带滑块的趋势图(slider control in chart)

      如果没记错的话，好像是第一次在用趋势图显示数据的时候，就遇到过这个问题，当时是在一个趋势图中显示一个月中每天的数据趋势变化，结果就是根本在一张图中显示不下，X轴的文字标注都重叠到一起，当时用的是PB，里面的图形显示功能非常强大，后来好像是将文字直立显示的，避免了标注的重叠。

      最近同时好像在搞趋势图，又想起这个问题，就试着在里面加个slider实现拖动以便可以显示“被多出”的部分。老规矩，先看图。

      

      嘿嘿，其实也没用到什么，纯GDI+，用到的也不外乎就是双缓存和坐标变换。主要处理的事件就是MouseDown和MouseMove，重绘Paint。在MouseDown中变化X轴的值和Value值（这里也有变换坐标），在MouseMove中变换坐标，Paint中绘制轴、趋势图、滑块。

      下面看看完整的代码：

        /// <summary>
        /// X轴和Value值重加载
        /// </summary>
        private void lbchart_MouseDown(object sender, MouseEventArgs e)
        {
            //是否点中滑块
            IsClick = IsClickSlider(new Point(e.X, e.Y));
            //左键有效
            if (e.Button == MouseButtons.Left)
            {
                double disvalue = 0; //位移
                if (curPoint.X != e.X || curPoint.Y != e.Y)
                {
                    curPoint.X = e.X;
                    curPoint.Y = e.Y;
                    Capture = true;
                    //是否需要移动
                    if (IsClick)
                    {
                        IsNeedMove = true;
                    }
                    //位移差
                    disvalue =curPoint.X - oldPoint.X;
                }
                else
                {
                    IsNeedMove = false;
                    //位移差
                    disvalue = dx;
                }

                //重新复制PartValue中的值
                //****x轴移动的位移
                int xd = (int)Math.Round(disvalue / xdvalue);
                curArrPos = curArrPos + xd;
                if (curArrPos < 0)
                {
                    curArrPos = 0;
                }
                if (curArrPos > 6)
                {
                    curArrPos = 6;
                }
                for (int i = curArrPos; i < curArrPos + 7; i++)
                {
                    xPartValue[i - curArrPos] = xValue[i];
                    partValue[i - curArrPos] = value[i];
                }
            }
            if (e.Button == MouseButtons.Right)
            {
                Capture = false;
            }
            dx = 0;
            this.lbchart.Invalidate();
        }


        /// <summary>
        /// 鼠标移动
        /// </summary>
        private void lbchart_MouseMove(object sender, MouseEventArgs e)
        {
            Graphics g2 = CreateGraphics();
            if (IsNeedMove)
            {
                dx = dx + (e.X - oldPoint.X);
                curPoint = new Point(e.X, e.Y);
            }
            this.lbchart.Invalidate();
        }

       上面是两个主要的鼠标事件,下面看看绘制代码：

       #region 重绘
       private void lbchart_Paint(object sender, PaintEventArgs e)
       {
            //初始化值
            g0 = e.Graphics;
            bitmap = new Bitmap(lbchart.Width, lbchart.Height);
            g1 = Graphics.FromImage(bitmap);
            g1.Clear(this.lbchart.BackColor);
            g1.SmoothingMode = SmoothingMode.AntiAlias;

            #region 绘制
            //轴
            DrawAxes();
            //趋势图
            DrawChart();
            //滑块
            DrawSlider();
            #endregion

            //绘制到lb上
            g0.DrawImage(bitmap, 0, 0);

        }

        /// <summary>
        /// 绘制轴
        /// </summary>
        private void DrawAxes()
        {
            Brush axesbrush = new SolidBrush(Color.Black);
            Font axesfont = new Font("宋体", 15, FontStyle.Bold);
            Font valuefont = new Font("宋体", 10, FontStyle.Regular);

            //箭头
            AdjustableArrowCap cap = new AdjustableArrowCap(3, 3);
            cap.WidthScale = 3;
            cap.BaseCap = LineCap.Square;
            cap.Height = 3;
            axesPen.CustomStartCap = cap;

            //****Y轴
            g1.DrawLine(axesPen, lbPosX + 10, lbPosY + 10, lbPosX + 10, lbHeight - 30);
            g1.DrawString("Y", axesfont, axesbrush, lbPosX + 15, lbPosY + 10);
            //*****Y轴差值
            ydvalue = ((lbHeight - 15) - (lbPosY + 10)) / (yValue.Length + 1);
            for (int i = 0; i < yValue.Length; i++)
            {
                float y = (float)(lbHeight - 15 - (i + 1) * ydvalue);
                g1.DrawString(yValue[i].ToString(), valuefont, axesbrush, lbPosX + 12, y);
                g1.DrawLine(valuePen, lbPosX + 10, y, lbPosX + 15, y);
            }

            //****X轴
            g1.DrawLine(axesPen, lbWidth - 5, lbHeight - 30, lbPosX + 10, lbHeight - 30);
            g1.DrawString("X", axesfont, axesbrush, lbWidth - 15, lbHeight - 55);
            //******X轴差值
            xdvalue = (lbWidth - 5 - (lbPosX + 10)) / (partValue.Length - 1);
            for (int i = 0; i < xPartValue.Length; i++)
            {
                float x = (float)(lbPosX + 10 + (i) * xdvalue);
                if (Convert.ToDouble(xPartValue[i].ToString()) >= 10)
                {
                    g1.DrawString(xPartValue[i].ToString(), valuefont, axesbrush, x - 12, lbHeight - 28);
                }
                else
                {
                    g1.DrawString(xPartValue[i].ToString(), valuefont, axesbrush, x - 5, lbHeight - 28);
                }
                g1.DrawLine(valuePen, x, lbHeight - 30, x, lbHeight - 35);
            }
        }

        /// <summary>
        /// 绘制趋势图
        /// </summary>
        private void DrawChart()
        {
            //****绘制曲线图
            double dvalue = ydvalue / 5.0;
            for (int i = 0; i < partValue.Length - 1; i++)
            {
                double startX = lbPosX + 10 + (i) * xdvalue;
                double endX = startX + xdvalue;
                double startY = Convert.ToDouble(partValue[i].ToString()) * dvalue;
                double endY = Convert.ToDouble(partValue[i + 1].ToString()) * dvalue;
                g1.DrawEllipse(new Pen(Color.Red), (float)(startX - 3), (float)(startY - 3), 6, 6);
                g1.DrawLine(valuePen, (float)endX, (float)endY, (float)startX, (float)startY);
            }
        }

        /// <summary>
        /// 绘制滑块
        /// </summary>
        private void DrawSlider()
        {
            //绘制滑块
            if (curPoint.X != 0 && curPoint.Y != 0)
            {
                oldPoint = curPoint;
                g1.DrawLine(sliderPen, lbPosX + curPoint.X, lbPosY, lbPosX + curPoint.X, lbPosY + lbHeight);
            }
            else
            {
                g1.DrawLine(sliderPen, lbWidth / 2, lbPosY, lbWidth / 2, lbPosY + lbHeight);
            }
        }

        #endregion