Add knock knock example.

examples/knock_knock.hs

@@ -0,0 +1,61 @@
+#!/usr/bin/env stack
+-- stack runghc --package reanimate
+{-# LANGUAGE OverloadedStrings #-}
+module Main(main) where
+
+import Reanimate
+import Reanimate.Builtin.Documentation
+import Reanimate.Scene
+import Reanimate.LaTeX
+import Control.Lens
+import Control.Monad
+
+main :: IO ()
+main = reanimate $ docEnv $ mapA (withFillOpacity 1) $ sceneAnimation $ do
+  line1 <- newLaTeX ["$>$ ", "knock!", " ", "knock!"]
+  forM_ line1 $ \o ->
+    oModify o $
+      oTopY .~ (screenHeight/2)
+
+  oFadeIn (line1!!0) 1
+  oShow (line1!!1); wait 0.3
+  oShow (line1!!3); wait 0.6
+
+  line2 <- newLaTeX ["$>$ ", "who's there?"]
+  mapM_ (`placeBelow` head line1) line2
+
+  oFadeIn (line2!!0) 1
+  oDraw (line2!!1) 1
+  
+  line3 <- newLaTeX ["$>$ ", "$(\\lambda x . x)$"]
+  mapM_ (`placeBelow` head line2) line3
+
+  oFadeIn (line3!!0) 1
+  oFadeIn (line3!!1) 1
+
+  line4 <- newLaTeX ["$>$ ", "$(\\lambda x . x)$", " ", "who?"]
+  mapM_ (`placeBelow` head line3) line4
+
+  oFadeIn (line4!!0) 1
+  oFadeIn (line4!!1) 1
+  oDraw (line4!!3) 1
+
+  line5 <- newLaTeX ["$>$ ", "who?"]
+  mapM_ (`placeBelow` head line4) line5
+
+  oFadeIn (line5!!0) 1
+  oDraw (line5!!1) 1
+
+  wait 1
+
+placeBelow a b = do
+  bBot <- oRead b oBottomY
+  oModify a $
+    oTopY .~ bBot
+
+newLaTeX chunks = mapM newObject $ map (translate (-4) 0) $ latexChunks chunks
+
+oDraw o d = do
+  oShow o
+  oTweenS o d $ \t ->
+    oContext .= withFillOpacity (max 0 $ t*10-9) . partialSvg t