use poly in axis background, test that no rasterization happens in ba…

…sic svgs (#1734)

* use poly in axis background, test that no rasterization happens in basic svgs

* add notice

CairoMakie/test/runtests.jl

@@ -15,6 +15,8 @@ Pkg.develop(PackageSpec(path = path))
     end
 end
 
+include(joinpath(@__DIR__, "svg_tests.jl"))
+
 using ReferenceTests
 using ReferenceTests: database_filtered
 

CairoMakie/test/svg_tests.jl

@@ -0,0 +1,20 @@
+# guard against some future changes silently making simple vector graphics be
+# rasterized if they are using features unsupported by the SVG spec
+function svg_isnt_rasterized(x)
+    mktempdir() do path
+        path = joinpath(path, "test.svg")
+        save(path, x)
+        # this is rough but an easy way to catch rasterization,
+        # if an image element is present in the svg
+        return !occursin("<image id=", read(path, String))
+    end
+end
+
+@testset "SVG rasterization" begin
+    @test svg_isnt_rasterized(Scene())
+    @test svg_isnt_rasterized(begin f = Figure(); Axis(f[1, 1]); f end)
+    @test svg_isnt_rasterized(scatter(1:3))
+    @test svg_isnt_rasterized(lines(1:3))
+    @test svg_isnt_rasterized(heatmap(rand(5, 5)))
+    @test !svg_isnt_rasterized(image(rand(5, 5)))
+end

src/makielayout/layoutables/axis.jl

@@ -74,7 +74,9 @@ function layoutable(::Type{<:Axis}, fig_or_scene::Union{Figure, Scene}; bbox = n
 
     scene = Scene(topscene, px_area=scenearea)
 
-    background = mesh!(topscene, scenearea, color = backgroundcolor, inspectable = false, shading=false)
+    # TODO: replace with mesh, however, CairoMakie needs a poly path for this signature
+    # so it doesn't rasterize the scene
+    background = poly!(topscene, scenearea, color = backgroundcolor, inspectable = false, shading = false, strokecolor = :transparent)
     translate!(background, 0, 0, -100)
     decorations[:background] = background