void OnMessageLogged(object sender, LogEventArgs e)
{
if (!CheckAccess())
{
this.Dispatcher.BeginInvoke((Action)(() => LogMessage(e)));
}
else
{
LogMessage(e);
}
}
void LogMessage(LogEventArgs e)
{
int caret = this.CaretIndex;
int selectionStart = this.SelectionStart;
int selectionLength = this.SelectionLength;
bool scroll = (caret == this.Text.Length && selectionLength == 0);
var newText = e.Message;
if (newText.Length > MaxBufferSize)
{
this.Text = newText.Substring(newText.Length - MaxBufferSize);
scroll = true;
}
else if (newText.Length + this.Text.Length > MaxBufferSize)
{
int keep = Math.Min(MaxBufferSize - newText.Length, this.Text.Length);
int lost = this.Text.Length - keep;
this.Text = this.Text.Substring(lost) + newText;
if (lost >= caret && lost >= selectionStart)
{
scroll = true;
}
else
{
if (selectionLength > 0)
{
selectionStart -= lost;
}
caret -= lost;
}
}
else
{
this.Text = this.Text + newText;
}
if (scroll)
{
this.CaretIndex = this.Text.Length;
this.ScrollToEnd();
}
else
{
this.CaretIndex = caret;
if (selectionLength > 0)
{
this.SelectionStart = selectionStart;
this.SelectionLength = selectionLength;
}
}
}