Calculated the correct font size for use in WPF.

The font size specified in the FontInfo object is in points. WPF does not use points for font sizes, so the font size was always smaller than it should have been.

Author: reduckted

src/toolkit/Community.VisualStudio.Toolkit.Shared/FontsAndColors/BaseFontAndColorCategory.cs

@@ -246,7 +246,7 @@ int IVsFontAndColorEvents.OnFontChanged(ref Guid rguidCategory, FontInfo[] pInfo
             // only want to handle the changes for this category.
             if (rguidCategory.Equals(_categoryGuid))
             {
-                EmitChange((x) => x.SetFont(ref pInfo[0]));
+                EmitChange((x) => x.SetFont(ref pLOGFONT[0], ref pInfo[0]));
             }
             return VSConstants.S_OK;
         }

src/toolkit/Community.VisualStudio.Toolkit.Shared/FontsAndColors/ConfiguredFont.cs

@@ -1,4 +1,5 @@
-using System.ComponentModel;
+using System;
+using System.ComponentModel;
 using System.Windows.Media;
 using Microsoft.VisualStudio.PlatformUI;
 using Microsoft.VisualStudio.Shell.Interop;
@@ -22,14 +23,16 @@ public class ConfiguredFont : ObservableObject
         private FontFamily? _family;
         private bool _hasFamily;
         private string _familyName;
+        private int _pointSize;
         private double _size;
         private byte _characterSet;
 
-        internal ConfiguredFont(ref FontInfo info)
+        internal ConfiguredFont(ref LOGFONTW logfont, ref FontInfo fontInfo)
         {
-            _familyName = info.bstrFaceName;
-            _size = info.wPointSize;
-            _characterSet = info.iCharSet;
+            _familyName = fontInfo.bstrFaceName;
+            _pointSize = fontInfo.wPointSize;
+            _size = CalculateFontSize(ref logfont);
+            _characterSet = fontInfo.iCharSet;
         }
 
         /// <summary>
@@ -61,7 +64,14 @@ public FontFamily? Family
         public string FamilyName => _familyName;
 
         /// <summary>
-        /// The font size.
+        /// The font size, in points. This is the value specified on the <i>Fonts and Colors</i> options page.
+        /// </summary>
+        public int PointSize => _pointSize;
+
+        /// <summary>
+        /// The font size, for use in WPF. This is the font size that can be used in WPF controls.
+        /// For example, the value can be used directly in the 
+        /// <see cref="System.Windows.Documents.TextElement.FontSize"/> property.
         /// </summary>
         public double Size => _size;
 
@@ -70,17 +80,19 @@ public FontFamily? Family
         /// </summary>
         public byte CharacterSet => _characterSet;
 
-        internal bool Update(ref FontInfo info)
+        internal bool Update(ref LOGFONTW logfont, ref FontInfo info)
         {
             bool changed = false;
             string oldFaceName = _familyName;
+            int oldPointSize = _pointSize;
             double oldSize = _size;
             byte oldCharacterSet = _characterSet;
 
             // Update all of the fields first so that
             // everything is set before we raise the events.
             _familyName = info.bstrFaceName;
-            _size = info.wPointSize;
+            _pointSize = info.wPointSize;
+            _size = CalculateFontSize(ref logfont);
             _characterSet = info.iCharSet;
 
             if (!string.Equals(oldFaceName, _familyName))
@@ -92,6 +104,12 @@ internal bool Update(ref FontInfo info)
                 NotifyPropertyChanged(nameof(FamilyName));
             }
 
+            if (oldPointSize != _pointSize)
+            {
+                changed = true;
+                NotifyPropertyChanged(nameof(PointSize));
+            }
+
             if (oldSize != _size)
             {
                 changed = true;
@@ -106,5 +124,18 @@ internal bool Update(ref FontInfo info)
 
             return changed;
         }
+
+        private static double CalculateFontSize(ref LOGFONTW logfont)
+        {
+            return Math.Abs(logfont.lfHeight) * 96.0 /
+#if VS14
+                // `DpiAwareness` does not exist in VS 14, so default
+                // to 96.0, which is the standard system DPI.
+                96.0
+#else
+                Microsoft.VisualStudio.Utilities.DpiAwareness.SystemDpiY
+#endif
+                ;
+        }
     }
 }

src/toolkit/Community.VisualStudio.Toolkit.Shared/FontsAndColors/ConfiguredFontAndColorSet.cs

@@ -14,13 +14,14 @@ namespace Community.VisualStudio.Toolkit
 
         internal ConfiguredFontAndColorSet(
             T category,
-            ref FontInfo font,
+            ref LOGFONTW logfont,
+            ref FontInfo fontInfo,
             Dictionary<ColorDefinition, ConfiguredColor> colors,
             Action<IFontAndColorChangeListener> onDispose
         )
         {
             Category = category;
-            Font = new ConfiguredFont(ref font);
+            Font = new ConfiguredFont(ref logfont, ref fontInfo);
             _colors = colors;
             _onDispose = onDispose;
         }
@@ -64,9 +65,9 @@ public ConfiguredColor GetColor(ColorDefinition definition)
         /// </summary>
         public event EventHandler<ConfiguredColorChangedEventArgs>? ColorChanged;
 
-        void IFontAndColorChangeListener.SetFont(ref FontInfo info)
+        void IFontAndColorChangeListener.SetFont(ref LOGFONTW logfont, ref FontInfo info)
         {
-            if (Font.Update(ref info))
+            if (Font.Update(ref logfont, ref info))
             {
                 FontChanged?.Invoke(this, EventArgs.Empty);
             }

src/toolkit/Community.VisualStudio.Toolkit.Shared/FontsAndColors/FontsAndColors.cs

@@ -37,10 +37,12 @@ internal FontsAndColors()
                 T category = BaseFontAndColorCategory<T>.Instance;
 
                 FontInfo[] fontInfo = new FontInfo[1];
-                ErrorHandler.ThrowOnFailure(storage.GetFont(null, fontInfo));
+                LOGFONTW[] logfont = new LOGFONTW[1];
+                ErrorHandler.ThrowOnFailure(storage.GetFont(logfont, fontInfo));
 
                 ConfiguredFontAndColorSet<T> set = new(
                     category,
+                    ref logfont[0],
                     ref fontInfo[0],
                     await GetColorsAsync(category, categoryGuid, storage),
                     category.UnregisterChangeListener

src/toolkit/Community.VisualStudio.Toolkit.Shared/FontsAndColors/IFontAndColorChangeListener.cs

@@ -4,7 +4,7 @@ namespace Community.VisualStudio.Toolkit
 {
     internal interface IFontAndColorChangeListener
     {
-        void SetFont(ref FontInfo info);
+        void SetFont(ref LOGFONTW logfont, ref FontInfo info);
 
         void SetColor(ColorDefinition definition, uint background, uint foreground, FontStyle fontStyle);
     }