How to change the Enter KeyChar when pressed in a RichTextBox?-CodePudding

I am currently tasked with programming a text editor for some formatted text. I chose to use a RichTextBox for obvious reasons. For every key until now I was able to modify the KeyChar of it, either with overriding the ProcessCmdKey method or with subscribing to the KeyPress event or overriding the virtual method OnKeyPress.

The rtf text I use in this example is this:

{\rtf1\ansi\ansicpg1252\deff0\nouicompat\deflang1033{\fonttbl{\f0\fnil\fcharset0 Courier New;}{\f1\fnil Courier New;}{\f2\fnil Verdana;}} {\colortbl ;\red0\green0\blue0;} {*\generator Riched20 10.0.19041}\viewkind4\uc1 \pard\sa180\sl72\slmult1\ulc1\ul\b\f0\fs21 Header1:\ulc1\ulnone\b0\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\ul\b\f0 Header2:\ulc1\ulnone\b0\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\ul\b\f0 Header3:\ulc1\ulnone\b0\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\ulc1\f0 Lorem ipsum.\ulc1\f1\line\line\ulc1\f0 Signature...\ulc1\f2\fs20\par }

So with this rtf basically I am trying to simulate Shift Enter every time a user presses Enter, so that the line break is smaller than the default one when pressing Enter.

I declared my own RichTextBox for this, in hope I could dig in a bit deeper:

public class CustomRichTextBox : RichTextBox { ... }

To clarify what I tried so far - these were my approaches, which worked perfectly for normal chars:

using ProcessCmdKey to change the character A to B:

protected override bool ProcessCmdKey(ref Message m, Keys keyData)
{
    if(keyData == Keys.A)
    {
        m.WParam = new IntPtr((int)Keys.B);
        return base.ProcessCmdKey(ref m, Keys.B);
    }
    else if(keyData == (Keys.Shift | Keys.A))
    {
        m.WParam = new IntPtr((int)(Keys.Shift | Keys.B));
        return base.ProcessCmdKey(ref m, (Keys.Shift | Keys.B));
    }

    return base.ProcessCmdKey(ref m, keyData);
}

using OnKeyPress to change the character A to B:

protected override void OnKeyPress(KeyPressEventArgs e)
{
    if(e.KeyChar == 'A')
    {
        e.KeyChar = 'B';
    }
    else if(e.KeyChar == 'a')
    {
        e.KeyChar = 'b';
    }

    base.OnKeyPress(e);
}

Only for me pressing Enter, it doesn't work as expected (no effect for me):

protected override bool ProcessCmdKey(ref Message m, Keys keyData)
{
    if (keyData == Keys.Enter)
    {
        m.WParam = new IntPtr((int)(Keys.Shift | Keys.Enter));
        return base.ProcessCmdKey(ref m, (Keys.Shift | Keys.Enter));
    }

    return base.ProcessCmdKey(ref m, keyData);
}

Is there no simple way to realize this or did I miss something?

Edit:

I forgot to include the approach with OnKeyPress. Here is what I tried:

protected override void OnKeyPress(KeyPressEventArgs e)
{
     if(e.KeyChar == '\r')
     {
         e.KeyChar = '\u2028';
     }

     base.OnKeyPress(e);
}

And here the result:

CodePudding user response：

As it turned out, it was embarassingly easy to realize with using SendKeys and blocking the Enter KeyPress by returning true...

private bool sendingEnter = false;

public override bool PreProcessMessage(ref Message msg)
{
    if(msg.Msg == WM_KEYDOWN && msg.WParam.ToInt32() == VK_RETURN)
    {
        if (!sendingEnter)
        {
            sendingEnter = true;
            SendKeys.Send(" {ENTER}");
            return true;
        }
        else
        {
            sendingEnter = false;
        }
    }

    return base.PreProcessMessage(ref msg);
}