Rectangle update

[Mattriks]

• [x] I've updated the documentation to reflect these changes
• [x] I've updated the unit tests
• [x] I've run the regression tests
• [x] 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 #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%)	:arrow_down:
src/pgf_backend.jl	49.78% <ø> (+1.45%)	:arrow_up:
src/svg.jl	67.87% <ø> (-1.18%)	:arrow_down:
src/form.jl	49.76% <83.33%> (+0.46%)	:arrow_up:
src/fontfallback.jl	46.6% <0%> (-0.46%)	:arrow_down:
src/measure.jl	49.16% <0%> (-0.02%)	:arrow_down:
src/Compose.jl	15.11% <0%> (+3.06%)	:arrow_up:
src/misc.jl	61.17% <0%> (+28.41%)	:arrow_up:

---

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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?