Custom Caret for WinForms TextBox

Question

I'm developing a custom HyperTerminal like application in a WinForms .Net 2.0 application. I have a multiline TextBox in a Panel in which you can interact with a hardware device.

My customer wants to have a custom Caret, a filled rectangle the size of one character space instead of the vertical line that is by default.

I know .Net does not provide an option to do this by default, but there must some Windows function to do it.

Answer 1

These are the list of Native Caret functions provided by Windows you can use them for you application.

    [DllImport("User32.dll")]
    static extern bool CreateCaret(IntPtr hWnd, int hBitmap, int nWidth, int nHeight);

    [DllImport("User32.dll")]
    static extern bool SetCaretPos(int x, int y);

    [DllImport("User32.dll")]
    static extern bool DestroyCaret();

    [DllImport("User32.dll")]
    static extern bool ShowCaret(IntPtr hWnd);

    [DllImport("User32.dll")]
    static extern bool HideCaret(IntPtr hWnd);

Refer SharpDevelop, Source Code @ src\Libraries\ICSharpCode.TextEditor\Project\Src\Gui\Caret.cs

Answer 2

Assume a form with a textbox on it:

public partial class Form1 : Form
{
    [DllImport("user32.dll")]
    static extern bool CreateCaret(IntPtr hWnd, IntPtr hBitmap, int nWidth, int nHeight);
    [DllImport("user32.dll")]
    static extern bool ShowCaret(IntPtr hWnd);

    public Form1()
    {
        InitializeComponent();
    }

    private void Form1_Shown(object sender, EventArgs e)
    {
        CreateCaret(textBox1.Handle, IntPtr.Zero, 10, textBox1.Height);
        ShowCaret(textBox1.Handle);
    }
}

Answer 3

I would use System.Drawing to draw a custom cursor (bitmap), maybe with a timer to let it blink like another cursor.

Get the current position of the Cursor in pixels and draw a bitmap over that cursor. Can be tricky to find the correct position, but should be doable.

Have a look here for Owner drawn textbox in winforms.