For Visual Studio 2022, the answer by SENya only works partially or "sometimes": Changing the VS theme will not properly change the colors immediately like 10% of the time. Also, changing the theme from dark to light will quite often appear to work, but after restarting Visual Studio the dark instead of the light colors get used quite often (more than half the time). All of this is non-deterministic.
After some debugging, I understood the problem as follows: Calling IVsFontAndColorCacheManager.ClearCache() deletes the registry key
"Software\Microsoft\VisualStudio\17.0_4d51a943Exp\FontAndColors\Cache\{75A05685-00A8-4DED-BAE5-E7A50BFA929A}\ItemAndFontInfo"
which is the cache of the font and colors. After the custom theme-change function finishes, some other Visual Studio component
sometimes (but not always) immediately updates the font and color cache. I.e. it calls something like fontAndColorStorage.OpenCategory(ref mFontAndColorCategoryGUID, (uint)__FCSTORAGEFLAGS.FCSF_READONLY | (uint)__FCSTORAGEFLAGS.FCSF_LOADDEFAULTS).
Note the FCSF_LOADDEFAULTS. This causes Visual Studio to re-create the registry key. However, apparently it does not use the colors from the updated IClassificationFormatMap, but instead the colors set on the ClassificationFormatDefinition itself,
which were not updated. Thus, changing the theme, changes the displayed colors immediately (because the IClassificationFormatMap got updated), but the registry cache ends up with the wrong colors. After a restart of VS, it uses the cached values and therefore ends up with the wrong colors.
By changing the colors also on the ClassificationFormatDefinition instances, the issue appears to be fixed.
Details
In my VSDoxyHighlighter (Github) I adapted the answer by SENya as follows:
First, some helper class to store the default text format:
public class TextProperties
{
public readonly Color? Foreground;
public readonly Color? Background;
public readonly bool IsBold;
public readonly bool IsItalic;
public TextProperties(Color? foreground, Color? background, bool isBold, bool isItalic)
{
Foreground = foreground;
Background = background;
IsBold = isBold;
IsItalic = isItalic;
}
}
Then the main class handling the theme stuff, called DefaultColors:
/// <summary>
/// Manages the default colors and formatting of our classifications, suitable for the current Visual Studio's color theme.
/// Thus, it provides access to the default formatting for the current theme, and also updates them if the theme
/// of Visual Studio is changed by the user.
///
/// Note that the user settings are stored per theme in the registry.
///
/// An instance should be created via MEF.
/// </summary>
[Export]
public class DefaultColors : IDisposable
{
DefaultColors()
{
VSColorTheme.ThemeChanged += VSThemeChanged;
mCurrentTheme = GetCurrentTheme();
}
public void Dispose()
{
if (mDisposed) {
return;
}
mDisposed = true;
VSColorTheme.ThemeChanged -= VSThemeChanged;
}
/// <summary>
/// Returns the default colors for our extension's classifications, as suitable for the current color theme.
/// </summary>
public Dictionary<string, TextProperties> GetDefaultFormattingForCurrentTheme()
{
return GetDefaultFormattingForTheme(mCurrentTheme);
}
public void RegisterFormatDefinition(IFormatDefinition f)
{
mFormatDefinitions.Add(f);
}
private enum Theme
{
Light,
Dark
}
static private Dictionary<string, TextProperties> GetDefaultFormattingForTheme(Theme theme)
{
switch (theme) {
case Theme.Light:
return cLightColors;
case Theme.Dark:
return cDarkColors;
default:
throw new System.Exception("Unknown Theme");
}
}
// Event called by Visual Studio multiple times (!) when the user changes the color theme of Visual Studio.
private void VSThemeChanged(ThemeChangedEventArgs e)
{
ThreadHelper.ThrowIfNotOnUIThread();
var newTheme = GetCurrentTheme();
if (newTheme != mCurrentTheme) {
mCurrentTheme = newTheme; // Important: We indirectly access mCurrentTheme during the update, so set it before.
ThemeChangedImpl();
}
}
// Called when the Visual Studio theme changes. Responsible for switching out the default colors
// of the classifications.
//
// Based on:
// - https://stackoverflow.com/a/48993958/3740047
// - https://github.com/dotnet/fsharp/blob/main/vsintegration/src/FSharp.Editor/Classification/ClassificationDefinitions.fs#L133
// - https://github.com/fsprojects-archive/zzarchive-VisualFSharpPowerTools/blob/master/src/FSharpVSPowerTools/Commands/SymbolClassifiersProvider.cs
private void ThemeChangedImpl()
{
ThreadHelper.ThrowIfNotOnUIThread();
var fontAndColorStorage = ServiceProvider.GlobalProvider.GetService<SVsFontAndColorStorage, IVsFontAndColorStorage>();
var fontAndColorCacheManager = ServiceProvider.GlobalProvider.GetService<SVsFontAndColorCacheManager, IVsFontAndColorCacheManager>();
fontAndColorCacheManager.CheckCache(ref mFontAndColorCategoryGUID, out int _);
if (fontAndColorStorage.OpenCategory(ref mFontAndColorCategoryGUID, (uint)__FCSTORAGEFLAGS.FCSF_READONLY) != VSConstants.S_OK) {
throw new System.Exception("Failed to open font and color registry.");
}
IClassificationFormatMap formatMap = mClassificationFormatMapService.GetClassificationFormatMap(category: "text");
try {
formatMap.BeginBatchUpdate();
ColorableItemInfo[] colorInfo = new ColorableItemInfo[1];
foreach (var p in GetDefaultFormattingForTheme(mCurrentTheme)) {
string classificationTypeId = p.Key;
TextProperties newColor = p.Value;
if (fontAndColorStorage.GetItem(classificationTypeId, colorInfo) != VSConstants.S_OK) { //comment from F# repo: "we don't touch the changes made by the user"
IClassificationType classificationType = mClassificationTypeRegistryService.GetClassificationType(classificationTypeId);
var oldProp = formatMap.GetTextProperties(classificationType);
var oldTypeface = oldProp.Typeface;
var foregroundBrush = newColor.Foreground == null ? null : new SolidColorBrush(newColor.Foreground.Value);
var backgroundBrush = newColor.Background == null ? null : new SolidColorBrush(newColor.Background.Value);
var newFontStyle = newColor.IsItalic ? FontStyles.Italic : FontStyles.Normal;
var newWeight = newColor.IsBold ? FontWeights.Bold : FontWeights.Normal;
var newTypeface = new Typeface(oldTypeface.FontFamily, newFontStyle, newWeight, oldTypeface.Stretch);
var newProp = TextFormattingRunProperties.CreateTextFormattingRunProperties(
foregroundBrush, backgroundBrush, newTypeface, null, null,
oldProp.TextDecorations, oldProp.TextEffects, oldProp.CultureInfo);
formatMap.SetTextProperties(classificationType, newProp);
}
}
// Also update all of our ClassificationFormatDefinition values with the new values.
// Without this, changing the theme does not reliably update the colors: Sometimes after restarting VS, we get
// the wrong colors. For example, when switching from the dark to the light theme, we often end up with the colors
// of the dark theme after a VS restart.
// From what I could understand: The call fontAndColorCacheManager.ClearCache() below deletes the registry key
// "Software\Microsoft\VisualStudio\17.0_4d51a943Exp\FontAndColors\Cache\{75A05685-00A8-4DED-BAE5-E7A50BFA929A}\ItemAndFontInfo"
// which is the cache of the font and colors. After our function here finishes, some Visual Studio component
// sometimes (but not always) immediately updates the font and color cache. I.e. it calls something like
// fontAndColorStorage.OpenCategory(ref mFontAndColorCategoryGUID, (uint)__FCSTORAGEFLAGS.FCSF_READONLY | (uint)__FCSTORAGEFLAGS.FCSF_LOADDEFAULTS).
// Note the "FCSF_LOADDEFAULTS". This causes Visual Studio to re-create the registry key. However, apparently
// it does not use the colors from the updated formatMap, but instead the colors set on the ClassificationFormatDefinition,
// which were not yet updated so far. Thus, changing the theme, changes the displayed colors immediately (because we update
// the formatMap), but the registry cache ends up with the wrong colors. After a restart of VS, it uses the cached values
// and therefore we get the wrong colors.
// By changing the colors also on the ClassificationFormatDefinition, the issue appears to be fixed.
foreach (IFormatDefinition f in mFormatDefinitions) {
f.Reinitialize();
}
}
finally {
formatMap.EndBatchUpdate();
fontAndColorStorage.CloseCategory();
if (fontAndColorCacheManager.ClearCache(ref mFontAndColorCategoryGUID) != VSConstants.S_OK) {
throw new System.Exception("Failed to clear cache of FontAndColorCacheManager.");
}
}
}
private Theme GetCurrentTheme()
{
// We need to figure out if our extension should choose the default colors suitable for light or dark themes.
// In principle we could explicitly retrieve the color theme currently active in Visual Studio. However, that
// approach is fundamentally flawed: We could check if the theme is one of the default ones (dark, light, blue,
// etc.), but Visual Studio supports installing additional themes. It is impossible to know all themes existing
// out there. So, what we really want is to check if the dark or the light defaults are more suitable given the
// text editor's background color.
// However, the EnvironmentColors does not seem to contain an element for the text editor's background. So we
// simply use the tool windows' background, as suggested also here: https://stackoverflow.com/a/48993958/3740047
// The simplistic heuristic of just checking the blue color seems to work reasonably well. The magic threshold
// was chosen to (hopefully) select the better value for the themes shown at https://devblogs.microsoft.com/visualstudio/custom-themes/
var referenceColor = VSColorTheme.GetThemedColor(EnvironmentColors.ToolWindowBackgroundColorKey);
return (referenceColor != null && referenceColor.B < 100) ? Theme.Dark : Theme.Light;
}
// Default colors for light color themes.
static readonly Dictionary<string, TextProperties> cLightColors = new Dictionary<string, TextProperties> {
{ IDs.ID_command, new TextProperties(foreground: Color.FromRgb(0, 75, 0), background: null, isBold: true, isItalic: false) },
{ IDs.ID_parameter1, new TextProperties(foreground: Color.FromRgb(0, 80, 218), background: null, isBold: true, isItalic: false) },
// ... further custom classifications
};
// Default colors for dark color themes.
static readonly Dictionary<string, TextProperties> cDarkColors = new Dictionary<string, TextProperties> {
{ IDs.ID_command, new TextProperties(foreground: Color.FromRgb(140, 203, 128), background: null, isBold: true, isItalic: false) },
{ IDs.ID_parameter1, new TextProperties(foreground: Color.FromRgb(86, 156, 214), background: null, isBold: true, isItalic: false) },
// ... further custom classifications
};
private Theme mCurrentTheme;
// GUID of the category in which our classification items are placed (i.e. of the elements in the
// fonts and colors settings of Visual Studio). Not just ours but all sorts of other items exist
// in this category, too.
// Can be found by installing our extension, modifying some of the colors of the classifications in
// the Visual Studio's settings dialog, then exporting the settings and checking the resulting file.
// The section about the modified entries contains the proper GUID.
private const string cFontAndColorCategory = "75A05685-00A8-4DED-BAE5-E7A50BFA929A";
Guid mFontAndColorCategoryGUID = new Guid(cFontAndColorCategory);
[Import]
private IClassificationFormatMapService mClassificationFormatMapService = null;
[Import]
private IClassificationTypeRegistryService mClassificationTypeRegistryService = null;
private List<IFormatDefinition> mFormatDefinitions = new List<IFormatDefinition>();
private bool mDisposed = false;
}
A few points to notice here:
- An instance of
DefaultColors should not be created by hand, but rather only a single instance should get created by MEF (e.g. via an Import attribute). See below.
- The current VS theme is identified by checking some currently active background color, as in this answer. It is in principle possible to check whether the light, blue, blue (high contrast), dark, etc. VS themes are active. However, since the user can install additional themes, the list is endless. Thus, simply checking the background color is more generic and robust.
- The
ClassificationFormatDefinition definitions (which represent the text format used by Visual Studio for the various classifications) are expected to register themselves on the DefaultColors instance via RegisterFormatDefinition().
- To get notified about a theme change of Visual Studio, we subscribe to
VSColorTheme.ThemeChanged. Also note that the event gets fired multiple times per theme change. Since it unnecessary to execute all the update code in ThemeChangedImpl() multiple times, we check whether the new and old themes are different.
- The reaction to the theme change is in
ThemeChangedImpl(). This is the code that is mainly based on the answer by SENya, but with the addition that the ClassificationFormatDefinitions registered previously via RegisterFormatDefinition() get a call to Reinitialize().
For completeness sake, ID_command and ID_parameter1 are some self defined identifiers that are used to identify the ClassificationFormatDefinitions (see below):
/// <summary>
/// Identifiers for the classifications. E.g., Visual Studio will use these strings as keys
/// to store the classification's configuration in the registry.
/// </summary>
public static class IDs
{
public const string ID_command = "VSDoxyHighlighter_Command";
public const string ID_parameter1 = "VSDoxyHighlighter_Parameter1";
// ... further IDs for further classifications
}
Now, the actual ClassificationFormatDefinitions are defined like this:
They inherit from an interface IFormatDefinition (which can be passed to the DefaultColors.RegisterFormatDefinition() function)
public interface IFormatDefinition
{
void Reinitialize();
}
All ClassificationFormatDefinitions are mostly the same: They set the text properties (color, bold, italic, etc) that are appropriate for the current color theme upon construction. This is done by querying the DefaultColors.GetDefaultFormattingForCurrentTheme() function. Moreover, they register themselves on the DefaultColors and implement the Reinitialize() method (which is called by DefaultColors). Since it is always the same, I define a base class FormatDefinitionBase for them:
internal abstract class FormatDefinitionBase : ClassificationFormatDefinition, IFormatDefinition
{
protected FormatDefinitionBase(DefaultColors defaultColors, string ID, string displayName)
{
if (defaultColors == null) {
throw new System.ArgumentNullException("VSDoxyHighlighter: The 'DefaultColors' to a FormatDefinition is null");
}
mID = ID;
mDefaultColors = defaultColors;
mDefaultColors.RegisterFormatDefinition(this);
DisplayName = displayName;
Reinitialize();
}
public virtual void Reinitialize()
{
TextProperties color = mDefaultColors.GetDefaultFormattingForCurrentTheme()[mID];
ForegroundColor = color.Foreground;
BackgroundColor = color.Background;
IsBold = color.IsBold;
IsItalic = color.IsItalic;
}
protected readonly DefaultColors mDefaultColors;
protected readonly string mID;
}
Finally, the actual definitions look like this:
[Export(typeof(EditorFormatDefinition))]
[ClassificationType(ClassificationTypeNames = IDs.ID_command)]
[Name(IDs.ID_command)]
[UserVisible(true)]
[Order(After = /*Whatever is appropriate for your extension*/)]
internal sealed class CommandFormat : FormatDefinitionBase
{
[ImportingConstructor]
public CommandFormat(DefaultColors defaultColors)
: base(defaultColors, IDs.ID_command, "VSDoxyHighlighter - Command")
{
}
}
[Export(typeof(EditorFormatDefinition))]
[ClassificationType(ClassificationTypeNames = IDs.ID_parameter1)]
[Name(IDs.ID_parameter1)]
[UserVisible(true)]
[Order(After = /*Whatever is appropriate for your extension*/)]
internal sealed class ParameterFormat1 : FormatDefinitionBase
{
[ImportingConstructor]
public ParameterFormat1(DefaultColors defaultColors)
: base(defaultColors, IDs.ID_parameter1, "VSDoxyHighlighter - Parameter 1")
{
}
}
//... Further format definitions
Notice that the constructor is marked as ImportingConstructor, so that MEF automatically create a single instance of the DefaultColors class and passes it to the constructors.
So, to summarize:
- The
ClassificationFormatDefinition gets created by MEF. At the same time, MEF also creates an instance of DefaultColors and passes it to the ClassificationFormatDefinition. The ClassificationFormatDefinition sets the default colors and provides a function to allow it to get reinitialized upon theme change. To make this possible, it also registers itself on the DefaultColors instance.
DefaultColors figures out the current theme and contains the default colors for each theme.DefaultColors listens for the VSColorTheme.ThemeChanged event, and if fired, clears the Visual Studio's font and color cache, updates the current classification format map (to display the new colors) and also updates all custom ClassificationFormatDefinition instances with the new colors (so that upon recreation of the font and color cache by VS the correct colors are used for the cache).
