3rdpartylibs/fastreports.wpf/FastReport.Forms.WPF/Utils/DpiRescaler.cs

using System.Collections.Generic;
using System.Windows.Input;

namespace System.Windows.Forms
{
    public static class DpiRescaler
    {
        public static void Install(Window window, Control control, System.Windows.UIElement wpfControl, EventHandler handler)
        {
            if (window == null)
                return;
            window.DpiChanged += (sender, e) =>
            {
                // this event is fired when current dpi is changed:
                // - when you move a window to another monitor with different dpi;
                // - when you change dpi while window is open;
                // - when you have changed dpi while app is running and you open a new window;
                // - if you moved an app to another monitor and open a new window.

                // For the two latter cases, window is created using the default dpi (default monitor dpi).
                // When a window is about to show, WPF scales its controls and fires DpiChanged event.
                // We need some more work to make docking/anchor system behave correctly on rescale.

                // we need only event coming from the window
                if (e.Source == window)
                {
                    var controls = new List<Control>();
                    // suspend layout of all form controls before proceed. 
                    EnumControls(control, c => 
                    { 
                        c.BeforeDpiChange();
                        // collect processed controls
                        controls.Add(c);
                    });
                    // hide the root form control to avoid weird visual effects (partially rendered controls during dpi change)
                    wpfControl.Visibility = Visibility.Hidden;
                    // this action will be performed after the form is rescaled completely. Async is required
                    window.Dispatcher.InvokeAsync(() =>
                    {
                        // original code was:
                        // float rescale = DeviceDpi / AutoScaleDimensions.Width;
                        // we need to check this case (bug: FR dialog form designer does not scale properly)
                        float rescale = control is ContainerControl container ?
                            container.DeviceDpi / container.AutoScaleDimensions.Width :
                            (float)(e.NewDpi.PixelsPerInchX / e.OldDpi.PixelsPerInchX);
                        // process controls in reverse order to match Suspend/Resume calls (important, case: StdReportWizard bad rescale on pmV2)
                        controls.Reverse();
                        controls.ForEach(c => c.AfterDpiChange(rescale));
                        handler(control, e);

                        // restore the root control visibility, do it cool
                        wpfControl.Visibility = Visibility.Visible;
                        wpfControl.AnimateOpacity(0, 1, 100);

                        // hiding/showing the container causes focus lost. Restore the focus (issue with FR text editor showing on non-primary monitor)
                        FocusManager.GetFocusedElement(window)?.Focus();
                    });
                    
                    void EnumControls(Control control, Action<Control> action)
                    {
                        action(control);
                        foreach (Control c in control.Controls)
                            EnumControls(c, action);
                    }
                }
            };
        }
    }
}