add Transformable instance for FontSize

src/Diagrams/TwoD/Attributes.hs

@@ -2,7 +2,6 @@
 {-# LANGUAGE FlexibleInstances          #-}
 {-# LANGUAGE GeneralizedNewtypeDeriving #-}
 {-# LANGUAGE TypeFamilies               #-}
-{-# OPTIONS_GHC -fno-warn-orphans       #-}
 
 -----------------------------------------------------------------------------
 -- |
@@ -38,15 +37,8 @@ import           Data.Default.Class
 import           Data.Semigroup
 
 import           Diagrams.Core
-import           Diagrams.TwoD.Types (R2)
+import           Diagrams.TwoD.Types
 
------------------------------------------------------------------
-
-type instance V (Measure Double) = R2
-
-instance Transformable (Measure Double) where
-  transform tr (Local x) = Local (avgScale tr * x)
-  transform _ y = y
 
 -----------------------------------------------------------------
 --  Line Width  -------------------------------------------------

src/Diagrams/TwoD/Text.hs

@@ -38,8 +38,8 @@ import           Diagrams.TwoD.Types
 import           Data.AffineSpace       ((.-.))
 import           Data.Semigroup
 import           Data.Colour
+import           Data.Data
 import           Data.Default.Class
-import           Data.Typeable
 
 ------------------------------------------------------------
 -- Text diagrams
@@ -162,25 +162,31 @@ font = applyAttr . Font . Last
 -- | The @FontSize@ attribute specifies the size of a font's
 --   em-square.  Inner @FontSize@ attributes override outer ones.
 newtype FontSize = FontSize (Last (Measure Double))
-  deriving (Typeable, Semigroup)
+  deriving (Typeable, Data, Semigroup)
 instance AttributeClass FontSize
 
+type instance V FontSize = R2
+
 instance Default FontSize where
     def = FontSize (Last (Local 1))
 
+instance Transformable FontSize where
+  transform t (FontSize (Last s)) =
+    FontSize (Last (transform t s))
+
 -- | Extract the size from a @FontSize@ attribute.
 getFontSize :: FontSize -> Measure Double
 getFontSize (FontSize (Last s)) = s
 
 -- | Set the font size, that is, the size of the font's em-square as
 --   measured within the current local vector space.  The default size
 --   is @1@.
-fontSize :: HasStyle a => Measure Double -> a -> a
-fontSize = applyAttr . FontSize . Last
+fontSize :: (HasStyle a, V a ~ R2) => Measure Double -> a -> a
+fontSize = applyGTAttr . FontSize . Last
 
 -- | Apply a 'FontSize' attribute.
-fontSizeA :: HasStyle a => FontSize -> a -> a
-fontSizeA = applyAttr
+fontSizeA :: (HasStyle a, V a ~ R2) => FontSize -> a -> a
+fontSizeA = applyGTAttr
 
 --------------------------------------------------
 -- Font slant

src/Diagrams/TwoD/Types.hs

@@ -244,3 +244,11 @@ instance HasR P2 where
 
 instance HasTheta P2 where
     _theta = _relative origin . _theta
+
+-----------------------------------------------------------------
+
+type instance V (Measure Double) = R2
+
+instance Transformable (Measure Double) where
+  transform tr (Local x) = Local (avgScale tr * x)
+  transform _ y = y