Modifying default tab size in RichTextBox

Question

Is there any way to change the default tab size in a .NET RichTextBox? It currently seems to be set to the equivalent of 8 spaces which is kinda large for my taste.

Answer 1

It's strange that no one has proposed this method for all this time)

We can inherit from the RichTextBox and rewrite the CmdKey handler (ProcessCmdKey)
It will look like this:

public class TabRichTextBox : RichTextBox
{
    [Browsable(true), Category("Settings")]
    public int TabSize { get; set; } = 4;

    protected override bool ProcessCmdKey(ref Message Msg, Keys KeyData)
    {

        const int WM_KEYDOWN = 0x100;       // https://docs.microsoft.com/en-us/windows/desktop/inputdev/wm-keydown
        const int WM_SYSKEYDOWN = 0x104;    // https://docs.microsoft.com/en-us/windows/desktop/inputdev/wm-syskeydown
        // Tab has been pressed
        if ((Msg.Msg == WM_KEYDOWN || Msg.Msg == WM_SYSKEYDOWN) && KeyData.HasFlag(Keys.Tab))
        {
            // Let's create a string of spaces, which length == TabSize
            // And then assign it to the current position
            SelectedText += new string(' ', TabSize);

            // Tab processed
            return true;
        }
        return base.ProcessCmdKey(ref Msg, KeyData);
    }
}

Now, when you'll press Tab, a specified number of spaces will be inserted into the control area instead of \t