How Can I Accurately Determine Windows Display Scaling Factor in C#?

Accessing and Utilizing Windows Display Scaling in C# Applications

Windows users can adjust display scaling to modify the size of text and UI elements. This capability is crucial for C# developers who need to adapt their applications to different scaling settings for optimal user experience.

Precisely Determining the Scaling Factor

Standard methods like Graphics.DpiX and DeviceCap.LOGPIXELSX can be unreliable in determining the accurate scaling factor. A more robust approach involves calculating the factor using logical and physical screen heights:

<code class="language-csharp">[DllImport("gdi32.dll")]
static extern int GetDeviceCaps(IntPtr hdc, int nIndex);

public enum DeviceCap
{
    VERTRES = 10,
    DESKTOPVERTRES = 117,
}

private float GetScalingFactor()
{
    using (Graphics g = Graphics.FromHwnd(IntPtr.Zero))
    {
        IntPtr desktop = g.GetHdc();
        int logicalHeight = GetDeviceCaps(desktop, (int)DeviceCap.VERTRES);
        int physicalHeight = GetDeviceCaps(desktop, (int)DeviceCap.DESKTOPVERTRES);
        g.ReleaseHdc(desktop);
        return (float)physicalHeight / logicalHeight;
    }
}</code>

This function leverages GetDeviceCaps to obtain the logical and physical screen heights. The scaling factor is then computed as the ratio of these heights, offering a precise reflection of the user's display scaling settings. This ensures consistent application behavior across various display configurations.

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