文本和边框之间的富文本框填充

是否可以在文本和边框之间的富文本框控件中添加填充？

我尝试将一个富文本框停靠在面板内，并将所有四个边的填充设置为 10，这实现了我想要的效果。除非需要富文本框的垂直滚动条，该滚动条也会被填充。

有EM_GETRECT https://learn.microsoft.com/en-us/windows/desktop/Controls/em-getrect and EM_SETRECT https://learn.microsoft.com/en-us/windows/desktop/Controls/em-setrect.

将这两者结合在一起，你可以做到这一点：

...看起来像这样：

我写过一个小的 C# 扩展类 http://pastebin.com/FnEGqWxX结束这一切。

使用示例：

const int dist = 24;
richTextBox1.SetInnerMargins(dist, dist, dist, 0);

这会将左、上、右内边距设置为 24，将底部留为零。

请注意，滚动时，上边距保持设置状态，如下所示：

就我个人而言，这对我来说看起来“不自然”。我希望滚动时顶部边距也变为零。

也许有一个解决方法......

完整源代码

根据要求：

public static class RichTextBoxExtensions
{
    public static void SetInnerMargins(this TextBoxBase textBox, int left, int top, int right, int bottom)
    {
        var rect = textBox.GetFormattingRect();

        var newRect = new Rectangle(left, top, rect.Width - left - right, rect.Height - top - bottom);
        textBox.SetFormattingRect(newRect);
    }

    [StructLayout(LayoutKind.Sequential)]
    private struct RECT
    {
        public readonly int Left;
        public readonly int Top;
        public readonly int Right;
        public readonly int Bottom;

        private RECT(int left, int top, int right, int bottom)
        {
            Left = left;
            Top = top;
            Right = right;
            Bottom = bottom;
        }

        public RECT(Rectangle r) : this(r.Left, r.Top, r.Right, r.Bottom)
        {
        }
    }

    [DllImport(@"User32.dll", EntryPoint = @"SendMessage", CharSet = CharSet.Auto)]
    private static extern int SendMessageRefRect(IntPtr hWnd, uint msg, int wParam, ref RECT rect);

    [DllImport(@"user32.dll", EntryPoint = @"SendMessage", CharSet = CharSet.Auto)]
    private static extern int SendMessage(IntPtr hwnd, int wMsg, IntPtr wParam, ref Rectangle lParam);

    private const int EmGetrect = 0xB2;
    private const int EmSetrect = 0xB3;

    private static void SetFormattingRect(this TextBoxBase textbox, Rectangle rect)
    {
        var rc = new RECT(rect);
        SendMessageRefRect(textbox.Handle, EmSetrect, 0, ref rc);
    }

    private static Rectangle GetFormattingRect(this TextBoxBase textbox)
    {
        var rect = new Rectangle();
        SendMessage(textbox.Handle, EmGetrect, (IntPtr) 0, ref rect);
        return rect;
    }
}