Add TranformedDomain (#1153)

* Add 'TranformedDomain'

* Add docstring

* Add some tests

* Fix typo

* Add more tests

* Add comments

Author: eliascarv

src/Meshes.jl

@@ -289,6 +289,7 @@ export
   # domain traits
   Domain,
   SubDomain,
+  TransformedDomain,
   embeddim,
   paramdim,
   crs,

src/domains.jl

@@ -143,6 +143,7 @@ include("domains/sets.jl")
 include("domains/meshes.jl")
 include("domains/trajecs.jl")
 include("domains/subdomains.jl")
+include("domains/transformeddomain.jl")
 
 # ------------
 # CONVERSIONS

src/domains/transformeddomain.jl

@@ -0,0 +1,34 @@
+# ------------------------------------------------------------------
+# Licensed under the MIT License. See LICENSE in the project root.
+# ------------------------------------------------------------------
+
+"""
+    TransformedDomain(domain, transform)
+
+Lazy representation of a geometric `transform` applied to a `domain`.
+"""
+struct TransformedDomain{M<:Manifold,C<:CRS,D<:Domain,T<:Transform} <: Domain{M,C}
+  domain::D
+  transform::T
+
+  function TransformedDomain{M,C}(domain::D, transform::T) where {M<:Manifold,C<:CRS,D<:Domain,T<:Transform}
+    new{M,C,D,T}(domain, transform)
+  end
+end
+
+function TransformedDomain(d::Domain, t::Transform)
+  g = t(first(d))
+  TransformedDomain{manifold(g),crs(g)}(d, t)
+end
+
+# specialize constructor to avoid deep structures
+TransformedDomain(d::TransformedDomain, t::Transform) = TransformedDomain(d.domain, d.transform → t)
+
+Base.parent(d::TransformedDomain) = d.domain
+
+transform(d::TransformedDomain) = d.transform
+
+# domain interface
+element(d::TransformedDomain, ind::Int) = d.transform(element(d.domain, ind))
+
+nelements(d::TransformedDomain) = nelements(d.domain)

test/transformeddomain.jl

@@ -0,0 +1,73 @@
+@testitem "TransformedDomain" setup = [Setup] begin
+  # constructor
+  pset = PointSet(randpoint2(10))
+  trans1 = Scale(T(2), T(2))
+  trans2 = Translate(T(4), T(4))
+  tpset1 = TransformedDomain(pset, trans1)
+  @test parent(tpset1) == pset
+  @test Meshes.transform(tpset1) == trans1
+  tpset2 = TransformedDomain(tpset1, trans2)
+  @test parent(tpset2) == pset
+  @test Meshes.transform(tpset2) == (trans1 → trans2)
+
+  pset = PointSet(randpoint2(10))
+  trans = Identity()
+  tpset = TransformedDomain(pset, trans)
+  @test nelements(tpset) == nelements(pset)
+  @test element(tpset, 1) == element(pset, 1)
+  @test tpset == pset
+  trans = Translate(T(2), T(2))
+  tpset = TransformedDomain(pset, trans)
+  @test nelements(tpset) == nelements(pset)
+  @test element(tpset, 1) == trans(element(pset, 1))
+  @test tpset == trans(pset)
+
+  t1 = Triangle(cart(0, 0), cart(1, 0), cart(0, 1))
+  t2 = Triangle(cart(1, 1), cart(2, 1), cart(1, 2))
+  gset = GeometrySet([t1, t2])
+  trans = Identity()
+  tgset = TransformedDomain(gset, trans)
+  @test nelements(tgset) == nelements(gset)
+  @test element(tgset, 1) == element(gset, 1)
+  @test tgset == gset
+  trans = Translate(T(2), T(2))
+  tgset = TransformedDomain(gset, trans)
+  @test nelements(tgset) == nelements(gset)
+  @test element(tgset, 1) == trans(element(gset, 1))
+  @test tgset == trans(gset)
+
+  grid = cartgrid(10, 10)
+  trans = Identity()
+  tgrid = TransformedDomain(grid, trans)
+  @test nelements(tgrid) == nelements(grid)
+  @test element(tgrid, 1) == element(grid, 1)
+  @test tgrid == grid
+  trans = Translate(T(2), T(2))
+  tgrid = TransformedDomain(grid, trans)
+  @test nelements(tgrid) == nelements(grid)
+  @test element(tgrid, 1) == trans(element(grid, 1))
+  @test tgrid == trans(grid)
+
+  grid = cartgrid(10, 10)
+  subgrid = view(grid, 1:10)
+  trans = Identity()
+  tsubgrid = TransformedDomain(subgrid, trans)
+  @test nelements(tsubgrid) == nelements(subgrid)
+  @test element(tsubgrid, 1) == element(subgrid, 1)
+  @test tsubgrid == subgrid
+  trans = Translate(T(2), T(2))
+  tsubgrid = TransformedDomain(subgrid, trans)
+  @test nelements(tsubgrid) == nelements(subgrid)
+  @test element(tsubgrid, 1) == trans(element(subgrid, 1))
+  @test tsubgrid == trans(subgrid)
+
+  # transforms that change the CRS
+  pset = PointSet(latlon(0, 0), latlon(0, 45), latlon(45, 0))
+  trans = Proj(Mercator)
+  tpset = TransformedDomain(pset, trans)
+  @test manifold(tpset) === 𝔼{2}
+  @test crs(tpset) <: Mercator
+  @test nelements(tpset) == nelements(pset)
+  @test element(tpset, 1) == trans(element(pset, 1))
+  @test tpset == trans(pset)
+end