Custom links in RichTextBox
Posted
by IVlad
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Published on 2010-04-02T15:54:09Z
Indexed on
2010/04/02
21:13 UTC
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Suppose I want every word starting with a #
to generate an event on double click. For this I have implemented the following test code:
private bool IsChannel(Point position, out int start, out int end)
{
if (richTextBox1.Text.Length == 0)
{
start = end = -1;
return false;
}
int index = richTextBox1.GetCharIndexFromPosition(position);
int stop = index;
while (index >= 0 && richTextBox1.Text[index] != '#')
{
if (richTextBox1.Text[index] == ' ')
{
break;
}
--index;
}
if (index < 0 || richTextBox1.Text[index] != '#')
{
start = end = -1;
return false;
}
while (stop < richTextBox1.Text.Length && richTextBox1.Text[stop] != ' ')
{
++stop;
}
--stop;
start = index;
end = stop;
return true;
}
private void richTextBox1_MouseMove(object sender, MouseEventArgs e)
{
textBox1.Text = richTextBox1.GetCharIndexFromPosition(new Point(e.X, e.Y)).ToString();
int d1, d2;
if (IsChannel(new Point(e.X, e.Y), out d1, out d2) == true)
{
if (richTextBox1.Cursor != Cursors.Hand)
{
richTextBox1.Cursor = Cursors.Hand;
}
}
else
{
richTextBox1.Cursor = Cursors.Arrow;
}
}
This handles detecting words that start with #
and making the mouse cursor a hand when it hovers over them. However, I have the following two problems:
- If I try to implement a double click event for
richTextBox1
, I can detect when a word is clicked, however that word is highlighted (selected), which I'd like to avoid. I can deselect it programmatically by selecting the end of the text, but that causes a flicker, which I would like to avoid. What ways are there to do this? - The
GetCharIndexFromPosition
method returns the index of the character that is closest to the cursor. This means that if the only thing my RichTextBox contains is a word starting with a#
then the cursor will be a hand no matter where on the rich text control it is. How can I make it so that it is only a hand when it hovers over an actual word or character that is part of a word I'm interested in? The implemented URL detection also partially suffers from this problem. If I enable detection of URLs and only writewww.test.com
in the rich text editor, the cursor will be a hand as long as it is on or below the link. It will not be a hand if it's to the right of the link however. I'm fine even with this functionality if making the cursor a hand if and only if it's on the text proves to be too difficult.
I'm guessing I'll have to resort to some sort of Windows API calls, but I don't really know where to start.
I am using Visual Studio 2008 and I would like to implement this myself.
Update: The flickering problem would be solved if I could make it so that no text is selectable through double clicking, only through dragging the mouse cursor. Is this easier to achieve? Because I don't really care if one can select text or not by double clicking in this case.
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