滚动 DataGridView 的合并标题单元格时出现问题 [英] Problem while scrolling merged Header Cells of a DataGridView

问题描述

在我的 WinForm 项目中，我有一个 DataGridView 控件.
我实现了合并 2 列的标题单元格.它工作正常，但滚动时出现问题.下面的图片应该可以解释它.
有人可以帮忙吗?

这是我用来合并列标题单元格的代码.
合并后的Columns的索引为20和21.

private void loadEvents(){this.dgv_db_door.Paint += new PaintEventHandler(dgv_db_door_Paint);this.dgv_db_door.Scroll += new ScrollEventHandler(dgv_db_door_Scroll);this.dgv_db_door.ColumnWidthChanged += DataGridView1_ColumnWidthChanged;this.dgv_db_door.Resize += DataGridView1_Resize;}私有无效 dgv_db_door_Paint(对象发送者，PaintEventArgs e){字符串 doorCloser = "DOOR CLOSE";//合并列ara 20和21的索引号；int 合并列 1 = 20；int 合并列 2 = 21；矩形 r1 = dgv_db_door.GetCellDisplayRectangle(mergedColumn1, -1, true);int w2 = dgv_db_door.GetCellDisplayRectangle(mergedColumn2, -1, true).Width;r1.X += 1;r1.Y += 1;r1.Width = r1.Width + w2 - 2;r1.Height = r1.Height/2 - 2;e.Graphics.FillRectangle(new SolidBrush(dgv_db_door.ColumnHeadersDefaultCellStyle.BackColor), r1);StringFormat 格式 = new StringFormat();format.Alignment = StringAlignment.Center;format.LineAlignment = StringAlignment.Center;e.Graphics.DrawString(doorCloser, dgv_db_door.ColumnHeadersDefaultCellStyle.Font,新的 SolidBrush(dgv_db_door.ColumnHeadersDefaultCellStyle.ForeColor)，r1，格式)；}私人无效 dgv_db_door_Scroll(对象发送者，ScrollEventArgs e){如果(e.OldValue > e.NewValue){}别的{this.InvalidateHeader();}}private void DataGridView1_Resize(对象发送者，EventArgs e){this.InvalidateHeader();}private void DataGridView1_ColumnWidthChanged(对象发送者，DataGridViewColumnEventArgs e){this.InvalidateHeader();}私有无效 InvalidateHeader(){矩形 rtHeader = this.dgv_db_door.DisplayRectangle;rtHeader.Height = this.dgv_db_door.ColumnHeadersHeight/2;this.dgv_db_door.Invalidate(rtHeader);}

解决方案

对绘图程序的一些修改:

• 自定义标题绘制矩形的大小计算指定范围内所有列的宽度.
• 绘图区域的位置是使用最左侧列的位置计算的，

  ---

  使用 System.Reflection;TextFormatFlags centerTopflags =TextFormatFlags.Horizo​​ntalCenter |TextFormatFlags.Top |TextFormatFlags.PreserveGraphicsClipping;字符串mergedHeaderText = string.Empty;int[] 合并列 = null;public void SomeForm(){this.InitializeComponent();var flags = BindingFlags.Instance |BindingFlags.NonPublic;dgvTest.GetType().GetProperty(DoubleBuffered", flags).SetValue(dgvTest, true);合并列 = 新 int[] { 20, 21 };mergeHeaderText = "DOOR CLOSE";}私有无效 dgv_db_door_Paint(对象发送者，PaintEventArgs e){var dgv = 发送方为 DataGridView；var headerStyle = dgv.ColumnHeadersDefaultCellStyle;int colsWidth = -1;int colsLeft = 1;//合并列范围的绝对宽度for (int i = 0; i  0){colsLeft += dgv.Columns.OfType().Where(c => c.Visible).Take(mergedColumns[0]).Sum(c => c.Width);}//合并标题原始绘制矩形var r = 新矩形(dgv.RowHeadersWidth + colsLeft - dgv.Horizo​​ntalScrollingOffset, 2,colsWidth, dgv.ColumnHeadersHeight);//测量要渲染的文本的高度 - 不换行r.Height = TextRenderer.MeasureText(e.Graphics,mergedHeaderText,headerStyle.Font,r.Size,centerTopflags).Height;//仅在屏幕上可见时绘制合并的标题if (r.Right > dgv.RowHeadersWidth || r.X < dgv.DisplayRectangle.Right) {//裁剪绘图区域以排除行标题var clipRect = 新矩形(dgv.RowHeadersWidth + 1, 0,dgv.DisplayRectangle.Width - dgv.RowHeadersWidth, dgv.ColumnHeadersHeight);e.Graphics.SetClip(clipRect);使用 (var Brush = new SolidBrush(headerStyle.BackColor)) e.Graphics.FillRectangle(brush, r);TextRenderer.DrawText(e.Graphics,mergedHeaderText,headerStyle.Font,r,headerStyle.ForeColor,centerTopflags);e.Graphics.ResetClip();}}

  In my WinForm project I have a DataGridView control.
  I achieved to merge the Header cells of 2 Columns. It is working fine but there is a problem when scrolling. The image below should explain it.
  Can anyone help?

  This is the code I use to merging the Column Header cells.
  The indexes of the merged Columns are 20 and 21.

  private void loadEvents()
  {
      this.dgv_db_door.Paint += new PaintEventHandler(dgv_db_door_Paint);
      this.dgv_db_door.Scroll += new ScrollEventHandler(dgv_db_door_Scroll);
      this.dgv_db_door.ColumnWidthChanged += DataGridView1_ColumnWidthChanged;
      this.dgv_db_door.Resize += DataGridView1_Resize;
  }
  
  private void dgv_db_door_Paint(object sender, PaintEventArgs e)
  {
       string doorCloser = "DOOR CLOSER";
      
       //Index numbers of merged columns ara 20 and 21;
       int mergedColumn1 = 20;
       int mergedColumn2 = 21;
       Rectangle r1 = dgv_db_door.GetCellDisplayRectangle(mergedColumn1, -1, true);
       int w2 = dgv_db_door.GetCellDisplayRectangle(mergedColumn2, -1, true).Width;
       r1.X += 1;
       r1.Y += 1;
       r1.Width = r1.Width + w2 - 2;
       r1.Height = r1.Height / 2 - 2;
       e.Graphics.FillRectangle(new SolidBrush(dgv_db_door.ColumnHeadersDefaultCellStyle.BackColor), r1);
      
      StringFormat format = new StringFormat();
      
      format.Alignment = StringAlignment.Center;
      format.LineAlignment = StringAlignment.Center;
      e.Graphics.DrawString(doorCloser, dgv_db_door.ColumnHeadersDefaultCellStyle.Font,
      new SolidBrush(dgv_db_door.ColumnHeadersDefaultCellStyle.ForeColor), r1, format);
                   
  }
  private void dgv_db_door_Scroll(object sender, ScrollEventArgs e)
  {
      if (e.OldValue > e.NewValue)
      {
                  
      }
      else
      {
          this.InvalidateHeader();
      }
  }
  
  private void DataGridView1_Resize(object sender, EventArgs e)
  {
      this.InvalidateHeader();
  }
      
  private void DataGridView1_ColumnWidthChanged(object sender, DataGridViewColumnEventArgs e)
  {
       this.InvalidateHeader();
  }
  
  private void InvalidateHeader()
  {
       Rectangle rtHeader = this.dgv_db_door.DisplayRectangle;
       rtHeader.Height = this.dgv_db_door.ColumnHeadersHeight / 2;
      this.dgv_db_door.Invalidate(rtHeader);
  }
  

  解决方案

  A few modifications to the drawing procedure:

  • The custom Header drawing Rectangle is sized calculating the Width of all the Columns in the specified Range.
  • The position of the drawing area is calculated using the left-most Column's position, the RowHeadersWidth and the current DataGridView.HorizontalScrollingOffset, which defines the horizontal scroll position of the client rectangle.
  • To draw the custom Header, a clipping region is created - using Graphics.SetClip() - to exclude the Row Header from the drawing area.
  • The custom Header is only rendered when visible on screen.
  • I'm using TextRenderer.DrawText instead of Graphics.DrawString(), since this is the method used by this control to render its content.
  • Hence, I'm calculating the height of the text bounds using TextRenderer.MeasureText()
  • TextFormatFlags.PreserveGraphicsClipping is used to instruct TextRenderer not to draw the text outside the clipping region of the Graphics object.

  Note 1: I've added Double-Buffering to the DataGridView, to avoid any flickering when clicking the Header Cells. It may have an impact when the grid needs to render a high number of Rows.

  Note 2: You can remove all those InvalidateHeader() calls, not needed here.

  ► This new behavior allows to reset the range of Columns to include in the custom Header and the Header's Text at any time (as shown in the visual example).

  ---

  This is how it looks now:

  ---

  using System.Reflection;
  
  TextFormatFlags centerTopflags = 
      TextFormatFlags.HorizontalCenter | TextFormatFlags.Top | TextFormatFlags.PreserveGraphicsClipping;
  string mergedHeaderText = string.Empty;
  int[] mergedColumns = null; 
  
  public void SomeForm()
  {
      this.InitializeComponent();
      var flags = BindingFlags.Instance | BindingFlags.NonPublic;
      dgvTest.GetType().GetProperty("DoubleBuffered", flags).SetValue(dgvTest, true);
      mergedColumns = new int[] { 20, 21 };
      mergedHeaderText = "DOOR CLOSER"
  }
  
  private void dgv_db_door_Paint(object sender, PaintEventArgs e)
  {
      var dgv = sender as DataGridView;
      var headerStyle = dgv.ColumnHeadersDefaultCellStyle;
      int colsWidth = -1;
      int colsLeft = 1;
  
      // Absolute Width of the merged Column range
      for (int i = 0; i < mergedColumns.Length; i++) {
          var col = dgv.Columns[mergedColumns[i]];
          colsWidth += col.Visible ? col.Width : 0;
      }
  
      // Absolute Left position of the first Column to merge
      if (mergedColumns[0] > 0) {
          colsLeft += dgv.Columns.OfType<DataGridViewColumn>()
              .Where(c => c.Visible).Take(mergedColumns[0]).Sum(c => c.Width);
      }
  
      // Merged Headers raw drawing  Rectangle
      var r = new Rectangle(
          dgv.RowHeadersWidth + colsLeft - dgv.HorizontalScrollingOffset, 2, 
          colsWidth, dgv.ColumnHeadersHeight);
  
      // Measure the Height of the text to render - no wrapping
      r.Height = TextRenderer.MeasureText(e.Graphics, mergedHeaderText, headerStyle.Font, r.Size, centerTopflags).Height;
  
      // Draw the merged Headers only if visible on screen
      if (r.Right > dgv.RowHeadersWidth || r.X < dgv.DisplayRectangle.Right) {
          // Clip the drawing Region to exclude the Row Header
          var clipRect = new Rectangle(
              dgv.RowHeadersWidth + 1, 0, 
              dgv.DisplayRectangle.Width - dgv.RowHeadersWidth, dgv.ColumnHeadersHeight);
          e.Graphics.SetClip(clipRect);
  
          using (var brush = new SolidBrush(headerStyle.BackColor)) e.Graphics.FillRectangle(brush, r);
          TextRenderer.DrawText(e.Graphics, mergedHeaderText, headerStyle.Font, r, headerStyle.ForeColor, centerTopflags);
          e.Graphics.ResetClip();
      }
  }
  

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