$ cabal install diagrams-gtk
Resolving dependencies...
Notice: installing into a sandbox located at
/home/sk/prg/diagrams/.cabal-sandbox
Configuring cairo-0.13.3.0...
Configuring glib-0.13.4.0...
Failed to install cairo-0.13.3.0
Build log ( /home/sk/prg/diagrams/.cabal-sandbox/logs/cairo-0.13.3.0.log ):
Failed to install glib-0.13.4.0
Build log ( /home/sk/prg/diagrams/.cabal-sandbox/logs/glib-0.13.4.0.log ):
cabal: Error: some packages failed to install:
cairo-0.13.3.0 failed during the configure step. The exception was:
user error ('/usr/bin/ghc' exited with an error:

/tmp/cabal-tmp-18504/cairo-0.13.3.0/dist/dist-sandbox-df16c69b/setup/setup.hs:5:8:
Could not find module ‘Gtk2HsSetup’
Use -v to see a list of the files searched for.
)
diagrams-cairo-1.3.0.6 depends on glib-0.13.4.0 which failed to install.
diagrams-gtk-1.3.0.1 depends on glib-0.13.4.0 which failed to install.
gio-0.13.3.0 depends on glib-0.13.4.0 which failed to install.
glib-0.13.4.0 failed during the configure step. The exception was:
user error ('/usr/bin/ghc' exited with an error:

/tmp/cabal-tmp-18505/glib-0.13.4.0/dist/dist-sandbox-df16c69b/setup/setup.hs:5:8:
Could not find module ‘Gtk2HsSetup’
Use -v to see a list of the files searched for.
)
gtk-0.14.4 depends on glib-0.13.4.0 which failed to install.
pango-0.13.3.0 depends on glib-0.13.4.0 which failed to install.

$ cabal install cabal
$ cabal install diagrams

Sorry, I guess this example is pretty minimal, but it works..

If you replace the line marked FIRST with the line marked SECOND, then
the diagram flips upside down, and I have no idea why.

Any help would be helpful...
Stefan


> import Control.Monad.Trans ( liftIO )
> import Graphics.UI.Gtk
> import Diagrams.Backend.Cairo
> import Diagrams.Backend.Gtk
> import Diagrams.Prelude

> import           Diagrams.Prelude                hiding (height, width)
> import           Diagrams.Backend.Cairo.Internal
> import           Graphics.UI.Gtk
> import qualified Graphics.Rendering.Cairo        as CG



I was wondering why `defaultRender` requires a `DrawingArea` as
argument [1], but only gets a window from it to draw on [2].  In
contrast, `renderToGtk` is happy with a something of type
`DrawableClass dc => dc` [1].

Why is that?

Why would I want it differently?  I want to have a window that
rescales the diagram contents when it gets resized.  I'm a GUI-noob,
so I took GTK integration from [3]:

> main :: IO ()
> main
>   = do initGUI
>        canvas <- drawingAreaNew
>        canvas `on` sizeRequest $ return (Requisition 200 200)
>        canvas `on` exposeEvent $ renderFigure myFigure   -- below
>        window <- windowNew
>        Graphics.UI.Gtk.set window [ containerChild := canvas]
>        onDestroy window mainQuit
>        widgetShowAll window
>        mainGUI

> renderFigure :: Diagram B -> EventM EExpose Bool
> renderFigure dia = do
>    win <- eventWindow

>    liftIO . renderToGtk win . toGtkCoords $ scale 15 dia     -- FIRST

Above line does not rescale the diagram when the window is resized, so
I wanted to have something like the following:

  >    liftIO . defaultRender' win . toGtkCoords $ dia   -- SECOND

>    return True


Having a look at the sources [2], I decided that I could build such a
`defaultRender'` on my own, basically simplifying `defaultRender` from
[2]:

> defaultRender' :: (Monoid' m, DrawableClass dc)
>                => dc -> QDiagram Cairo V2 Double m -> IO ()
> defaultRender' drawable diagram
>   = renderDoubleBuffered drawable opts diagram
>   where
>     opts w h
>       = CairoOptions
>         { _cairoFileName     = ""
>         , _cairoSizeSpec     = dims (V2 (fromIntegral w) (fromIntegral h))
>         , _cairoOutputType   = RenderOnly
>         , _cairoBypassAdjust = False
>         }

Now if you exchange the two lines marked FIRST and SECOND above, then
this diagram actually scales nicely.  But why on earth is it upside
down?  In case you do not see this: On my machine it is mirrored on
the horizontal line!




To make the example work, I also copied the following 4 functions
from [2]...

> renderDoubleBuffered ::
>   (Monoid' m, DrawableClass dc) =>
>   dc -- ^ drawable to render onto
>   -> (Int -> Int -> Options Cairo V2 Double) -- ^ options, depending on drawable width and height
>   -> QDiagram Cairo V2 Double m -- ^ Diagram
>   -> IO ()
> renderDoubleBuffered drawable renderOpts diagram = do
>   (w,h) <- drawableGetSize drawable
>   let opts = renderOpts w h
>       renderAction = delete w h >> snd (renderDia Cairo opts diagram)
>   renderWithDrawable drawable (doubleBuffer renderAction)
> 
> delete :: Int -> Int -> CG.Render ()
> delete w h = do
>   CG.setSourceRGB 1 1 1
>   CG.rectangle 0 0 (fromIntegral w) (fromIntegral h)
>   CG.fill

> doubleBuffer :: CG.Render () -> CG.Render ()
> doubleBuffer renderAction = do
>   CG.pushGroup
>   renderAction
>   CG.popGroupToSource
>   CG.paint

...and took an example from diagram's tutorial [4].

> node :: Int -> Diagram B
> node n = text (show n) # fontSizeL 1 # fc white <> circle 1 # fc green

> myFigure :: Diagram B
> myFigure = atPoints (trailVertices $ regPoly 6 5) $ map node [1..]


____________________
[1] https://s3.amazonaws.com/haddock.stackage.org/lts-6.1/diagrams-gtk-1.3.0.1/Diagrams-Backend-Gtk.html
[2] https://s3.amazonaws.com/haddock.stackage.org/lts-6.1/diagrams-gtk-1.3.0.1/src/Diagrams-Backend-Gtk.html#defaultRender
[3] http://stackoverflow.com/questions/11885373/how-do-i-use-the-diagrams-library-with-gtk-drawables
[4] http://projects.haskell.org/diagrams/doc/quickstart.html