private void InitializeThumbnail()
{
if (IntPtr.Zero != _thumb)
{
// release the old thumbnail
ReleaseThumbnail();
}
if (IntPtr.Zero == Handle)
{
return;
}
// find our parent hwnd
_target = (HwndSource)HwndSource.FromVisual(this);
// if we have one, we can attempt to register the thumbnail
if (_target == null || 0 != DwmUtils.DwmRegisterThumbnail(_target.Handle, Handle, out this._thumb))
{
return;
}
DwmThumbnailProperties props = new DwmThumbnailProperties();
props.Visible = false;
props.SourceClientAreaOnly = false;
props.Opacity = (byte)(255 * this.Opacity);
props.Flags = ThumbnailFlags.Visible |
ThumbnailFlags.SourceClientAreaOnly |
ThumbnailFlags.Opacity;
DwmUtils.DwmUpdateThumbnailProperties(_thumb, ref props);
}
private void InitialiseThumbnail(IntPtr source)
{
if (IntPtr.Zero != thumb)
{
// release the old thumbnail
ReleaseThumbnail();
}
if (IntPtr.Zero != source)
{
// find our parent hwnd
target = (HwndSource)HwndSource.FromVisual(this);
// if we have one, we can attempt to register the thumbnail
if (target != null && 0 == DwmUtils.DwmRegisterThumbnail(target.Handle, source, out this.thumb))
{
DwmThumbnailProperties props = new DwmThumbnailProperties();
props.Visible = false;
props.SourceClientAreaOnly = this.ClientAreaOnly;
props.Opacity = (byte)(255 * this.Opacity);
props.Flags = ThumbnailFlags.Visible | ThumbnailFlags.SourceClientAreaOnly
| ThumbnailFlags.Opacity;
DwmUtils.DwmUpdateThumbnailProperties(thumb, ref props);
}
}
}
// this is where the magic happens
private void Thumbnail_LayoutUpdated(object sender, EventArgs e)
{
if (IntPtr.Zero == thumb)
{
InitialiseThumbnail(this.Source);
}
if (IntPtr.Zero != thumb)
{
if (!target.RootVisual.IsAncestorOf(this))
{
//we are no longer in the visual tree
ReleaseThumbnail();
return;
}
GeneralTransform transform = TransformToAncestor(target.RootVisual);
Point a = transform.Transform(new Point(0, 0));
Point b = transform.Transform(new Point(this.ActualWidth, this.ActualHeight));
DwmThumbnailProperties props = new DwmThumbnailProperties();
props.Visible = true;
props.Destination = new Rect(
(int)Math.Ceiling(a.X), (int)Math.Ceiling(a.Y),
(int)Math.Ceiling(b.X), (int)Math.Ceiling(b.Y));
props.Flags = ThumbnailFlags.Visible | ThumbnailFlags.RectDetination;
DwmUtils.DwmUpdateThumbnailProperties(thumb, ref props);
}
}
public void DrawRectForWindow()
{
if (IntPtr.Zero == _thumb)
{
InitializeThumbnail();
}
if (IntPtr.Zero == _thumb)
{
return;
}
if (!_target.RootVisual.IsAncestorOf(this))
{
//we are no longer in the visual tree
ReleaseThumbnail();
return;
}
double scale = DwmUtils.GetSystemScale();
// keep original window aspect ratio
double windowWidth = WindowRect.Right - WindowRect.Left;
double windowHeight = WindowRect.Bottom - WindowRect.Top;
Point origin = new Point(Canvas.GetLeft(this), Canvas.GetTop(this));
double scaleFactor = Height / windowHeight;
windowHeight = scaleFactor * windowHeight;
windowWidth = scaleFactor * windowWidth;
// origins remain the same as provided
var rect = new Rect(
(int)(origin.X),
(int)(origin.Y),
(int)(origin.X + windowWidth),
(int)(origin.Y + windowHeight));
var scaledRect = new Rect(
(int)(origin.X * scale),
(int)(origin.Y * scale),
(int)((origin.X + windowWidth) * scale),
(int)((origin.Y + windowHeight) * scale));
DwmThumbnailProperties props = new DwmThumbnailProperties();
props.Visible = true;
props.Destination = scaledRect;
// props.Destination = new DWM.Rect(
// (int) Math.Ceiling(a.X), (int) Math.Ceiling(a.Y),
// (int) Math.Ceiling(b.X), (int) Math.Ceiling(b.Y));
props.Flags = ThumbnailFlags.Visible | ThumbnailFlags.RectDetination;
DwmUtils.DwmUpdateThumbnailProperties(_thumb, ref props);
}
private void UpdateThumbnail()
{
if (IntPtr.Zero != thumb)
{
DwmThumbnailProperties props = new DwmThumbnailProperties();
props.SourceClientAreaOnly = this.ClientAreaOnly;
props.Opacity = (byte)(255 * this.Opacity);
props.Flags = ThumbnailFlags.SourceClientAreaOnly | ThumbnailFlags.Opacity;
DwmUtils.DwmUpdateThumbnailProperties(thumb, ref props);
}
}
public static extern int DwmUpdateThumbnailProperties(IntPtr hThumbnail, ref DwmThumbnailProperties props);
