Rectangle update

[Mattriks]

• I've updated the documentation to reflect these changes
• I've updated the unit tests
• I've run the regression tests
• I've built the docs and confirmed these changes don't cause new errors
• I've tested Gadfly with this PR (tbd)

This PR:

• Fixes Rectangles not rotated correctly #133

Rectangles are now PolygonPrimitives, so they will obey Compose transformations:

θ = -π/10
img = compose(context(units=UnitBox(0,0,3,1)), fill(nothing), stroke("blue"),
    (context(), rectangle([0.3,1.3,2.3],[0.4],[0.4],[0.2]), stroke("silver")),
    (context(rotation=Rotation(-π/6,0.5,0.5)), rectangle(0.3,0.4,0.4,0.2)),
    (context(rotation=Rotation(θ,1.5,0.4)), line([(1.0,0.4),(2.0,0.4)]), stroke("black")),
    (context(mirror=Mirror(θ,1.5,0.4)), rectangle(1.3,0.4,0.4,0.2)),
    (context(shear=Shear(1.0,0.0,2.5,0.5)), rectangle(2.3,0.4,0.4,0.2)) 
)

[codecov-io]

Codecov Report

Merging #338 into master will increase coverage by 0.34%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #338      +/-   ##
==========================================
+ Coverage   37.13%   37.47%   +0.34%     
==========================================
  Files          18       18              
  Lines        3089     3082       -7     
==========================================
+ Hits         1147     1155       +8     
+ Misses       1942     1927      -15

Impacted Files	Coverage Δ
src/cairo_backends.jl	52.81% <ø> (-0.58%)	⬇️
src/pgf_backend.jl	49.78% <ø> (+1.45%)	⬆️
src/svg.jl	67.87% <ø> (-1.18%)	⬇️
src/form.jl	49.76% <83.33%> (+0.46%)	⬆️
src/fontfallback.jl	46.6% <0%> (-0.46%)	⬇️
src/measure.jl	49.16% <0%> (-0.02%)	⬇️
src/Compose.jl	15.11% <0%> (+3.06%)	⬆️
src/misc.jl	61.17% <0%> (+28.41%)	⬆️

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[bjarthur]

i hesitate to get rid of RectanglePrimitive because both cairo and pgf have rectangle primitives that might be more performant than polygons. is it too hard to support shear transformations for rectangles directly?

also, what about shear transformations for circles, ellipses, lines, curves, etc...

[Mattriks]

There are some potential issues with implementing transformations at backend level:

• a particular transformation might not exist for some backends
• a transformation (e.g. rotation) might be context independent at backend level
• nested transformation may not work (golden_rect.jl is an example of a nested transformation).

Compose avoids all these issues by implementing transformations at Compose level. The following code
shows that this works for most Forms (the exception is ellipse shear, I can do circle shear using ngon).
So rectangle is currently the odd shape out, and transformations of rectangle need to be supported at Compose level.

set_default_graphic_size(6.5inch, 6.5inch)

θ = -π/10
img1 = compose(context(units=UnitBox(0,0,3,1)), fill(nothing), stroke("blue"),
    (context(), circle([0.5,1.5,2.5],[0.5],[0.1]), stroke("silver")),
    (context(rotation=Rotation(-π/6,0.5,0.5)), ngon(0.5,0.5,0.1,30)),
    (context(rotation=Rotation(θ,1.5,0.4)), line([(1.0,0.4),(2.0,0.4)]), stroke("black")),
    (context(mirror=Mirror(θ,1.5,0.4)), circle(1.5,0.5,0.1)),
    (context(shear=Shear(1.0,0.0,2.5,0.5)), ngon(2.5,0.5,0.1,30)) 
)

img2 = compose(context(units=UnitBox(0,0,3,1)), fill(nothing), stroke("blue"),
    (context(), ellipse([0.5,1.5,2.5],[0.5],[0.2],[0.1]), stroke("silver")),
    (context(rotation=Rotation(-π/6,0.5,0.5)), ellipse(0.5,0.5,0.2,0.1)),
    (context(rotation=Rotation(θ,1.5,0.4)), line([(1.0,0.4),(2.0,0.4)]), stroke("black")),
    (context(mirror=Mirror(θ,1.5,0.4)), ellipse(1.5,0.5,0.2,0.1)),
    (context(shear=Shear(1.0,0.0,2.5,0.5)), ellipse(2.5,0.5,0.2,0.1)) 
)

X = [(x,y) for x in (0.5,1.5,2.5), y in (0.5, -0.5, 1.5, 0.5) ]
X[:,1] = [x.+(-0.2, 0.0) for x in X[:,1]]
X[:,4] = [x.+(0.2, 0.0) for x in X[:,4]]

img3 = compose(context(units=UnitBox(0,0,3,1)), fill(nothing), stroke("blue"),
    (context(), curve(X[:,1],X[:,2],X[:,3],X[:,4]), stroke("silver")),
    (context(rotation=Rotation(-π/6,0.5,0.5)), curve(X[1,:]...)),
    (context(rotation=Rotation(θ,1.5,0.4)), line([(1.0,0.4),(2.0,0.4)]), stroke("black")),
    (context(mirror=Mirror(θ,1.5,0.4)), curve(X[2,:]...)),
    (context(shear=Shear(1.0,0.0,2.5,0.5)), curve(X[3,:]...)) 
)
vstack(img1,img2,img3) 

[Mattriks]

Ran into errors testing on Gadfly with this PR. Looks like PolygonPrimitives need extra support for DateTime types ...

[bjarthur]

do PolygonPrimitives work yet with DateTime types?