LinkLabel

/**
 * This is open-source software licensed under the terms of the MIT License.
 *
 * Copyright (c) 2023-2025 Petr Červinka - FortSoft <[email protected]>
 * Copyright (c) 2012 Hamid Sadeghian
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all
 * copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 * SOFTWARE.
 **
 * Version 1.2.0.0
 */

using System;
using System.Runtime.InteropServices;

namespace FortSoft.Controls.WinForms {

    /// <summary>
    /// Link label control that enforces the platform's native hand cursor
    /// (IDC_HAND) instead of the bitmap provided by <c>Cursors.Hand</c>.
    /// This ensures visual consistency with the operating system theme.
    /// </summary>
    public sealed class LinkLabel : System.Windows.Forms.LinkLabel {

        /// <summary>
        /// IDC_HAND from WinUser.h (0x7F89 == 32649).
        /// </summary>
        private const int IDC_HAND = 0x7F89;

        /// <summary>
        /// Loads a cursor resource.
        /// </summary>
        /// <param name="hInstance">
        /// A module handle to load the cursor from, or <see cref="IntPtr.Zero"/>
        /// to request a predefined system cursor (IDC_*).
        /// </param>
        /// <param name="lpCursorName">
        /// The resource identifier of the cursor. When <paramref name="hInstance"/>
        /// is <see cref="IntPtr.Zero"/>, pass the integer identifier of a predefined
        /// system cursor (for example <see cref="IDC_HAND"/>).
        /// </param>
        /// <returns>
        /// A handle to the cursor (<see cref="IntPtr"/>); returns
        /// <see cref="IntPtr.Zero"/> on failure.
        /// </returns>
        [DllImport("user32.dll", EntryPoint = "LoadCursorW", ExactSpelling = true)]
        private static extern IntPtr LoadCursor(IntPtr hInstance, int lpCursorName);

        /// <summary>
        /// Lazily created system hand cursor with safe fallback.
        /// </summary>
        private static readonly System.Windows.Forms.Cursor SystemHandCursor = CreateSystemHandCursor();

        /// <summary>
        /// Creates the system hand cursor or falls back to <c>Cursors.Hand</c>
        /// if the system cursor cannot be loaded.
        /// </summary>
        /// <returns>
        /// A <see cref="System.Windows.Forms.Cursor"/> representing the native
        /// hand cursor, or <c>Cursors.Hand</c> if loading fails.
        /// </returns>
        private static System.Windows.Forms.Cursor CreateSystemHandCursor() {
            IntPtr handle = LoadCursor(IntPtr.Zero, IDC_HAND);
            if (handle == IntPtr.Zero) {
                return System.Windows.Forms.Cursors.Hand;
            }
            return new System.Windows.Forms.Cursor(handle);
        }

        /// <summary>
        /// Replaces the base class hand cursor with the native system hand cursor
        /// when the mouse moves over the control and the base logic selects
        /// <c>Cursors.Hand</c>.
        /// </summary>
        /// <param name="e">
        /// Mouse event data provided by the Windows Forms event pipeline.
        /// </param>
        protected override void OnMouseMove(System.Windows.Forms.MouseEventArgs e) {
            base.OnMouseMove(e);
            if (OverrideCursor == System.Windows.Forms.Cursors.Hand) {
                OverrideCursor = SystemHandCursor;
            }
        }
    }
}