如何获得Windows窗体相对于显示器的正确位置？

Question

I have searched for hours and tried many things.

I have a transparent Windows Form and I am trying to capture the screen within the bounds of that form.

For whatever reason, I am unable to get the correct form area...

[DllImport("user32.dll")]
public static extern IntPtr GetDC(IntPtr ptr);

[DllImport("user32.dll")]
public static extern bool ReleaseDC(IntPtr hWnd, IntPtr hDC);

private void LocationChanged(object sender, EventArgs e)
{
    var position = form.PointToScreen(Point.Empty);
    bounds = new Rectangle(position, new Size(50, 50));
    DrawRectangle(bounds);
}

void DrawRectangle(Rectangle rect)
{
    IntPtr desktopPtr = GetDC(IntPtr.Zero);
    Graphics g = Graphics.FromHdc(desktopPtr);

    SolidBrush b = new SolidBrush(Color.Green);
    g.FillRectangle(b, rect);

    g.Dispose();
    ReleaseDC(IntPtr.Zero, desktopPtr);
}

This is the result:

The green square should completely cover the form with the red border on the left.

I've tried different monitors, I've made sure scaling is 100% ( what to do if it is not? ), I'e tried passing the form.Location to form.PointToScreen

What am I doing wrong?

Answer 1

You can try setting the property form.StartPosition = FormPosition.Manual

https://docs.microsoft.com/en-us/dotnet/api/system.windows.forms.form.startposition?view=netframework-4.7.2