83 lines
2.6 KiB
Haskell
83 lines
2.6 KiB
Haskell
-- | A module for rendering lines as an HTML5 file containing an SVG image.
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-- This can be used to visualize the denotational semantics of a MiniLogo
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-- program.
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--
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-- NOTE: You should not change the definitions in this file!
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--
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module Render (Point,Line,toHTML,toGridHTML) where
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import Data.List (intercalate)
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-- | A point is a cartesian pair (x,y).
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type Point = (Int,Int)
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-- | A line is defined by its endpoints.
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type Line = (Point,Point)
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-- | Output a list of lines as an HTML5 file containing an SVG image.
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toHTML :: [Line] -> IO ()
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toHTML ls = writeFile "MiniMiniLogo.html" (header ++ content ls ++ footer)
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-- | Alternate version of 'toHTML' that adds a grid to the background.
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toGridHTML :: [Line] -> IO ()
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toGridHTML ls = writeFile "MiniMiniLogo.html" (header ++ grid ++ content ls ++ footer)
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--
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-- Private definitions. All definitions below this point will not be visible
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-- from within a module that imports this module.
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--
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scale, margin, width, height :: Int
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scale = 10
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margin = 10
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width = 800
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height = 400
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gridStep = 5
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maxX = width `div` scale
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maxY = height `div` scale
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gridStyle = "fill:none;stroke:lightgrey;stroke-width:1"
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drawStyle = "fill:none;stroke:red;stroke-width:2"
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title = "<head><title>MiniLogo Semantics Viewer</title></head>"
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view = "<svg width='100%' viewBox='0 0 "
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++ show (width + 2*margin) ++ " "
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++ show (height + 2*margin) ++ "'>"
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border = "<rect x='" ++ show (margin-3) ++
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"' y='" ++ show (margin-3) ++
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"' width='" ++ show (width +6) ++
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"' height='" ++ show (height+5) ++
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"' style='fill:none;stroke:black;stroke-width:2'/>"
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header = unlines ["<!DOCTYPE html>", "<html>", title, "<body>", view, border]
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footer = unlines ["</svg>","</body>","</html>"]
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grid = unlines (map (poly gridStyle) lines)
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where lines = [ [(x,0), (x,maxY)] | x <- [0,gridStep..maxX] ]
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++ [ [(0,y), (maxX,y)] | y <- [0,gridStep..maxY] ]
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content :: [Line] -> String
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content = unlines . map (poly drawStyle) . chunk
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-- | A canvas-adjusted point as a string.
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point :: Point -> String
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point (x,y) = show xp ++ "," ++ show yp
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where xp = x*scale + margin
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yp = height - y*scale + margin
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-- | Chunk a bunch of lines into sequences of connected points.
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chunk :: [Line] -> [[Point]]
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chunk [] = []
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chunk [(p,q)] = [[p,q]]
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chunk ((p,q):ls) | q == head ps = (p:ps) : pss
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| otherwise = [p,q] : ps : pss
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where (ps:pss) = chunk ls
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-- | Draw a sequence of connected points.
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poly :: String -> [Point] -> String
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poly style ps = "<polyline points='"
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++ intercalate " " (map point ps)
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++ "' style='" ++ style ++ "'/>"
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