haskellgraphicshaskell-diagrams

Diagrams boundingRect including the lines' width

Is there an equivalent to the boundingRect function which includes the diagram's lines width(*), so that each line, however thick it is, is entirely contained within the bounding rectangle? (the boundingRect function "ignores" their thickness and parts of the lines stay outside the bounding rectangle).

(*) My question is for lines with width expressed in local units.

Solution

  • Unfortunately there's no way to do this automatically yet. The easiest way would be to frame the diagram before finding the boundingRect. Since you're using the local units you just need to frame half the local width used in the diagram (add half of the line width used for the bounding rectangle if that has a line too).

    Here's a simple example:

    {-# LANGUAGE GADTs #-}

import Diagrams.Prelude
import Diagrams.Backend.Rasterific.CmdLine

main :: IO ()
main = mainWith $ frame 1 rects

rects :: Diagram B
rects = hsep 1 $ map (dia <>) [br1, br2, br3]
  where
    br1 = boundingRect dia # lwL 0.2 # lc red
    br2 = boundingRect (frame 0.1 dia) # fc dodgerblue # lw none
    br3 = boundingRect (frame 0.2 dia) # lwL 0.2 # lc red

dia :: Diagram B
dia = circle 3 # fc orange # lwL 0.2

    bounding rectangles

    A more general solution would be to draw the offset curves of each path using the local line width in the Diagram and find the bounding box of that. Diagrams.TwoD.Offset can almost do this but I don't think it works for all cases.