在WPF中将窗口位置设置为跟随光标的问题

Question

I'm attempting to perform a drag and drop operation in WPF. I distinctly remember the days when I did this sort of thing regularly.

I'm using ap/invoke of GetCursorPos() to return screen coordinates. This number is offset from the cursor by quite a bit.

I assumed the issue was scaling due to my laptop's high-DPI setting (120) so I used the following code (stolen from this answer):

private Point ConvertPixelsToUnits(int x, int y)
{
// get the system DPI
IntPtr dDC = GetDC(IntPtr.Zero); // Get desktop DC
int dpi = GetDeviceCaps(dDC, 88);
bool rv = ReleaseDC(IntPtr.Zero, dDC);

// WPF's physical unit size is calculated by taking the 
// "Device-Independant Unit Size" (always 1/96)
// and scaling it by the system DPI
double physicalUnitSize = (1d / 96d) * (double)dpi;
Point wpfUnits = new Point(physicalUnitSize * (double)x,
    physicalUnitSize * (double)y);

return wpfUnits;          
}

While the dpi value is correct from the p/invokes,, the result is way, way off (significantly worse than using the raw GetCursorPos() value).

So after lots of playing around with all the different options I can find, I am at a loss as to how to get the correct values on the Window.

Answer 1

I can make it work with the following, but I'm hoping someone can provide a good explanation:

var transform = PresentationSource.FromVisual(PacksApp.Current.MainWindow).CompositionTarget.TransformFromDevice;
var pointOfMouse = transform.Transform(GetCursorPos());