// Point is specified relative to the given visual
public static TextPointer ScreenPointToTextPointer(this FlowDocument document, Point screenPoint)
{
try
{
// Get text before point using automation
var peer = new DocumentAutomationPeer(document);
var textProvider = (ITextProvider)peer.GetPattern(PatternInterface.Text);
var rangeProvider = textProvider?.RangeFromPoint(screenPoint);
rangeProvider?.MoveEndpointByUnit(TextPatternRangeEndpoint.Start, TextUnit.Document, 1);
var charsBeforePoint = rangeProvider?.GetText(int.MaxValue)?.Length ?? 0;
// Find the pointer that corresponds to the TextPointer
var pointer = document.ContentStart.GetPositionAtOffset(charsBeforePoint);
// Adjust for difference between "text offset" and actual number of characters before pointer
for (var i = 0; i < 10; i++) // Limit to 10 adjustments
{
var error = charsBeforePoint - new TextRange(document.ContentStart, pointer).Text.Length;
if (error == 0)
{
break;
}
pointer = pointer?.GetPositionAtOffset(error);
}
return(pointer);
}
catch (Exception e)
{
Console.WriteLine(e);
return(null);
}
}
// Point is specified relative to the given visual
public static TextPointer ScreenPointToTextPointer(this FlowDocument document, Point screenPoint)
{
try
{
// Get text before point using automation
var peer = new DocumentAutomationPeer(document);
var textProvider = (ITextProvider)peer.GetPattern(PatternInterface.Text);
var rangeProvider = textProvider.RangeFromPoint(screenPoint);
// Try to use reflection to make retrieval of the pointer much faster
var member = rangeProvider.GetType().GetField("_start", System.Reflection.BindingFlags.NonPublic | System.Reflection.BindingFlags.Instance);
if (null != member)
{
var result = (TextPointer)member.GetValue(rangeProvider);
return(result);
}
else
{
// if reflection failed, we have to use the hard way
rangeProvider.MoveEndpointByUnit(TextPatternRangeEndpoint.Start, TextUnit.Document, 1);
int charsBeforePoint = rangeProvider.GetText(int.MaxValue).Length;
// Find the pointer that corresponds to the TextPointer
var pointer = document.ContentStart.GetPositionAtOffset(charsBeforePoint); // this is only a first guess
// Adjust for difference between "text offset" and actual number of characters before pointer
// Note that this is time consuming and can take some seconds (!) for big documents
for (int i = 0; i < 12; i++) // Limit to 12 adjustments
{
int error = charsBeforePoint - new TextRange(document.ContentStart, pointer).Text.Length;
if (error == 0)
{
break;
}
pointer = pointer.GetPositionAtOffset(error); // try to get the pointer iteratively
}
return(pointer);
}
}
catch (System.Exception ex)
{
return(null);
}
}
