Lenses for setting arrow head, tail, and shaft colors #138
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added 11 commits
November 14, 2013 11:44
This allows (partial) conversions in both directions, which I found necessary for implementing some lenses to set some color in a given style. Adding such a method seems generally unobjectionable to me.
These are intentionally not re-exported from the Prelude; most users should not need them.
This is the sort of convenient thing that we can do now that we use lens for everything: we can provide headColor, tailColor, and shaftColor directly as "virtual fields" so the user doesn't have to think about style modification functions in the common case where they just want to set the color (and we also protect them from the easy mistake of setting the line color on the head, or fill color on the shaft). This is something of a proof-of-concept. Ideally we could even refactor these as e.g. headColor = headStyle . styleFillColor where styleFillColor :: (Color c, Color c') => Setter (Style v) (Style v) c c'.
Not sure why we were missing this before.
Note these can't be lenses because there's nothing to return if the style does not contain a line or fill color attribute. (One could just return a default value but that would violate the lens laws.) Seems to work pretty well! Perhaps we should add setters for other attributes as well.
…tyle{Line,Fill}Color
The more polymorphic versions caused problems for type inference in typical use cases.
The shaft width will now be taken from the ambient line width attribute by default. Explicitly setting the line width via the shaftStyle will always override this default.
bergey
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Nov 16, 2013
Lenses for setting arrow head, tail, and shaft colors
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This pull request contains the following:
Colorclass,fromAlphaColour. See @9a89228.Diagrams.Attributes. See @a9339c6.Default FillColorinstance. Not sure why it was missing before.lwfunction to an arrow, as well as by setting theshaftStyle.Generally I am excited about the possibility of providing more of these sorts of "virtual fields" --- lenses which allow you to query, modify, or traverse some aspect of a thing even when that aspect is not actually a literal record field.