WPF 为每个屏幕创建一个 Window，并在每个屏幕上居中

Question

编辑：我解决了。在下面的答案中查看我的修复。

我正在开发一个应用程序，它应该在连接到运行它的计算机的每个屏幕上打开一个小弹出窗口。在单个屏幕上执行非常简单（使用 WindowStartupLocation = CenterScreen），但在多个屏幕上执行却异常困难。

我当前的代码是这样的：

        foreach (var s in Screen.AllScreens) //System.Windows.Forms.Screen
        {
            var b = s.Bounds;
            var w = new PopupWindow();

            var oW = w.Width; //Keep track of original size ...
            var oH = w.Height;

            w.Width = 0; //then set the size to 0, to avoid that the 
            w.Height = 0;//popup shows before it is correctly positioned

            w.Show(); //Now show it, so that we can place it (when I
                      //tried to place it before showing, the window
                      //was always repositioned when Show() was called)

            double dpiX = 1, dpiY = 1;
            var presentationsource = PresentationSource.FromVisual(w);

            if (presentationsource != null)
            {
                dpiX = presentationsource.CompositionTarget.TransformToDevice.M11;
                dpiY = presentationsource.CompositionTarget.TransformToDevice.M22;
            }

            var aW = oW*dpiX; //Calculate the actual size of the window
            var aH = oH*dpiY;

            //***** THIS IS WRONG, SEE ANSWER *****
            w.Left = (b.X + (b.Width / dpiX - aW) / 2); //Place it
            w.Top = (b.Y + (b.Height / dpiY - aH) / 2);
            //*************************************

            w.Width = oW; //And set the size back to the original size
            w.Height = oH;
        }

这似乎只在主屏幕上有效。在其他屏幕上，窗口未正确居中。

我想这是因为我对 WPF 和 DPI 的了解非常有限，而且我可能做错了什么。有人能指出我正确的方向吗？

Answer 1

当然，我在这里发布后设法解决了它。当我试图用 DPI 划分整个位置时，看起来我做错了，这导致我走错了我在上面发布的路径。

放置表单的正确行应该是这样的（所有其他代码都可以）：

                w.Left = (b.X + (b.Width - aW) / 2) / dpiX;
                w.Top = (b.Y + (b.Height - aH) / 2) / dpiX;

但是，我仍然认为这是一个简单任务的大量代码，所以如果有人有更好的想法，请告诉我！

所以这是我现在使用的（工作）代码：

    foreach (var s in Screen.AllScreens) //System.Windows.Forms.Screen
    {
        var b = s.Bounds;
        var w = new PopupWindow();

        var oW = w.Width; //Keep track of original size ...
        var oH = w.Height;

        w.Width = 0; //then set the size to 0, to avoid that the 
        w.Height = 0;//popup shows before it is correctly positioned

        w.Show(); //Now show it, so that we can place it (when I
                  //tried to place it before showing, the window
                  //was always repositioned when Show() was called)

        double dpiX = 1, dpiY = 1;
        var ps = PresentationSource.FromVisual(w);
        if (ps != null)
        {
            dpiX = ps.CompositionTarget.TransformToDevice.M11;
            dpiY = ps.CompositionTarget.TransformToDevice.M22;
        }

        var aW = oW*dpiX; //Calculate the actual size of the window
        var aH = oH*dpiY;

        w.Left = (b.X + (b.Width - aW) / 2) / dpiX;
        w.Top = (b.Y + (b.Height - aH) / 2) / dpiX;

        w.Width = oW; //And set the size back to the original size
        w.Height = oH;
    }

Answer 2

        var centers =
            System.Windows.Forms.Screen.AllScreens.Select(
                s =>
                    new
                    {
                        Left = s.Bounds.X + (s.WorkingArea.Right - s.WorkingArea.Left)/2,
                        Top = s.Bounds.Y + (s.WorkingArea.Bottom - s.WorkingArea.Top)/2
                    });

        foreach (var c in centers)
        {
            var w = new Window1();

            w.Left = c.Left - w.Width/2;
            w.Top = c.Top - w.Height/2;

            w.Show();
        }