Unusual scaling for some Windows Forms applications with the .NET Framework 4.5.2

Symptoms

Windows Forms applications that implement their own scaling logic for high DPI settings may encounter unusual scaling if these applications are opted into the Microsoft .NET Framework 4.5.2 High DPI changes by using the following .config file setting:

<appSettings>

 <add key="EnableWindowsFormsHighDpiAutoResizing" value="true" />

</appSettings>

Resolution

Applications that apply a scaling factor on top of the scaled value will encounter extra scaling when they are opted into the .NET Framework 4.5.2 High DPI improvements. To resolve this issue, update the application’s scaling logic to apply scaling on the ToolStrip.ImageScalingSize default value. This change will avoid the introduction of extra scaling. 

For example, applications that have the following code will scale ToolStrip buttons twice:

public MyToolStrip()

{

 IntPtr hDC = GetDC(new HandleRef(null, IntPtr.Zero));

 double xFactor = GetDeviceCaps(new HandleRef(null, hDC), LOGPIXELSX) / 96.0;

 double yFactor = GetDeviceCaps(new HandleRef(null, hDC), LOGPIXELSY) / 96.0;

 this.ImageScalingSize = new Size((int)(this.ImageScalingSize.Width * xFactor), (int)(this.ImageScalingSize.Height * yFactor));

 InitializeComponent();

}

You can use the following code to scale from the constant default size, or from your desired image size:

this.ImageScalingSize = new Size((int)(16 * xFactor), (int)(16 * yFactor));