fix(font): only notify on font change when necessary

Author: JanDeDobbeleer

src/font/install_windows.go

@@ -23,7 +23,6 @@ func install(font *Font, admin bool) error {
 	//  - Copy the file to the fonts directory
 	//  - Add registry entry
 	//  - Call AddFontResourceW to set the font
-	// -  Notify other applications that the fonts have changed
 	fontsDir := filepath.Join(os.Getenv("WINDIR"), "Fonts")
 	if !admin {
 		fontsDir = filepath.Join(os.Getenv("USERPROFILE"), "AppData", "Local", "Microsoft", "Windows", "Fonts")
@@ -32,21 +31,21 @@ func install(font *Font, admin bool) error {
 	// check if the Fonts folder exists, if not, create it
 	if _, err := os.Stat(fontsDir); os.IsNotExist(err) {
 		if err = os.MkdirAll(fontsDir, 0755); err != nil {
-			return fmt.Errorf("Unable to create fonts directory: %s", err.Error())
+			return fmt.Errorf("unable to create fonts directory: %s", err.Error())
 		}
 	}
 
 	fullPath := filepath.Join(fontsDir, font.FileName)
-	// validate if font is already installed, remove it in case it is
+	// validate if the font is already installed, remove it in case it is
 	if _, err := os.Stat(fullPath); err == nil {
 		if err = os.Remove(fullPath); err != nil {
-			return fmt.Errorf("Unable to remove existing font file: %s", err.Error())
+			return fmt.Errorf("unable to remove existing font file: %s", err.Error())
 		}
 	}
 
 	err := os.WriteFile(fullPath, font.Data, 0644)
 	if err != nil {
-		return fmt.Errorf("Unable to write font file: %s", err.Error())
+		return fmt.Errorf("unable to write font file: %s", err.Error())
 	}
 
 	// Add registry entry
@@ -61,34 +60,58 @@ func install(font *Font, admin bool) error {
 	if err != nil {
 		// If this fails, remove the font file as well.
 		if nexterr := os.Remove(fullPath); nexterr != nil {
-			return errors.New("Unable to delete font file after registry key open error")
+			return errors.New("unable to delete font file after registry key open error")
 		}
 
-		return fmt.Errorf("Unable to open registry key: %s", err.Error())
+		return fmt.Errorf("unable to open registry key: %s", err.Error())
 	}
+
 	defer k.Close()
 
-	name := fmt.Sprintf("%v (TrueType)", font.Name)
-	if err = k.SetStringValue(name, regValue); err != nil {
+	fontName := fmt.Sprintf("%v (TrueType)", font.Name)
+	var alreadyInstalled, newFontType bool
+
+	// check if we already had this key set
+	oldFullPath, _, err := k.GetStringValue(fontName)
+	if err == nil {
+		alreadyInstalled = true
+		newFontType = oldFullPath != fullPath
+	}
+
+	// do not call AddFontResourceW if the font was already installed
+	if alreadyInstalled && !newFontType {
+		return nil
+	}
+
+	gdi32 := syscall.NewLazyDLL("gdi32.dll")
+	addFontResourceW := gdi32.NewProc("AddFontResourceW")
+
+	// remove the old font resource in case we have a new font type with the same name
+	if newFontType {
+		fontPtr, err := syscall.UTF16PtrFromString(oldFullPath)
+		if err == nil {
+			removeFontResourceW := gdi32.NewProc("RemoveFontResourceW")
+			_, _, _ = removeFontResourceW.Call(uintptr(unsafe.Pointer(fontPtr)))
+		}
+	}
+
+	if err = k.SetStringValue(fontName, regValue); err != nil {
 		// If this fails, remove the font file as well.
 		if nexterr := os.Remove(fullPath); nexterr != nil {
-			return errors.New("Unable to delete font file after registry key set error")
+			return errors.New("unable to delete font file after registry key set error")
 		}
 
-		return fmt.Errorf("Unable to set registry value: %s", err.Error())
+		return fmt.Errorf("unable to set registry value: %s", err.Error())
 	}
 
-	gdi32 := syscall.NewLazyDLL("gdi32.dll")
-	proc := gdi32.NewProc("AddFontResourceW")
-
 	fontPtr, err := syscall.UTF16PtrFromString(fullPath)
 	if err != nil {
 		return err
 	}
 
-	ret, _, _ := proc.Call(uintptr(unsafe.Pointer(fontPtr)))
+	ret, _, _ := addFontResourceW.Call(uintptr(unsafe.Pointer(fontPtr)))
 	if ret == 0 {
-		return errors.New("Unable to add font resource using AddFontResourceW")
+		return errors.New("unable to add font resource using AddFontResourceW")
 	}
 
 	return nil