Sets fonts in forms to the first-available font in a list of fonts. Adjusts size of fonts to match a baseline font, so e.g. 9pt Calibri will be the same size as 9pt Verdana.

FontFamilies.cs

// Author: Adam Smith <adam@adamsmith.cc>
// License: public domain

    internal static class FontFamilies {

        static FontFamilies() {
            DefaultAppFontFamily = GetFirstAvailableFontFamily(new string[] { "Segoe UI", "Calibri", "Verdana" });
            Log.Logger.Debug(string.Format("Using font family {0}", DefaultAppFontFamily.Name));

            HeightTargetFontFamily = GetFirstAvailableFontFamily(new string[] { "Verdana" });
        }

        internal static void SetFontFamilyForDescendents(Graphics g, Control control) {
            if (DefaultAppFontFamily == null || HeightTargetFontFamily == null) {
                return;
            }
            
            try {
                foreach (Control child in control.Controls) {
                    if (child is ContainerControl) {
                        // don't change the fonts of container controls
                        // they will often have an AutoScaleMode that will change the size of the control depending on the
                        //   font size.
                    } else {
                        if (DefaultAppFontFamily.IsStyleAvailable(child.Font.Style)) {
                            var newFont = new Font(DefaultAppFontFamily, child.Font.Size, child.Font.Style, child.Font.Unit);

                            // measure difference in font height
                            // some fonts like Calibri are noticible smaller, unfortunately
                            var newFamilyTestSize = MeasureRealFontSize(g, newFont);
                            var oldFamilyTestSize = MeasureRealFontSize(g, child.Font);
                            var sizeRatio = oldFamilyTestSize / newFamilyTestSize;

                            newFont = new Font(newFont.FontFamily, newFont.Size * sizeRatio, newFont.Style, newFont.Unit);

                            child.Font = newFont;
                        }
                    }

                    SetFontFamilyForDescendents(g, child);
                }
            } catch (Exception e) {
                Log.Logger.ErrorException("Error setting font family of control's descendents", e);
            }
        }

        private static FontFamily DefaultAppFontFamily { get; set; }
        private static FontFamily HeightTargetFontFamily { get; set; }

        private static float MeasureRealFontSize(Graphics g, Font font) {
            var testString = "Test String";

            using (var format = new StringFormat()) {
                format.SetMeasurableCharacterRanges(new CharacterRange[] { new CharacterRange(0, testString.Length) });

                using (var region = g.MeasureCharacterRanges(testString, font,
                        new RectangleF(PointF.Empty, new SizeF(1000, 1000)), format)[0]) {

                    var bounds = region.GetBounds(g);
                    return (float)Math.Sqrt(Math.Pow(bounds.Height, 2) + Math.Pow(bounds.Width, 2));
                }
            }
        }

        private static FontFamily GetFirstAvailableFontFamily(string[] fontFamilyStack) {
            foreach (var fontFamily in fontFamilyStack) {
                try {
                    return new FontFamily(fontFamily);
                } catch {
                    Log.Logger.Debug(string.Format("Exception getting {0} font.  Falling back to next default...", fontFamily));
                }
            }
            return FontFamily.GenericSansSerif;
        }
    }