xenadmin/XenAdmin/Core/CueBannersManager.cs

/* Copyright (c) Citrix Systems, Inc. 
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using System;
using System.Runtime.InteropServices;
using System.Windows.Forms;

namespace XenAdmin.Core
{
    /// <summary>
    /// See http://www.ageektrapped.com/blog/the-missing-net-1-cue-banners-in-windows-forms-em_setcuebanner-text-prompt
    /// </summary>
    static class CueBannersManager
    {
        private const uint ECM_FIRST = 0x1500;
        private const uint EM_SETCUEBANNER = ECM_FIRST + 1;

        [DllImport("user32.dll", CharSet = CharSet.Auto, SetLastError = false)]
        static extern IntPtr SendMessage(IntPtr hWnd, uint Msg, uint wParam, [MarshalAs(UnmanagedType.LPWStr)] string lParam);

        [DllImport("user32.dll")]
        private static extern bool GetComboBoxInfo(IntPtr hwnd, ref COMBOBOXINFO pcbi);

        [StructLayout(LayoutKind.Sequential)]
        private struct COMBOBOXINFO
        {
            public int cbSize;
            public RECT rcItem;
            public RECT rcButton;
            public IntPtr stateButton;
            public IntPtr hwndCombo;
            public IntPtr hwndItem;
            public IntPtr hwndList;
        }

        [StructLayout(LayoutKind.Sequential)]
        private struct RECT
        {
            public int left;
            public int top;
            public int right;
            public int bottom;
        }

        public static void SetWatermark(TextBox textBox, string watermarkText)
        {
            SendMessage(textBox.Handle, EM_SETCUEBANNER, 0, watermarkText);
        }

        public static void SetWatermark(ComboBox comboBox, string watermarkText)
        {
            //a combobox is made up of three controls, a button, a list and textbox;
            //we want the textbox
            COMBOBOXINFO info = new COMBOBOXINFO();
            info.cbSize = Marshal.SizeOf(info);
            GetComboBoxInfo(comboBox.Handle, ref info);
            SendMessage(info.hwndItem, EM_SETCUEBANNER, 0, watermarkText);
        }
    }
}