How Can I Programmatically Retrieve Windows Display Scaling Settings?

Programmatically determine Windows display settings

In Windows 7 and above, users can adjust display parameters, such as text size, in the Control Panel. Accessing these settings is useful to enable or disable application functionality based on user preference.

Can these display settings be retrieved programmatically?

It turns out that both the graphics.DpiX and DeviceCap.LOGPIXELSX properties return a consistent value of 96 on Surface Pro devices regardless of zoom level. To accurately calculate the scaling factor, another approach is required.

An effective method is to utilize the gdi32.dll function in GetDeviceCaps. By measuring the logical and physical screen height we can determine the screen scaling factor.

<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);

    float ScreenScalingFactor = (float)PhysicalScreenHeight / (float)LogicalScreenHeight;

    return ScreenScalingFactor;
}</code>

By calling this function we can accurately obtain the screen scaling factor, allowing us to adjust application behavior accordingly.

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