (quadrant)
			{
				case 0:
					if (dist > halfSize.Height)
					{
						dist -= halfSize.Height;
						offsetFromMiddle = new PointF( -halfSize.Width + dist, halfSize.Height );
					}
					else
					{
						offsetFromMiddle = new PointF( -halfSize.Width, - dist );
					}
					break;

				case 1:
					if (dist > halfSize.Width)
					{
						dist -= halfSize.Width;
						offsetFromMiddle = new PointF( halfSize.Width, halfSize.Height - dist );
					}
					else
					{
						offsetFromMiddle = new PointF( dist, halfSize.Height );
					}
					break;

				case 2:
					if (dist > halfSize.Height)
					{
						dist -= halfSize.Height;
						offsetFromMiddle = new PointF( halfSize.Width - dist, -halfSize.Height );
					}
					else
					{
						offsetFromMiddle = new PointF( halfSize.Width, -dist );
					}

					break;

				case 3:
					if (dist > halfSize.Width)
					{
						dist -= halfSize.Width;
						offsetFromMiddle = new PointF( -halfSize.Width, -halfSize.Height + dist );
					}
					else
					{
						offsetFromMiddle = new PointF( -dist, -halfSize.Height );
					}

					break;

				default:
					throw new NPlotException( "Programmer error." );

			}

			g.DrawString( 
				text_, font_, textBrush_,
				(int)(fromPoint.X - halfSize.Width - offsetFromMiddle.X),
				(int)(fromPoint.Y - halfSize.Height + offsetFromMiddle.Y) );

		}


		/// <summary>
		/// The brush used to draw the text associated with the arrow.
		/// </summary>
		public Brush TextBrush
		{
			get
			{
				return textBrush_;
			}
			set
			{
				textBrush_ = value;
			}
		}

	
		/// <summary>
		/// Set the text to be drawn with a solid brush of this color.
		/// </summary>
		public Color TextColor
		{
			set
			{
				textBrush_ = new SolidBrush( value );
			}
		}


		/// <summary>
		/// The color of the pen used to draw the arrow.
		/// </summary>
		public Color ArrowColor
		{
			get
			{
				return pen_.Color;
			}
			set
			{
				pen_.Color = value;
				arrowBrush_ = new SolidBrush( value );
			}
		}
			
		
		/// <summary>
		/// The font used to draw the text associated with the arrow.
		/// </summary>
		public Font TextFont
		{
			get
			{
				return this.font_;
			}
			set
			{
				this.font_ = value;
			}
		}


		/// <summary>
		/// Offset the whole arrow back in the arrow direction this many pixels from the point it's pointing to.
		/// </summary>
		public int HeadOffset
		{
			get
			{
				return headOffset_;
			}
			set
			{
				headOffset_ = value;
			}
		}
		private int headOffset_ = 2;


		private Brush arrowBrush_ = new SolidBrush( Color.Black );
		private Brush textBrush_ = new SolidBrush( Color.Black );
		private Pen pen_ = new Pen( Color.Black );
		private Font font_;
	}
}