HitTest的替代方案（）

Question

目前我的軟件在MSCharts中使用圖表對象的HitTest()方法，但是隨着我擴展到我的圖表上越來越多的數據點以及其他因素，這可能會導致巨大的性能下降。

我想知道是否有任何替代方案，你知道提供相同的功能（獲得X座標在圖表上的光標位置），但沒有性能打擊，因爲命中測試似乎是一種非常蠻力的方式獲得我的答案。

我的圖表從類System.Windows.Forms.DataVisualization.Charting.Chart

編輯爲清楚起見發佈：我要找到我的圖上的線的位置，以將其用於其他計算。

Answer 1

與mousewheel事件具有相同的性能問題。

這裏是我的解決方案：

1. 要獲取當前鼠標位置的座標軸值：

   double posX = Math.Round(currentArea.AxisX.PixelPositionToValue(e.X)); 
   double posY = Math.Round(currentArea.AxisY.PixelPositionToValue(e.Y)); 
   

   從Showing Mouse Axis Coordinates on Chart Control採取一點點的變化，以獲得更準確。

   但你應該檢查之前，鼠標處於ChartArea，否則它會拋出你一個異常。

2. 要獲得ChatElement上鼠標點：

   // Gets the ChartArea that the mouse points 
   private ChartArea mouseinChartArea(Chart source, Point e) 
   { 
       double relativeX = (double)e.X * 100/source.Width; 
       double relativeY = (double)e.Y * 100/source.Height; 
   
       foreach (ChartArea ca in source.ChartAreas) 
       { 
        if (relativeX > ca.Position.X && relativeX < ca.Position.Right && 
         relativeY > ca.Position.Y && relativeY < ca.Position.Bottom) 
         return ca; 
       } 
       return null; 
   } 
   
   // for my purpose, returns an axis. But you can return anything 
   private Axis findAxisforZooming(Chart source, Point e) 
   { 
       ChartArea currentArea = mouseinChartArea(source, new Point(e.X, e.Y)); // Check if inside 
       if (currentArea == null) 
        return null; 
   
       double axisXfontSize = currentArea.AxisX.LabelAutoFitMinFontSize + ((double)source.Width/SystemInformation.PrimaryMonitorSize.Width) 
        * (currentArea.AxisX.LabelAutoFitMaxFontSize - currentArea.AxisX.LabelAutoFitMinFontSize); 
       double axisYfontSize = currentArea.AxisY.LabelAutoFitMinFontSize + ((double)source.Height/SystemInformation.PrimaryMonitorSize.Height) 
        * (currentArea.AxisY.LabelAutoFitMaxFontSize - currentArea.AxisY.LabelAutoFitMinFontSize); 
       double axisYfontHeightSize = (axisYfontSize - currentArea.AxisY.LabelStyle.Font.Size) + currentArea.AxisY.LabelStyle.Font.Height; 
   
       Graphics g = this.CreateGraphics(); 
       if (currentArea.AxisX.LabelStyle.Font.Unit == GraphicsUnit.Point) 
        axisXfontSize = axisXfontSize * g.DpiX/72; 
       if (currentArea.AxisY.LabelStyle.Font.Unit == GraphicsUnit.Point) 
        axisYfontHeightSize = axisYfontHeightSize * g.DpiX/72; 
       g.Dispose(); 
   
       // Replacing the SystemInformation.PrimaryMonitorSize with the source.Width/Height will give the accurate TickMarks size. 
       // But it doens't count for the gab between the tickMarks and the axis lables (so by replacing, it give a good proximity with the gab) 
       int axisYTickMarks = (int)Math.Round(currentArea.AxisY.MajorTickMark.Size/100 * SystemInformation.PrimaryMonitorSize.Width); // source.Width; 
       int axisXTickMarks = (int)Math.Round(currentArea.AxisX.MajorTickMark.Size/100 * SystemInformation.PrimaryMonitorSize.Height); // source.Height; 
   
       int leftInnerPlot = (int)Math.Round(currentArea.Position.X/100 * source.Width + 
        currentArea.InnerPlotPosition.X/100 * currentArea.Position.Width/100 * source.Width); 
       int rightInnerPlot = (int)Math.Round(currentArea.Position.X/100 * this.chart1.Width + 
        currentArea.InnerPlotPosition.Right/100 * currentArea.Position.Width/100 * source.Width); 
       int topInnerPlot = (int)Math.Round(currentArea.Position.Y/100 * this.chart1.Height + 
        currentArea.InnerPlotPosition.Y/100 * currentArea.Position.Height/100 * source.Height); 
       int bottomInnerPlot = (int)Math.Round(currentArea.Position.Y/100 * source.Height + 
        currentArea.InnerPlotPosition.Bottom/100 * currentArea.Position.Height/100 * source.Height); 
   
       // Now you got the boundaries of every important ChartElement. 
       // Only left to check if the mouse is within your desire ChartElement, 
       // like the following:  
   
       bottomInnerPlot += axisXTickMarks + (int)Math.Round(axisXfontSize); // Include AxisX 
   
       if (e.X > leftInnerPlot && e.X < rightInnerPlot && 
        e.Y > topInnerPlot && e.Y < bottomInnerPlot) // return AxisX if inside the InnerPlot area or on AxisX 
        return currentArea.AxisX; 
       else if (e.X > (leftInnerPlot - axisYTickMarks - (int)Math.Round(axisYfontHeightSize)) && e.X < rightInnerPlot && 
         e.Y > topInnerPlot && e.Y < bottomInnerPlot) // return AxisY if on AxisY only 
        return currentArea.AxisY; 
   
       return null; 
   } 
   

如可以看出，該代碼比HitTest()更長。但運行時間爲較短。