WinForm中的重绘 - 文本的重绘

• 两种方式
  • TextRenderer.DrawText
    
    • 注意：默认在每次绘制的文本左右有padding，即使参数中设置了TextFormatFlags.NoPadding也是一样，因此在分段绘制文本时（比如绘制搜索结果文本中高亮一部分时），每次绘制前在定位传递Point参数时，需要进行修正，减去相应个数的padding的宽度（由于需要转成int，所以会有误差）
      • https://theartofdev.com/2013/08/12/the-wonders-of-text-rendering-and-gdi/
        
      •  
  • e.Graphics.DrawString

 1         private void smartTipListBox_DrawItem(object sender, DrawItemEventArgs e)
 2         {
 3             ListBox eObj = sender as ListBox;
 4 
 5             e.DrawBackground();
 6 
 7             string entireText = ((EntireInfo)eObj.Items[e.Index]).VarName;
 8 
 9             int index = entireText.IndexOf(searchingStr, StringComparison.InvariantCultureIgnoreCase);
10             if (index >= 0)
11             {
12                 TextFormatFlags formatFlags = TextFormatFlags.NoPadding | TextFormatFlags.SingleLine;
13                 //TextFormatFlags formatFlags = TextFormatFlags.TextBoxControl | TextFormatFlags.WordBreak;
14                 int leftAndTopPadding = 5;
15                 string headText = entireText.Substring(0, index);
16                 string matchedText = entireText.Substring(index, searchingStr.Length);
17                 string tailText = entireText.Substring(index + matchedText.Length, entireText.Length - index - matchedText.Length);
18                 int headTextPartWidth = TextRenderer.MeasureText(headText, e.Font, new Size(int.MaxValue, int.MaxValue), formatFlags).Width;
19                 int highlightedTextWidth = TextRenderer.MeasureText(matchedText, e.Font, new Size(int.MaxValue, int.MaxValue), formatFlags).Width;
20                 int yPosition = e.Index * smartTipListBox.ItemHeight + leftAndTopPadding;
21                 int leftTextMargin = (int)(1 * e.Font.GetHeight() / 6);
22                 int rightTextMargin = (int)(1 * e.Font.GetHeight() / 4);
23                 if (index > 0)
24                 {
25                     TextRenderer.DrawText(e.Graphics, headText, e.Font, new Point(leftAndTopPadding, yPosition), Color.Black, formatFlags);
26                     TextRenderer.DrawText(e.Graphics, matchedText, e.Font, new Point(leftAndTopPadding + headTextPartWidth - 2 * leftTextMargin - rightTextMargin, yPosition), Color.Red, formatFlags);
27                     TextRenderer.DrawText(e.Graphics, tailText, e.Font, new Point(leftAndTopPadding + headTextPartWidth + highlightedTextWidth - 3 * leftTextMargin - 2 * rightTextMargin, yPosition), Color.Black, formatFlags);
28                 }
29                 else
30                 {
31                     TextRenderer.DrawText(e.Graphics, matchedText, e.Font, new Point(leftAndTopPadding + headTextPartWidth, yPosition), Color.Red, formatFlags);
32                     TextRenderer.DrawText(e.Graphics, tailText, e.Font, new Point(leftAndTopPadding + headTextPartWidth + highlightedTextWidth - 2 * leftTextMargin - rightTextMargin, yPosition), Color.Black, formatFlags);
33                 }
34 
35                 //Brush blackBrush = Brushes.Black;
36                 //Brush redBrush = Brushes.Red;
37                 //Rectangle initRectangle = e.Bounds;
38                 //e.Graphics.DrawString(entireText.Substring(0, index), e.Font, blackBrush, initRectangle, null);
39                 //initRectangle.Offset(Convert.ToInt32(e.Graphics.MeasureString(entireText.Substring(0, index), e.Font).Width), 0);
40                 //e.Graphics.DrawString(entireText.Substring(index, searchingStr.Length), e.Font, redBrush, initRectangle, null);
41                 //initRectangle.Offset(Convert.ToInt32(e.Graphics.MeasureString(entireText.Substring(index, searchingStr.Length), e.Font).Width), 0);
42                 //e.Graphics.DrawString(entireText.Substring(index + searchingStr.Length, entireText.Length - index - searchingStr.Length), e.Font, blackBrush, initRectangle, null);
43             }
44         }