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Breaking change: Top-level forms scale to DPI
Learn about the breaking change in .NET 8 for Windows Forms where top-level forms scale their minimum and maximum size values according to the DPI of the monitor.
01/19/2023

Top-level forms scale minimum and maximum size to DPI

Top-level forms in Windows Forms now scale their xref:System.Windows.Forms.Form.MinimumSize and xref:System.Windows.Forms.Form.MaximumSize values according to the dots per inch (DPI) of the monitor when running in xref:System.Windows.Forms.HighDpiMode.PerMonitorV2?displayProperty=nameWithType mode.

Version introduced

.NET 8 Preview 1

Previous behavior

In .NET 8, the xref:System.Windows.Forms.Form.MinimumSize and xref:System.Windows.Forms.Form.MaximumSize values for top-level forms remained constant regardless of the application DPI mode and the DPI of the monitor where the form is rendered. This sometimes resulted in scaling limitations of the top-level form.

You can also opt into this behavior in .NET 7. To opt in, set the System.Windows.Forms.ScaleTopLevelFormMinMaxSizeForDpi runtime configuration option described in the Recommended action section.

New behavior

Starting in .NET 8, top-level forms scale their xref:System.Windows.Forms.Form.MinimumSize and xref:System.Windows.Forms.Form.MaximumSize values according to the DPI of the monitor when running in xref:System.Windows.Forms.HighDpiMode.PerMonitorV2?displayProperty=nameWithType mode. The behavior of your app might change in the following ways:

  • Run-time dependencies might be impacted when the minimum and maximum size of the form change.
  • New xref:System.Windows.Forms.Form.MinimumSizeChanged and xref:System.Windows.Forms.Form.MaximumSizeChanged events might be raised.
  • The scaled form size now has new constraint values for the minimum and maximum sizes.

Change category

This change is a behavioral change.

Reason for change

This change is part of a broader effort to improve the Windows Forms user experience on high DPI monitors. It enables developers to set minimum and maximum sizes for top-Level forms without having to take the DPI of the monitor into account.

Recommended action

If the new behavior is problematic for you, you can opt out by setting System.Windows.Forms.ScaleTopLevelFormMinMaxSizeForDpi to false in your runtimeconfig.json file.

runtimeconfig.template.json template file:

{
   "configProperties": {
      "System.Windows.Forms.ScaleTopLevelFormMinMaxSizeForDpi": false
   }
}

[appname].runtimeconfig.json output file:

{
   "runtimeOptions": {
      "configProperties": {
         "System.Windows.Forms.ScaleTopLevelFormMinMaxSizeForDpi": false
      }
   }
}

Affected APIs

N/A

See also