import org.eclipse.swt.events.PaintEvent;
import org.eclipse.swt.events.PaintListener;
import org.eclipse.swt.graphics.Image;
import org.eclipse.swt.graphics.ImageData;
import org.eclipse.swt.widgets.Composite;

/**
 * 可设置背景图片的Composite
 * Composite本身是可以设置背景图片的，但是只提供了平铺的显示方式，该类实现了居中、平铺和拉伸三种显示方式。
 * 
 * @author 003
 */
public class ImageComposite extends Composite
{
    /**
     * 居中
     */
    public static final String CENTRE = "Centre";
    
    /**
     * 平铺
     */
    public static final String TILED = "Tiled";

    /**
     * 拉伸
     */
    public static final String SCALED = "Scaled";

    /**
     * 背景图片
     */
    private Image backgroundImage;
    
    /**
     * 背景图片显示模式
     */
    private String imageDisplayMode;

    /**
     * 背景图片显示模式索引（引入此属性有助于必要时扩展）
     */
    private int modeIndex;

    /**
     * 构造一个没有背景图片的ImageComposite
     * @param parent 父组件
     * @param style 风格
     */
    public ImageComposite(Composite parent, int style)
    {
        this(parent, style, null, CENTRE);
    }
    
    /**
     * 构造一个具有指定背景图片和指定显示模式的ImageComposite
     * @param parent 父组件
     * @param style 风格
     * @param image 背景图片
     * @param modeName 背景图片显示模式
     */
    public ImageComposite(Composite parent, int style, Image image, String modeName)
    {
        super(parent, style);
        addPaintListener(new PaintListener()
        {
            @Override
            public void paintControl(PaintEvent e)
            {
                drawImage(e);
            }
        });
        setBackgroundImage(image);
        setImageDisplayMode(modeName);
    }

    /**
     * 获取背景图片
     * @return 背景图片
     * @see org.eclipse.swt.widgets.Control#getBackgroundImage(Image)
     */
    @Override
    public Image getBackgroundImage()
    {
        return backgroundImage;
    }

    /**
     * 设置背景图片
     * @param 背景图片
     * @see org.eclipse.swt.widgets.Control#setBackgroundImage(Image)
     */
    @Override
    public void setBackgroundImage(Image backgroundImage)
    {
        this.backgroundImage = backgroundImage;
        this.redraw();
    }

    /**
     * 获取背景图片显示模式
     * @return 显示模式
     */
    public String getImageDisplayMode()
    {
        return imageDisplayMode;
    }

    /**
     * 设置背景图片显示模式
     * @param modeName 模式名称，取值仅限于ImagePane.TILED  ImagePane.SCALED  ImagePane.CENTRE
     */
    public void setImageDisplayMode(String modeName)
    {
        if(modeName != null)
        {
            modeName = modeName.trim();
            
            //居中
            if(modeName.equalsIgnoreCase(CENTRE))
            {
                this.imageDisplayMode = CENTRE;
                modeIndex = 0;
            }
            //平铺
            else if(modeName.equalsIgnoreCase(TILED))
            {
                this.imageDisplayMode = TILED;
                modeIndex = 1;
            }
            //拉伸
            else if(modeName.equalsIgnoreCase(SCALED))
            {
                this.imageDisplayMode = SCALED;
                modeIndex = 2;
            }
            
            this.redraw();
        }
    }
    
    /**
     * 绘制背景
     * @param e PaintEvent
     */
    private void drawImage(PaintEvent e)
    {
        //如果设置了背景图片则显示
        if(backgroundImage != null)
        {
            int width = this.getSize().x;
            int height = this.getSize().y;
            int imageWidth = backgroundImage.getImageData().width;
            int imageHeight = backgroundImage.getImageData().height;
            
            switch(modeIndex)
            {
                //居中
                case 0:
                {
                    int x = (width - imageWidth) / 2;
                    int y = (height - imageHeight) / 2;
                    e.gc.drawImage(backgroundImage, x, y);
                    break;
                }
                //平铺
                case 1:
                {
                    for(int ix = 0; ix < width; ix += imageWidth)
                    {
                        for(int iy = 0; iy < height; iy += imageHeight)
                        {
                            e.gc.drawImage(backgroundImage, ix, iy);
                        }
                    }
                    
                    break;
                }
                //拉伸
                case 2:
                {
                    ImageData data = backgroundImage.getImageData().scaledTo(width, height);
                    e.gc.drawImage(new Image(e.display, data), 0, 0);
                    break;
                }
            }
        }
    }
}