Suppress line break in a RichTextBox at certain positions

Question

I need to suppress some linebreaks in a RichTextBox.

For example, consider d6+. There must not be a line break between 6 and +. Basically I'm looking for something like <nobr> in HTML.

So far, I've messed around with inserting \u+FEFF etc (which worked on some machines, but some showed vertical lines, maybe a font problem although windows standard font). I also tried to manipulate the rtf directly, i.e. box.rtf = ... with putting some \zwnbo in there, but I never seem to get it right.

Help much appreciated.

Answer 1

Yes, you can use all of the RichText API with your RichTextBox control.

You may be interested take a look at the following sites:

http://www.pinvoke.net/default.aspx/user32.sendmessage - how to send messages to windows using p/invoke.

You can use the Handle property of the RichTextBox to get the window handle of that control, and then send messages to it.

Also look at these include files shiped with SDK from Microsoft, thaty are not going to be used directly in C#, but these files constains all constants you may have to use, such as WB_ISDELIMITER, WB_CLASSIFY and others.

• winuser.h
• richedit.h

In the following example I demonstrate how to use the APIs provided.

EDIT:

This new sample has code marked as unsafe, but it is better because it does not suffer from the problem of single character string, since I can have a char* parameter and manipulate it. The old sample follows this one:

This is C# code, not C++... to compile it you will have to go to project options and mark the check-box to allow unsafe code to run.

Right click the project -> Properties (Alt+Enter) -> Build -> General -> Allow unsafe code (must be checked)

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace q6359774
{
    class MyRichTextBox : RichTextBox
    {
        const int EM_SETWORDBREAKPROC = 0x00D0;
        const int EM_GETWORDBREAKPROC = 0x00D1;

        protected override void OnHandleCreated(EventArgs e)
        {
            base.OnHandleCreated(e);
            this.Text = "abcdefghijklmnopqrstuvwxyz-abcdefghijklmnopqrstuvwxyz";
            NewMethod();
        }

        unsafe private void NewMethod()
        {
            if (!this.DesignMode)
                SendMessage(this.Handle, EM_SETWORDBREAKPROC, IntPtr.Zero, Marshal.GetFunctionPointerForDelegate(new EditWordBreakProc(MyEditWordBreakProc)));
        }

        [DllImport("User32.DLL")]
        public static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

        unsafe delegate int EditWordBreakProc(char* lpch, int ichCurrent, int cch, int code);

        unsafe int MyEditWordBreakProc(char* lpch, int ichCurrent, int cch, int code)
        {
            const int WB_ISDELIMITER = 2;
            const int WB_CLASSIFY = 3;
            if (code == WB_ISDELIMITER)
            {
                char ch = *lpch;
                return ch == '-' ? 0 : 1;
            }
            else if (code == WB_CLASSIFY)
            {
                char ch = *lpch;
                var vResult = Char.GetUnicodeCategory(ch);
                return (int)vResult;
            }
            else
            {
                var lpch2 = lpch;
                // in this case, we must find the begining of a word:
                for (int it = ichCurrent; it < cch; it++)
                {
                    char ch = *lpch2;
                    if (it + 1 < cch && lpch2[0] == '-' && lpch2[1] != '-')
                        return it;
                    if (lpch2[0] == '\0')
                        return 0;
                    lpch2++;
                }
            }

            return 0;
        }
    }
}

Old Sample Code

The sample consists of a class that inherits from RichTextBox and places a custom handler using EM_SETWORDBREAKPROC. This class will only break lines exactly when over '-' character. Not before, nor after.

using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace q6359774
{
    class MyRichTextBox : RichTextBox
    {
        const int EM_SETWORDBREAKPROC = 0x00D0;
        const int EM_GETWORDBREAKPROC = 0x00D1;

        protected override void OnHandleCreated(EventArgs e)
        {
            base.OnHandleCreated(e);
            this.Text = "abcdefghijklmnopqrstuvwxyz-abcdefghijklmnopqrstuvwxyz";
            if (!this.DesignMode)
                SendMessage(this.Handle, EM_SETWORDBREAKPROC, IntPtr.Zero, Marshal.GetFunctionPointerForDelegate(new EditWordBreakProc(MyEditWordBreakProc)));
        }

        [DllImport("User32.DLL")]
        public static extern IntPtr SendMessage(IntPtr hWnd, UInt32 Msg, IntPtr wParam, IntPtr lParam);

        delegate int EditWordBreakProc(string lpch, int ichCurrent, int cch, int code);

        int MyEditWordBreakProc(string lpch, int ichCurrent, int cch, int code)
        {
            const int WB_ISDELIMITER = 2;
            const int WB_CLASSIFY = 3;
            if (code == WB_ISDELIMITER)
            {
                if (lpch.Length == 0 || lpch == null) return 0;
                char ch = lpch[ichCurrent];
                return ch == '-' ? 0 : 1;
            }
            else if (code == WB_CLASSIFY)
            {
                if (lpch.Length == 0 || lpch == null) return 0;
                char ch = lpch[ichCurrent];
                var vResult = Char.GetUnicodeCategory(ch);
                return (int)vResult;
            }
            else
            {
                if (lpch.Length == 0 || lpch == null) return 0;
                for (int it = ichCurrent; it < lpch.Length; it++)
                {
                    char ch = lpch[it];
                    if (ch != '-') return it;
                }
            }

            return 0;
        }
    }
}

It is just a draft, so you may have to further improve it, so you can achieve your goals.

Place the control in a windows form, and run.

Resize the window and see if this is what you want to do!

You will have to make the seeking of word boundaries... I didn't manage to make it work yet.