Grid.java

/*******************************************************************************
 * Copyright (c) 2008-2009 SWTChart project. All rights reserved. 
 * 
 * This code is distributed under the terms of the Eclipse Public License v1.0
 * which is available at http://www.eclipse.org/legal/epl-v10.html
 *******************************************************************************/
package org.swtchart.internal;

import java.util.ArrayList;

import org.eclipse.swt.SWT;
import org.eclipse.swt.graphics.Color;
import org.eclipse.swt.graphics.GC;
import org.eclipse.swt.widgets.Display;
import org.swtchart.IGrid;
import org.swtchart.LineStyle;
import org.swtchart.internal.axis.Axis;

/**
 * A grid.
 */
public class Grid implements IGrid
{

    /** the axis */
    private Axis axis;

    /** the grid color */
    private Color color;

    /** the visibility state */
    private boolean isVisible;

    /** the line style */
    private LineStyle lineStyle;

    /** the line width */
    private final static int LINE_WIDTH = 1;

    /** the default style */
    private final static LineStyle DEFAULT_STYLE = LineStyle.DOT;

    /** the default color */
    private final static int DEFAULT_FOREGROUND = SWT.COLOR_GRAY;

    /**
     * Constructor.
     * 
     * @param axis
     *            the axis
     */
    public Grid ( Axis axis )
    {
        this.axis = axis;

        color = Display.getDefault ().getSystemColor ( DEFAULT_FOREGROUND );
        lineStyle = DEFAULT_STYLE;
        isVisible = true;
    }

    /*
     * @see IGrid#getForeground()
     */
    public Color getForeground ()
    {
        if ( color.isDisposed () )
        {
            color = Display.getDefault ().getSystemColor ( DEFAULT_FOREGROUND );
        }
        return color;
    }

    /*
     * @see IGrid#setForeground(Color)
     */
    public void setForeground ( Color color )
    {
        if ( color != null && color.isDisposed () )
        {
            SWT.error ( SWT.ERROR_INVALID_ARGUMENT );
        }

        if ( color == null )
        {
            this.color = Display.getDefault ().getSystemColor ( DEFAULT_FOREGROUND );
        }
        else
        {
            this.color = color;
        }
    }

    /*
     * @see IGrid#getStyle()
     */
    public LineStyle getStyle ()
    {
        return lineStyle;
    }

    /*
     * @see IGrid#setStyle(LineStyle)
     */
    public void setStyle ( LineStyle style )
    {
        if ( style == null )
        {
            this.lineStyle = DEFAULT_STYLE;
        }
        else
        {
            this.lineStyle = style;
        }
    }

    /**
     * Draws grid.
     * 
     * @param gc
     *            the graphics context
     * @param width
     *            the width to draw grid
     * @param height
     *            the height to draw grid
     */
    protected void draw ( GC gc, int width, int height )
    {
        if ( !isVisible || lineStyle.equals ( LineStyle.NONE ) )
        {
            return;
        }

        int xWidth;
        if ( axis.isHorizontalAxis () )
        {
            xWidth = width;
        }
        else
        {
            xWidth = height;
        }

        gc.setForeground ( getForeground () );
        ArrayList<Integer> tickLabelPosition = axis.getTick ().getAxisTickLabels ().getTickLabelPositions ();

        gc.setLineStyle ( Util.getIndexDefinedInSWT ( lineStyle ) );
        if ( axis.isValidCategoryAxis () )
        {
            int step = 0;
            if ( tickLabelPosition.size () > 1 )
            {
                step = tickLabelPosition.get ( 1 ).intValue () - tickLabelPosition.get ( 0 ).intValue ();
            }
            else
            {
                step = xWidth;
            }
            int x = (int) ( tickLabelPosition.get ( 0 ).intValue () - step / 2d );

            for ( int i = 0; i < tickLabelPosition.size () + 1; i++ )
            {
                x += step;
                if ( x >= xWidth )
                {
                    continue;
                }

                if ( axis.isHorizontalAxis () )
                {
                    gc.drawLine ( x, LINE_WIDTH, x, height - LINE_WIDTH );
                }
                else
                {
                    gc.drawLine ( LINE_WIDTH, x, width - LINE_WIDTH, x );
                }
            }
        }
        else
        {
            for ( int i = 0; i < tickLabelPosition.size (); i++ )
            {
                int x = tickLabelPosition.get ( i ).intValue ();
                if ( x >= xWidth )
                {
                    continue;
                }

                if ( axis.isHorizontalAxis () )
                {
                    gc.drawLine ( x, LINE_WIDTH, x, height - LINE_WIDTH );
                }
                else
                {
                    gc.drawLine ( LINE_WIDTH, height - 1 - x, width - LINE_WIDTH, height - 1 - x );
                }
            }
        }
    }
}