RichTextBox syntax highlighting in real time--Disabling the repaint

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I'm creating a function that takes a RichTextBox and has access to a list of keywords & 'badwords'. I need to highlight any keywords & badwords I find in the RichTextBox while the user is typing, which means the function is called every time an editing key is released.

I've written this function, but the words and cursor in the box flicker too much for comfort.

I've discovered a solution--to disable the RichTextBox's ability to repaint itself while I'm editing and formatting its text. However, the only way I know to do this is to override the "WndProc" function and intercept (what I've been about to gather is) the repaint message as follows:

protected override void WndProc(ref System.Windows.Forms.Message m)
{
    if (m.Msg == 0x00f) {
         if (paint)
            base.WndProc(ref m);
         else
            m.Result = IntPtr.Zero;
    }
    else
         base.WndProc(ref m);
}

Where the boolean 'paint' is set to false just before I start highlighting and to true when I finish. But as I said, the function I make must take in a RichTextBox; I cannot use a subclass.

So, is there a way to disable the automatic repainting of a RichTextBox 'from the outside?'

richtextbox syntax-highlighting graphics c#
3 Answers

I haven't accumulated enough points to amend Hans' recommendation. So I added this Answer to mention that it may be necessary to request a repaint by calling InvalidateRect. Some Begin/End Update implementations do this automatically upon the final release of the update lock. Similarly in .Net, Control.Invalidate() can be called which invokes the native InvalidateRect function.

MSDN: Finally, the application can call the InvalidateRect function to cause the list box to be repainted.

See WM_SETREDRAW

user_2412960
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