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Improve DPI-awareness of visual feedback #5

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14415cd
Add dpi-aware mouse location transformation
Fastdeath Jun 25, 2018
833f5ae
Add dpi-aware rendered bitmap resolution
Fastdeath Jun 25, 2018
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63 changes: 45 additions & 18 deletions Source/NDragDrop/DraggableVisualFeedback.xaml.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,13 +11,18 @@

namespace NDragDrop
{
public partial class DraggableVisualFeedback
public partial class DraggableVisualFeedback : Window
{
private const int GwlExstyle = -20;
private const int WsExTransparent = 0x00000020;

private readonly ISystemMouse _systemMouse;
private readonly System.Windows.Point _grabPosition;
private readonly Rect _bounds;
private readonly DrawingVisual _drawingVisual;

private Matrix _fromScreenTransform = Matrix.Identity;
private Matrix _toScreenTransform = Matrix.Identity;

public DraggableVisualFeedback()
{
Expand All @@ -31,22 +36,13 @@ public DraggableVisualFeedback(UIElement uiElement)
: this()
{
_grabPosition = Mouse.GetPosition(uiElement);

var bounds = VisualTreeHelper.GetDescendantBounds(uiElement);
var renderTargetBitmap = new RenderTargetBitmap((int)bounds.Width, (int)bounds.Height, 96, 96, PixelFormats.Pbgra32);

var drawingVisual = new DrawingVisual();
using (var drawingContext = drawingVisual.RenderOpen())
_bounds = VisualTreeHelper.GetDescendantBounds(uiElement);
_drawingVisual = new DrawingVisual();
using (var drawingContext = _drawingVisual.RenderOpen())
{
var visualBrush = new VisualBrush(uiElement);
drawingContext.DrawRectangle(visualBrush, null, new Rect(new System.Windows.Point(), bounds.Size));
drawingContext.DrawRectangle(visualBrush, null, new Rect(new System.Windows.Point(), _bounds.Size));
}

renderTargetBitmap.Render(drawingVisual);

MaxWidth = renderTargetBitmap.PixelWidth;
MaxHeight = renderTargetBitmap.PixelHeight;
TheImage.Source = renderTargetBitmap;
}

[DllImport("Kernel32")]
Expand Down Expand Up @@ -76,29 +72,60 @@ private static IntPtr SetWindowLong(IntPtr hWnd, int nIndex, IntPtr dwNewLong)

private void OnSourceInitialized(object sender, EventArgs eventArgs)
{
InitDeviceTransforms();
RenderBitmap();

var hWnd = new WindowInteropHelper(this).Handle;

var windowLongPtr = GetWindowLong(hWnd, GwlExstyle);
if (windowLongPtr == IntPtr.Zero) return;

windowLongPtr = (IntPtr.Size == 4)
? (IntPtr) (windowLongPtr.ToInt32() | WsExTransparent)
: (IntPtr) (windowLongPtr.ToInt64() | WsExTransparent);
? (IntPtr)(windowLongPtr.ToInt32() | WsExTransparent)
: (IntPtr)(windowLongPtr.ToInt64() | WsExTransparent);

SetLastError(0);

SetWindowLong(hWnd, GwlExstyle, windowLongPtr);
}

private void InitDeviceTransforms()
{
PresentationSource source = PresentationSource.FromVisual(this);
if (source == null) return;
if (source.CompositionTarget == null) return;

_fromScreenTransform = source.CompositionTarget.TransformFromDevice;
_toScreenTransform = source.CompositionTarget.TransformToDevice;
}

private void RenderBitmap()
{
var resolution = new Vector(96.0, 96.0) * _toScreenTransform;
var pixelSize = new Vector(_bounds.Width, _bounds.Height) * _toScreenTransform;

var renderTargetBitmap = new RenderTargetBitmap(
(int)pixelSize.X, (int)pixelSize.Y,
resolution.X, resolution.Y, PixelFormats.Pbgra32);
renderTargetBitmap.Render(_drawingVisual);

MaxWidth = _bounds.Width;
MaxHeight = _bounds.Height;
TheImage.Source = renderTargetBitmap;
}

private void MousePositionChanged(object sender, MousePositionChangedEventArgs eventargs)
{
Dispatcher.BeginInvoke(new Action<Point>(UpdateLocation), eventargs.Position);
}

private void UpdateLocation(Point location)
{
Left = location.X -_grabPosition.X;
Top = location.Y - _grabPosition.Y;
Vector locationVec = new Vector(location.X, location.Y);
Vector transformedLocation = locationVec * _fromScreenTransform;

Left = transformedLocation.X - _grabPosition.X;
Top = transformedLocation.Y - _grabPosition.Y;
}
}
}