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

Precisely Retrieving Windows Display Scaling in C# Applications

Adapting application behavior to match user-defined display settings, such as text and element sizing, is a frequent programming task. This article presents a robust C# method for accurately retrieving these settings.

While Graphics.DpiX or DeviceCap.LOGPIXELSX are traditional approaches, they may yield inaccurate scaling values, particularly on high-DPI displays.

A more reliable method involves leveraging the Windows API function GetDeviceCaps to calculate the scaling factor. This function retrieves both logical and physical screen heights, allowing for a precise calculation.

Here's the improved C# code:

<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 logicalScreenHeight = GetDeviceCaps(desktop, (int)DeviceCap.VERTRES);
        int physicalScreenHeight = GetDeviceCaps(desktop, (int)DeviceCap.DESKTOPVERTRES);
        g.ReleaseHdc(desktop);
        return (float)physicalScreenHeight / logicalScreenHeight; // e.g., 1.25 = 125%
    }
}</code>

This refined approach offers superior accuracy in determining the scaling factor across various display scaling levels, enabling more precise adjustments to application functionality based on the user's display configuration.

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