public bool PreFilterMessage(ref Message m)
{
if ((WM)m.Msg == WM.MOUSEWHEEL)
{
// Only handle messages if the control belongs to our form.
Win32.POINT cursorPoint = new Win32.POINT();
Win32.GetCursorPos(ref cursorPoint);
IntPtr targetWindow = Win32.WindowFromPoint(cursorPoint);
Control control = Control.FromChildHandle(targetWindow);
if (control != null && ControlUtilities.ContainsControl(form.contentHeaderPanel, control))
{
// Forward the message to the control or the first of its parents which can have scrollbars.
while (control != null && !(control is ScrollableControl))
control = control.Parent;
if (control != null)
{
Win32.SendMessage(control.Handle, m.Msg, m.WParam, m.LParam);
return true;
}
}
}
return false;
}
/// <summary>
/// Sets the given bitmap as window content with transparent parts via the
/// layered windows API.
/// </summary>
/// <param name="bitmap">The bitmap to set.</param>
/// <param name="opacity">The overall opacity (255 = opaque).</param>
public static void SetBitmap(Control control, Bitmap bitmap, int opacity)
{
if (bitmap.PixelFormat != PixelFormat.Format32bppArgb)
throw new ApplicationException("The bitmap must be 32ppp with alpha-channel.");
IntPtr screenDc = Win32.GetDC(IntPtr.Zero);
IntPtr memDc = Win32.CreateCompatibleDC(screenDc);
IntPtr hBitmap = IntPtr.Zero;
IntPtr oldBitmap = IntPtr.Zero;
try
{
hBitmap = bitmap.GetHbitmap(Color.FromArgb(0)); // grab a GDI handle from this GDI+ bitmap
oldBitmap = Win32.SelectObject(memDc, hBitmap);
Win32.SIZE size = new Win32.SIZE(bitmap.Width, bitmap.Height);
Win32.POINT pointSource = new Win32.POINT(0, 0);
Win32.POINT topPos = new Win32.POINT(control.Left, control.Top);
Win32.BLENDFUNCTION blend = new Win32.BLENDFUNCTION();
blend.BlendOp = Win32.AC_SRC_OVER;
blend.BlendFlags = 0;
blend.SourceConstantAlpha = (byte)opacity;
blend.AlphaFormat = Win32.AC_SRC_ALPHA;
if (!control.IsDisposed && !control.Disposing)
{
Win32.UpdateLayeredWindow(control.Handle, screenDc, ref topPos, ref size, memDc,
ref pointSource, 0, ref blend, Win32.ULW_ALPHA);
}
}
finally
{
Win32.ReleaseDC(IntPtr.Zero, screenDc);
if (hBitmap != IntPtr.Zero)
{
Win32.SelectObject(memDc, oldBitmap);
Win32.DeleteObject(hBitmap);
}
Win32.DeleteDC(memDc);
}
}
