replace PLOTS_DEFAULT_BACKEND by Preferences

src/Plots.jl

@@ -199,9 +199,11 @@ include("init.jl")
 
 include("backends/plotly.jl")
 include("backends/web.jl")
-include("backends/gr.jl")
 
 include("shorthands.jl")
-include("precompile.jl")
+@static if backend(_pick_default_backend()) == GRBackend()
+    include("backends/gr.jl")
+    include("precompile.jl")
+end
 
 end

src/backends.jl

@@ -36,8 +36,6 @@ macro init_backend(s)
     end |> esc
 end
 
-# include("backends/web.jl")
-
 # ---------------------------------------------------------
 
 # don't do anything as a default
@@ -131,20 +129,24 @@ CurrentBackend(sym::Symbol) = CurrentBackend(sym, _backend_instance(sym))
 
 # ---------------------------------------------------------
 
-_fallback_default_backend() = backend(GRBackend())
+_fallback_default_backend() = :gr
+function _default_backend()
+    env_default = get(ENV, "PLOTS_DEFAULT_BACKEND", "")
+    if env_default != ""
+        Symbol(lowercase(env_default))
+    else
+        _fallback_default_backend()
+    end
+end
 
 function _pick_default_backend()
-    if (env_default = get(ENV, "PLOTS_DEFAULT_BACKEND", "")) != ""
-        if (sym = Symbol(lowercase(env_default))) in _backends
-            backend(sym)
-        else
-            @warn """You have set PLOTS_DEFAULT_BACKEND=$env_default, but it is not a valid backend package.
-            Choose from: \n\t$(join(sort(_backends), "\n\t"))
-            """
-            _fallback_default_backend()
-        end
+    if (sym = _default_backend()) in _backends
+        backend(sym)
     else
-        _fallback_default_backend()
+        @warn """You have set $sym as the default backend, but it is not a valid backend package.
+        Choose from: \n\t$(join(sort(_backends), "\n\t"))
+        """
+        backend(_fallback_default_backend())
     end
 end
 
@@ -289,7 +291,7 @@ end
 # ------------------------------------------------------------------------------
 # gr
 
-_initialize_backend(pkg::GRBackend) = nothing  # COV_EXCL_LINE
+_initialize_backend(pkg::GRBackend) = @eval Plots import GR  # COV_EXCL_LINE
 
 const _gr_attr = merge_with_base_supported([
     :annotations,

src/backends/gr.jl

@@ -1204,8 +1204,8 @@ function gr_get_legend_geometry(vp, sp)
     span_hspace = span + pad  # part of the horizontal increment
     dx = (textw + (vertical ? 0 : span_hspace)) * get(ekw, :legend_wfactor, 1)
 
-    # This is to prevent that linestyle is obscured by large markers. 
-    # We are trying to get markers to not be larger than half the line length. 
+    # This is to prevent that linestyle is obscured by large markers.
+    # We are trying to get markers to not be larger than half the line length.
     # 1 / leg.dy translates base_factor to line length units (important in the context of size kwarg)
     # gr_legend_marker_to_line_factor is an empirical constant to translate between line length unit and marker size unit
     base_markersize = gr_legend_marker_to_line_factor[] * span / dy  # NOTE: arbitrarily based on horizontal measures !

src/init.jl

@@ -3,6 +3,7 @@ using Scratch
 using REPL
 
 const plotly_local_file_path = Ref{Union{Nothing,String}}(nothing)
+const BACKEND_PATH_GR = @path joinpath(@__DIR__, "backends", "gr.jl")
 const BACKEND_PATH_GASTON = @path joinpath(@__DIR__, "backends", "gaston.jl")
 const BACKEND_PATH_HDF5 = @path joinpath(@__DIR__, "backends", "hdf5.jl")
 const BACKEND_PATH_INSPECTDR = @path joinpath(@__DIR__, "backends", "inspectdr.jl")
@@ -63,6 +64,11 @@ function __init__()
             )
         end,
     )
+    if _default_backend() === :gr
+        @require GR = "28b8d3ca-fb5f-59d9-8090-bfdbd6d07a71" begin
+            include(BACKEND_PATH_GR)
+        end
+    end
 
     @require HDF5 = "f67ccb44-e63f-5c2f-98bd-6dc0ccc4ba2f" begin
         include(BACKEND_PATH_HDF5)

test/runtests.jl

@@ -48,6 +48,7 @@ for name in (
     "animations",
     "output",
     "backends",
+    "init",
 )
     @testset "$name" begin
         if get(ENV, "VISUAL_REGRESSION_TESTS_AUTO", "false") == "true" && name != "backends"

test/test_init.jl

@@ -0,0 +1,19 @@
+using Plots, Test
+
+const plots_path = escape_string(pkgdir(Plots))
+
+@testset "Default Backend" begin
+    out = withenv("PLOTS_DEFAULT_BACKEND" => "Plotly") do
+        run(```
+           $(Base.julia_cmd()) -E """
+               using Pkg
+               Pkg.activate(; temp = true)
+               Pkg.develop(path = \"$(plots_path)\")
+               using Test
+               using Plots
+               @test backend() == Plots.PlotlyBackend()
+               """
+           ```)
+    end
+    @test out.exitcode == 0
+end