Optimize centroid of TransformedMesh (#995)

* Optimize centroid of TransformedMesh

* Update test/mesh.jl

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

---------

Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

Author: juliohm

src/mesh/transformedmesh.jl

@@ -33,6 +33,8 @@ topology(m::TransformedMesh) = topology(m.mesh)
 
 vertex(m::TransformedMesh, ind::Int) = m.transform(vertex(m.mesh, ind))
 
+centroid(m::TransformedMesh, ind::Int) = m.transform(centroid(m.mesh, ind))
+
 # alias to improve readability in IO methods
 const TransformedGrid{M<:Manifold,C<:CRS,Dim,G<:Grid,TR<:Transform} = TransformedMesh{M,C,GridTopology{Dim},G,TR}
 

test/mesh.jl

@@ -759,6 +759,13 @@
     @test minimum(sub) == cart(0, 2)
     @test maximum(sub) == cart(10, 7)
 
+    # optimization of centroid
+    trans = Rotate(T(π / 4))
+    cgrid = cartgrid(10, 10)
+    tmesh = Meshes.TransformedMesh(cgrid, trans)
+    centr = centroid(tmesh, 1)
+    @test @allocated(centroid(tmesh, 1)) < 50
+
     @test sprint(show, tgrid) == "10×10 TransformedGrid"
     if T == Float32
       @test sprint(show, MIME"text/plain"(), tgrid) == """