Detecting the Display Font Size

Introduction

As you've probably seen, the end-user can specify their Font Size to be "Small Fonts", "Large Fonts" or "Custom Font" via the Control Panel's Display applet (Figure 1 below). Since this setting could adversely affect an application's user interface (UI), there are many times in more advanced applications where the knowledge of which setting has been chosen by the user would be useful. For example, this information can be used in determining which dialog to present (if you wanted to present a tailor-made dialog for each font size). In addition, knowing the currently selected font size could be used to give your application's end-user a warning had the UI been designed with only smaller fonts in mind. Whatever your need, this handly little function will assist you in programmatically determining the selected font size.

Figure 1 - Sometimes the end-user's choice of font size can wreak havoc with a carefully designed UI.

Function to Detect Font Size

The following code demonstrates how to detect it.

CDC ScreenDC;
VERIFY(ScreenDC.CreateIC(_T("DISPLAY"), NULL, NULL, NULL));
const int nLogDPIX = ScreenDC.GetDeviceCaps(LOGPIXELSX),
          nLogDPIY = ScreenDC.GetDeviceCaps(LOGPIXELSY);

if (nLogDPIX == 96 && nLogDPIY == 96)
{
    // 96 DPI, Small Fonts
}
else
{
    if (nLogDPIX == 120 && nLogDPIY == 120)
    {
        // 120 DPI, Large Fonts
    }
    else
    {
        // Otherwise, Custom Font Size
    }
}