diagrams-cairo-0.6: src/Diagrams/Backend/Cairo/Internal.hs
{-# LANGUAGE TypeFamilies
, MultiParamTypeClasses
, FlexibleInstances
, FlexibleContexts
, ExistentialQuantification
, TypeSynonymInstances
, DeriveDataTypeable
, ViewPatterns
#-}
-----------------------------------------------------------------------------
-- |
-- Module : Diagrams.Backend.Cairo.Internal
-- Copyright : (c) 2011 Diagrams-cairo team (see LICENSE)
-- License : BSD-style (see LICENSE)
-- Maintainer : diagrams-discuss@googlegroups.com
--
-- This module contains the internal implementation guts of the
-- diagrams cairo backend. If you want to see how the cairo backend
-- works under the hood, you are in the right place (try clicking on
-- the \"Source\" links). (Guts under the hood, what an awful mixed
-- metaphor.) If you know what you are doing and really want access
-- to the internals of the implementation, you are also in the right
-- place. Otherwise, you should have no need of this module; import
-- "Diagrams.Backend.Cairo.CmdLine" or "Diagrams.Backend.Cairo"
-- instead.
--
-- The one exception is that this module may have to be imported
-- sometimes to work around an apparent bug in certain versions of
-- GHC, which results in a \"not in scope\" error for 'CairoOptions'.
--
-----------------------------------------------------------------------------
module Diagrams.Backend.Cairo.Internal where
import Diagrams.Core.Transform
import Diagrams.Prelude
import Diagrams.TwoD.Path (Clip(..), getFillRule)
import Diagrams.TwoD.Text
import Diagrams.TwoD.Image
import Diagrams.TwoD.Adjust (adjustDia2D, setDefault2DAttributes)
import Diagrams.TwoD.Size (requiredScaleT)
import qualified Graphics.Rendering.Cairo as C
import qualified Graphics.Rendering.Cairo.Matrix as CM
import Control.Monad.State
import Data.Maybe (catMaybes, fromMaybe)
import Data.List (isSuffixOf)
import Control.Exception (try)
import qualified Data.Foldable as F
import Data.Typeable
-- | This data declaration is simply used as a token to distinguish
-- the cairo backend: (1) when calling functions where the type
-- inference engine would otherwise have know way to know which
-- backend you wanted to use, and (2) as an argument to the
-- 'Backend' and 'Renderable' type classes.
data Cairo = Cairo
deriving (Eq,Ord,Read,Show,Typeable)
-- | Output types supported by cairo, including four different file
-- types (PNG, PS, PDF, SVG). If you want to output directly to GTK
-- windows, see the diagrams-gtk package.
data OutputType =
PNG -- ^ Portable Network Graphics output.
| PS -- ^ PostScript output
| PDF -- ^ Portable Document Format output.
| SVG -- ^ Scalable Vector Graphics output.
| RenderOnly -- ^ Don't output any file; the returned @IO ()@
-- action will do nothing, but the @Render ()@ action
-- can be used (e.g. to draw to a Gtk window)
instance Monoid (Render Cairo R2) where
mempty = C $ return ()
(C rd1) `mappend` (C rd2) = C (rd1 >> rd2)
-- | The custom monad in which intermediate drawing options take
-- place; 'Graphics.Rendering.Cairo.Render' is cairo's own rendering
-- monad. At one point @RenderM@ really did use @StateT@, but then
-- the state got taken out... but the @StateT@ remains, now with a
-- zen-like state of type unit, \"just in case\". Think of it as a
-- good luck charm.
type RenderM a = StateT () C.Render a -- no state for now
-- simple, stupid implementations of save and restore for now, since
-- it suffices to just reset the text alignment to "centered" on
-- restore. But if need be we can switch to a more sophisticated
-- implementation using an "undoable state" monad which lets you save
-- (push state onto a stack) and restore (pop from the stack).
-- | Push the current context onto a stack.
save :: RenderM ()
save = lift C.save
-- | Restore the context from a stack.
restore :: RenderM ()
restore = lift C.restore
instance Backend Cairo R2 where
data Render Cairo R2 = C (RenderM ())
type Result Cairo R2 = (IO (), C.Render ())
data Options Cairo R2 = CairoOptions
{ cairoFileName :: String -- ^ The name of the file you want generated
, cairoSizeSpec :: SizeSpec2D -- ^ The requested size of the output
, cairoOutputType :: OutputType -- ^ the output format and associated options
, cairoBypassAdjust :: Bool -- ^ Should the 'adjustDia' step be bypassed during rendering?
}
withStyle _ s t (C r) = C $ do
save
cairoMiscStyle s
r
lift $ do
cairoTransf t
cairoStrokeStyle s
C.stroke
restore
doRender _ (CairoOptions file size out _) (C r) = (renderIO, r')
where r' = evalStateT r ()
renderIO = do
let surfaceF s = C.renderWith s r'
-- Everything except Dims is arbitrary. The backend
-- should have first run 'adjustDia' to update the
-- final size of the diagram with explicit dimensions,
-- so normally we would only expect to get Dims anyway.
(w,h) = case size of
Width w' -> (w',w')
Height h' -> (h',h')
Dims w' h' -> (w',h')
Absolute -> (100,100)
case out of
PNG ->
C.withImageSurface C.FormatARGB32 (round w) (round h) $ \surface -> do
surfaceF surface
C.surfaceWriteToPNG surface file
PS -> C.withPSSurface file w h surfaceF
PDF -> C.withPDFSurface file w h surfaceF
SVG -> C.withSVGSurface file w h surfaceF
RenderOnly -> return ()
adjustDia c opts d = if cairoBypassAdjust opts
then (opts, d # setDefault2DAttributes)
else adjustDia2D cairoSizeSpec
setCairoSizeSpec
c opts (d # reflectY)
where setCairoSizeSpec sz o = o { cairoSizeSpec = sz }
renderC :: (Renderable a Cairo, V a ~ R2) => a -> RenderM ()
renderC a = case (render Cairo a) of C r -> r
-- | Handle \"miscellaneous\" style attributes (clip, font stuff, fill
-- color and fill rule).
cairoMiscStyle :: Style v -> RenderM ()
cairoMiscStyle s =
sequence_
. catMaybes $ [ handle clip
, handle fSize
, handleFontFace
, handle fColor
, handle lFillRule
]
where handle :: AttributeClass a => (a -> RenderM ()) -> Maybe (RenderM ())
handle f = f `fmap` getAttr s
clip = mapM_ (\p -> renderC p >> lift C.clip) . getClip
fSize = lift . C.setFontSize . getFontSize
fFace = fromMaybe "" $ getFont <$> getAttr s
fSlant = fromFontSlant . fromMaybe FontSlantNormal
$ getFontSlant <$> getAttr s
fWeight = fromFontWeight . fromMaybe FontWeightNormal
$ getFontWeight <$> getAttr s
handleFontFace = Just . lift $ C.selectFontFace fFace fSlant fWeight
fColor c = lift $ setSource (getFillColor c) s
lFillRule = lift . C.setFillRule . fromFillRule . getFillRule
fromFontSlant :: FontSlant -> C.FontSlant
fromFontSlant FontSlantNormal = C.FontSlantNormal
fromFontSlant FontSlantItalic = C.FontSlantItalic
fromFontSlant FontSlantOblique = C.FontSlantOblique
fromFontWeight :: FontWeight -> C.FontWeight
fromFontWeight FontWeightNormal = C.FontWeightNormal
fromFontWeight FontWeightBold = C.FontWeightBold
-- | Handle style attributes having to do with stroke.
cairoStrokeStyle :: Style v -> C.Render ()
cairoStrokeStyle s =
sequence_
. catMaybes $ [ handle fColor
, handle lColor -- see Note [color order]
, handle lWidth
, handle lCap
, handle lJoin
, handle lDashing
]
where handle :: (AttributeClass a) => (a -> C.Render ()) -> Maybe (C.Render ())
handle f = f `fmap` getAttr s
fColor c = setSource (getFillColor c) s >> C.fillPreserve
lColor c = setSource (getLineColor c) s
lWidth = C.setLineWidth . getLineWidth
lCap = C.setLineCap . fromLineCap . getLineCap
lJoin = C.setLineJoin . fromLineJoin . getLineJoin
lDashing (getDashing -> Dashing ds offs) =
C.setDash ds offs
setSource :: Color c => c -> Style v -> C.Render ()
setSource c s = C.setSourceRGBA r g b a'
where (r,g,b,a) = colorToRGBA c
a' = case getOpacity <$> getAttr s of
Nothing -> a
Just d -> a * d
-- | Multiply the current transformation matrix by the given 2D
-- transformation.
cairoTransf :: T2 -> C.Render ()
cairoTransf t = C.transform m
where m = CM.Matrix a1 a2 b1 b2 c1 c2
(unr2 -> (a1,a2)) = apply t unitX
(unr2 -> (b1,b2)) = apply t unitY
(unr2 -> (c1,c2)) = transl t
{- ~~~~ Note [color order]
It's important for the line and fill colors to be handled in the
given order (fill color first, then line color) because of the way
Cairo handles them (both are taken from the sourceRGBA).
-}
fromLineCap :: LineCap -> C.LineCap
fromLineCap LineCapButt = C.LineCapButt
fromLineCap LineCapRound = C.LineCapRound
fromLineCap LineCapSquare = C.LineCapSquare
fromLineJoin :: LineJoin -> C.LineJoin
fromLineJoin LineJoinMiter = C.LineJoinMiter
fromLineJoin LineJoinRound = C.LineJoinRound
fromLineJoin LineJoinBevel = C.LineJoinBevel
fromFillRule :: FillRule -> C.FillRule
fromFillRule Winding = C.FillRuleWinding
fromFillRule EvenOdd = C.FillRuleEvenOdd
instance Renderable (Segment R2) Cairo where
render _ (Linear v) = C . lift $ uncurry C.relLineTo (unr2 v)
render _ (Cubic (unr2 -> (x1,y1))
(unr2 -> (x2,y2))
(unr2 -> (x3,y3)))
= C . lift $ C.relCurveTo x1 y1 x2 y2 x3 y3
instance Renderable (Trail R2) Cairo where
render _ (Trail segs c) = C $ do
mapM_ renderC segs
lift $ when c C.closePath
instance Renderable (Path R2) Cairo where
render _ (Path trs) = C $ lift C.newPath >> F.mapM_ renderTrail trs
where renderTrail (unp2 -> p, tr) = do
lift $ uncurry C.moveTo p
renderC tr
-- Can only do PNG files at the moment...
instance Renderable Image Cairo where
render _ (Image file sz tr) = C . lift $ do
if ".png" `isSuffixOf` file
then do
C.save
cairoTransf (tr <> reflectionY)
pngSurfChk <- liftIO (try $ C.imageSurfaceCreateFromPNG file
:: IO (Either IOError C.Surface))
case pngSurfChk of
Right pngSurf -> do
w <- C.imageSurfaceGetWidth pngSurf
h <- C.imageSurfaceGetHeight pngSurf
cairoTransf $ requiredScaleT sz (fromIntegral w, fromIntegral h)
C.setSourceSurface pngSurf (-fromIntegral w / 2)
(-fromIntegral h / 2)
Left _ ->
liftIO . putStrLn $
"Warning: can't read image file <" ++ file ++ ">"
C.paint
C.restore
else
liftIO . putStr . unlines $
[ "Warning: Cairo backend can currently only render embedded"
, " images in .png format. Ignoring <" ++ file ++ ">."
]
-- see http://www.cairographics.org/tutorial/#L1understandingtext
instance Renderable Text Cairo where
render _ (Text tr al str) = C $ do
lift $ do
C.save
-- XXX should use reflection font matrix here instead?
cairoTransf (tr <> reflectionY)
(refX, refY) <- case al of
BoxAlignedText xt yt -> do
tExt <- C.textExtents str
fExt <- C.fontExtents
let l = C.textExtentsXbearing tExt
r = C.textExtentsXadvance tExt
b = C.fontExtentsDescent fExt
t = C.fontExtentsAscent fExt
return (lerp l r xt, lerp (-b) t yt)
BaselineText -> return (0, 0)
cairoTransf (moveOriginBy (r2 (refX, -refY)) mempty)
C.showText str
C.restore