Set viewbox to 16 by 9. (#11)

* Set viewbox to 16 by 9.

* Update examples and fix process termination bug in driver.

* Add module for constants.


Former-commit-id: 1c77569e771455e674485e2fc58ee57e7df5f3c5

examples/boundingbox.hs

@@ -11,14 +11,15 @@ import           Reanimate.LaTeX
 import           Reanimate.Monad
 import           Reanimate.Svg
 import           Reanimate.Signal
+import           Reanimate.Constants
 
 main :: IO ()
 main = reanimate bbox
 
 bbox :: Animation
 bbox = bg `sim`
-    mapA (translate (-50) 0) bbox1 `sim`
-    mapA (translate 50 0) bbox2
+    mapA (translate (-screenWidth/4) 0) bbox1 `sim`
+    mapA (translate (screenWidth/4) 0) bbox2
   where
     bg = mkAnimation 0 $ emit $ mkBackground "black"
 
@@ -29,14 +30,15 @@ bbox1 = mkAnimation 5 $ do
       [ mkBoundingBox $ rotate (360*s) svg
       , withFillColor "white" $ rotate (360*s) svg ]
   where
-    svg = scale 3 $ center $ latexAlign "\\sum_{k=1}^\\infty"
+    svg = scale 2 $ center $ latexAlign "\\sum_{k=1}^\\infty"
 
 bbox2 :: Animation
 bbox2 = autoReverse $ mkAnimation 2.5 $ do
   s <- getSignal signalLinear
   emit $ mkGroup
     [ mkBoundingBox $ partialSvg s heartShape
-    , withStrokeColor "white" $ withFillOpacity 0 $ partialSvg s heartShape ]
+    , withStrokeColor "white" $ withFillOpacity 0 $
+      partialSvg s heartShape ]
 
 mkBoundingBox :: Tree -> Tree
 mkBoundingBox svg = withStrokeColor "red" $ withFillOpacity 0 $
@@ -45,7 +47,7 @@ mkBoundingBox svg = withStrokeColor "red" $ withFillOpacity 0 $
   where
     (x, y, w, h) = boundingBox svg
 
-heartShape =
+heartShape = lowerTransformations $ scaleXY 1 (-1) $ scale 0.1 $
     center $ rotateAroundCenter 225 $ mkPathString
       "M0.0,40.0 v-40.0 h40.0\
       \a20.0 20.0 90.0 0 1 0.0,40.0\