Implementing search&highlight - how can I avoid delays when highlight is slow?

问题

I have a RichText, and want to implement a highlighting search, like you see in VS or Chrome. I got a fairly-working implementation going:

private void _txtSearch_TextChanged(object sender, EventArgs e)
{
    new RichTextNode(richTextBox1).Highlight(_txtSearch.Text);
}

public void Highlight(string text)
{
    textBox.BeginUpdate();   // Extension, implemented with P/Invoke

    textBox.SelectionStart = 0;
    textBox.SelectionLength = textBox.Text.Length;
    textBox.SelectionBackColor = textBox.BackColor;

    int highlights = 0;

    if (!string.IsNullOrEmpty(text))
    {
    int pos = 0;

    string boxText = textBox.Text;
    while ((pos = boxText.IndexOf(text, pos, StringComparison.OrdinalIgnoreCase)) != -1 && (highlights++) < 500)
    {
        textBox.SelectionStart = pos;
        textBox.SelectionLength = text.Length;

        textBox.SelectionBackColor = Color.Yellow;
        pos += text.Length;
    }
    }

    textBox.EndUpdate();  // Extension, implemented with P/Invoke
}

However, I want to support large amounts of text - up to 2MB. When there's a lot of text, each such update takes 250ms. That's OK for a single search - however, my search is incremental, which means that if the user type a 10-letter work, each letter appears after 250ms, which looks bad.

I implemented a wait using a timer:

private void _txtSearch_TextChanged(object sender, EventArgs e)
{
    performSearch.Stop();
    performSearch.Interval = 100; // Milliseconds
    performSearch.Start();
}

private void performSearch_Tick(object sender, EventArgs e)
{
    new RichTextNode(richTextBox1).Highlight(_txtSearch.Text);
    performSearch.Stop();
}

This works fairly well. However, it slows down the incremental search when the text is short, which is sub-optimal. I guess I could count the chars, but that feels like a hack...

Ideally, I'd like not to highlight when additional keystrokes are coming:

private void _txtSearch_TextChanged(object sender, EventArgs e)
{
    if (!_txtSearch.Magic_are_additional_TextChanged_events_already_queued())
        new RichTextNode(richTextBox1).Highlight(_txtSearch.Text);
}

Is there a way to do this? Or is the timer solution the best I can hope for?

回答1:

I ended up using the timer solution described in the question, with a delay of 1ms.

来源：https://stackoverflow.com/questions/15587767/implementing-searchhighlight-how-can-i-avoid-delays-when-highlight-is-slow

标签

winforms

asynchronous

richtextbox