影响单个行的 WPF 多行文本框样式

Question

我需要制作一个多行文本框，在行长超过 80 个字符后更改字符的背景。因此，如果有人键入 85 个字符的句子，最后 5 个字符将具有黄色背景。我希望它使此功能成为风格的一部分，因为目前我们正在使用后面代码中的逻辑来执行此操作，并且当有人快速键入时它会滞后。

当前突出显示 IMLP

private void HighlightLines()
{
try
{
//// x is the distance in the row from the left side of the Textbox. e.g. Each character is one unit.
int x = 0;
//// y is the distance in the columns from the top of the Textbox. e.g. Each character is one unit.
int y = 0;
//// lines is the number of newline characters found in the Text.
int lines = 0;
//// Point 1 is the starting point of the range that needs to be highlighted.
TextPointer point1 = this.Document.ContentStart;
//// Point 2 is the end point of the range that needs to be highlighted.
TextPointer point2 = this.Document.ContentStart;
//// Range is the distance from Point 1 to Point 2 needed to apply the Yellow color to the area past 69 characters.
TextRange range;
//// Additional Ranges is the collection of all the ranges that need to be Yellow.
this.AdditionalRanges = new ObservableCollection<TextRange>();
//// Count the number of lines.
for (int i = 0; i < this.Text.Length; i++)
{
if (this.Text[i] == 'n')
{
lines++;
this.AdditionalRanges.Add(new TextRange(this.Document.ContentStart, this.Document.ContentEnd));
}
}
//// This map is used to differentiate which lines need to be colored. (True means the range is over 69 characters. False means the opposite).
bool[] map = new bool[lines];
//// Traverse the whole text.
for (int i = 0; i < this.Text.Length; i++)
{
var currentCharacter = this.Text[i];
var newLineCharacter = 'n';
if (currentCharacter == newLineCharacter)
{
var pointDifference = point1.GetOffsetToPosition(point2);
point1 = point1.GetPositionAtOffset(pointDifference);
x = 0;
y++;
}
else if (x > 69)
{
range = new TextRange(point1, point2);
this.AdditionalRanges[y] = range;
map[y] = true;
if (point2.GetNextInsertionPosition(LogicalDirection.Forward) != null)
{
point2 = point2.GetNextInsertionPosition(LogicalDirection.Forward);
}
}
else if (point1.GetNextInsertionPosition(LogicalDirection.Forward) != null && point2.GetNextInsertionPosition(LogicalDirection.Forward) != null)
{
point1 = point1.GetNextInsertionPosition(LogicalDirection.Forward);
point2 = point2.GetNextInsertionPosition(LogicalDirection.Forward);
x++;
}
}
//// Make everything white.
foreach (var item in this.AdditionalRanges)
{
item.ApplyPropertyValue(TextElement.BackgroundProperty, Brushes.White);
}
//// Make the appropriate ranges Yellow.
for (int i = 0; i < this.AdditionalRanges.Count; i++)
{
if (map[i])
{
this.AdditionalRanges[i].ApplyPropertyValue(TextElement.BackgroundProperty, Brushes.Yellow);
}
}
}
catch (Exception e)
{
// drop exception. this has only broke once and we dont exactly know why. 
}
}

Answer 1

它可能滞后，因为您的HighlightLines()方法每次都会扫描整个文档，我假设每次按键后都会调用它。理想情况下，您只想重新扫描已更改的文本部分。幸运的是，TextChanged 事件提供了更改的确切偏移量。

下面的示例代码是为使用 RichTextBox 而编写的，但您应该能够对其进行调整。此外，看起来您的代码正在检查 69 个字符而不是 80 个字符，因此这样做相同：

RichTextBox txt;
...
bool suppressChanges = false;
private void Txt_TextChanged(object sender, TextChangedEventArgs e)
{
if (!suppressChanges)
{
// suppress changes because changing highlights will trigger the event again
suppressChanges = true;
foreach (var change in e.Changes)
{
var changeStart = txt.Document.ContentStart.GetPositionAtOffset(change.Offset);
TextRange changedRange;
if (change.AddedLength > 0)
changedRange = new TextRange(changeStart, changeStart.GetPositionAtOffset(change.AddedLength));
else
changedRange = new TextRange(changeStart, changeStart);
SetRangeColors(changedRange);
}
//unsuppress changes
suppressChanges = false;
}
}
void SetRangeColors(TextRange range)
{
// Scan one line at a time starting with the beginning of the range
TextPointer current = range.Start.GetLineStartPosition(0);
while (current != null && current.CompareTo(range.End) < 0)
{
// find the next line or the end of the document
var nextLine = current.GetLineStartPosition(1, out int lines);
TextPointer lineEnd;
if (lines > 0)
lineEnd = nextLine.GetNextInsertionPosition(LogicalDirection.Backward);
else
lineEnd = txt.Document.ContentEnd;
var lineRange = new TextRange(current, lineEnd);
// clear properties first or the offsets won't match the characters
lineRange.ClearAllProperties();
var lineText = lineRange.Text;
if (lineText.Length > 69)
{
var highlight = new TextRange(current.GetPositionAtOffset(70), lineEnd);
highlight.ApplyPropertyValue(TextElement.BackgroundProperty, Brushes.Yellow);
}
// advance to the next line
current = lineEnd.GetLineStartPosition(1);
}
}