Allow for poly to work with empty polygons (#3146)

* Fix empty polygon plotting * fix error on Point2f[] * fix error on Polygon[] * add mor conversion tests for empty inputs --------- Co-authored-by: ffreyer <frederic481994@hotmail.de> Co-authored-by: Simon <sdanisch@protonmail.com>
MakieOrg · Aug 14, 2023 · c6c3a0e · c6c3a0e
1 parent f1fb6c0
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Showing 4 changed files with 35 additions and 3 deletions.
diff --git a/CairoMakie/src/overrides.jl b/CairoMakie/src/overrides.jl
@@ -102,6 +102,7 @@ function draw_poly(scene::Scene, screen::Screen, poly, rects::Vector{<:Rect2})
 end
 
 function polypath(ctx, polygon)
+    isempty(polygon) && return nothing
     ext = decompose(Point2f, polygon.exterior)
     Cairo.set_fill_type(ctx, Cairo.CAIRO_FILL_RULE_EVEN_ODD)
     Cairo.move_to(ctx, ext[1]...)

diff --git a/ReferenceTests/src/tests/examples2d.jl b/ReferenceTests/src/tests/examples2d.jl
@@ -1120,6 +1120,18 @@ end
     fig
 end
 
+@reference_test "Plotting empty polygons" begin
+    p = Makie.Polygon(Point2f[])
+    q = Makie.Polygon(Point2f[(-1.0, 0.0), (1.0, 0.0), (0.0, 1.0)])
+    fig, ax, sc = poly([p, q])
+    poly!(Axis(fig[1,2]), p, color = :black)
+    poly!(Axis(fig[2,1]), [p, q], color = [:red, :blue])
+    poly!(Axis(fig[2,2]), [p, q], color = :red)
+    poly!(Axis(fig[3,1]), Makie.MultiPolygon([p]), color = :green)
+    poly!(Axis(fig[3,2]), Makie.MultiPolygon([p, q]), color = [:black, :red])
+    fig
+end 
+
 @reference_test "lines (some with NaNs) with array colors" begin
     f = Figure()
     ax = Axis(f[1, 1])

diff --git a/src/basic_recipes/poly.jl b/src/basic_recipes/poly.jl
@@ -41,7 +41,11 @@ function poly_convert(geometries)
     return triangle_mesh.(geometries)
 end
 poly_convert(meshes::AbstractVector{<:AbstractMesh}) = meshes
-poly_convert(polys::AbstractVector{<:Polygon}) = triangle_mesh.(polys)
+function poly_convert(polys::AbstractVector{<:Polygon})
+    # GLPlainMesh2D is not concrete?
+    T = GeometryBasics.Mesh{2, Float32, GeometryBasics.Ngon{2, Float32, 3, Point2f}, SimpleFaceView{2, Float32, 3, GLIndex, Point2f, GLTriangleFace}}
+    return isempty(polys) ? T[] : triangle_mesh.(polys)
+end
 function poly_convert(multipolygons::AbstractVector{<:MultiPolygon})
     return [merge(triangle_mesh.(multipoly.polygons)) for multipoly in multipolygons]
 end
@@ -82,7 +86,7 @@ end
 
 function to_lines(polygon::AbstractVector{<: VecTypes})
     result = Point2f.(polygon)
-    push!(result, polygon[1])
+    isempty(result) || push!(result, polygon[1])
     return result
 end
 

diff --git a/test/conversions.jl b/test/conversions.jl
@@ -278,12 +278,27 @@ end
 
 
 @testset "empty poly" begin
+    # Geometry Primitive
     f, ax, pl = poly(Rect2f[]);
     pl[1] = [Rect2f(0, 0, 1, 1)];
     @test pl.plots[1][1][] == [GeometryBasics.triangle_mesh(Rect2f(0, 0, 1, 1))]
 
-    f, ax, pl = poly(Vector{Point2f}[])
+    # Empty Polygon
+    f, ax, pl = poly(Polygon(Point2f[]));
+    pl[1] = Polygon(Point2f[(1,0), (1,1), (0,1)]);
+    @test pl.plots[1][1][] == GeometryBasics.triangle_mesh(pl[1][])
+
+    f, ax, pl = poly(Polygon[]);
+    pl[1] = [Polygon(Point2f[(1,0), (1,1), (0,1)])];
+    @test pl.plots[1][1][] == GeometryBasics.triangle_mesh.(pl[1][])
+
+    # PointBased inputs
+    f, ax, pl = poly(Point2f[])
     points = decompose(Point2f, Circle(Point2f(0),1))
+    pl[1] = points
+    @test pl.plots[1][1][] == Makie.poly_convert(points)
+
+    f, ax, pl = poly(Vector{Point2f}[])
     pl[1] = [points]
     @test pl.plots[1][1][] == Makie.poly_convert(points)
 end