WPF開発ノウハウ集

Windowのタイトルバーにヘルプアイコンを実装する

以下のコードをWindowのXaml.csに実装する

public partial class MainWindow : Window
{
    private const uint WS_EX_CONTEXTHELP = 0x00000400;
    private const uint WS_MINIMIZEBOX = 0x00020000;
    private const uint WS_MAXIMIZEBOX = 0x00010000;
    private const int GWL_STYLE = -16;
    private const int GWL_EXSTYLE = -20;
    private const int SWP_NOSIZE = 0x0001;
    private const int SWP_NOMOVE = 0x0002;
    private const int SWP_NOZORDER = 0x0004;
    private const int SWP_FRAMECHANGED = 0x0020;
    private const int WM_SYSCOMMAND = 0x0112;
    private const int SC_CONTEXTHELP = 0xF180;

    [DllImport( "user32.dll" )]
    private static extern uint GetWindowLong( IntPtr hwnd, int index );

    [DllImport( "user32.dll" )]
    private static extern int SetWindowLong( IntPtr hwnd, int index, uint newStyle );

    [DllImport( "user32.dll" )]
    private static extern bool SetWindowPos( IntPtr hwnd, IntPtr hwndInsertAfter, int x, int y, int width, int height, uint flags );

    protected override void OnSourceInitialized( EventArgs e ) 
    {
        base.OnSourceInitialized( e );
        IntPtr hwnd = new System.Windows.Interop.WindowInteropHelper( this ).Handle;
        uint styles = GetWindowLong( hwnd, GWL_STYLE );
        styles &= 0xFFFFFFFF ^ ( WS_MINIMIZEBOX | WS_MAXIMIZEBOX );
        SetWindowLong( hwnd, GWL_STYLE, styles );
        styles = GetWindowLong( hwnd, GWL_EXSTYLE );
        styles |= WS_EX_CONTEXTHELP;
        SetWindowLong( hwnd, GWL_EXSTYLE, styles );
        SetWindowPos( hwnd, IntPtr.Zero, 0, 0, 0, 0, SWP_NOMOVE | SWP_NOSIZE | SWP_NOZORDER | SWP_FRAMECHANGED );
        ( ( HwndSource )PresentationSource.FromVisual( this ) ).AddHook( this.HelpHook );
    }

    private IntPtr HelpHook( IntPtr hwnd, int msg, IntPtr wParam, IntPtr lParam, ref bool handled ) 
    {
        if( msg == WM_SYSCOMMAND && ( ( int )wParam & 0xFFF0 ) == SC_CONTEXTHELP ) 
        {
            <ここにHelpアイコンクリック時の処理を実装する>
            handled = true;
        }
        return IntPtr.Zero;
    }
}