add src/backends/plotlybase.jl

src/backends/plotlybase.jl

@@ -0,0 +1,23 @@
+function plotlybase_syncplot(plt::Plot)
+    plt.o = PlotlyBase.Plot()
+    traces = PlotlyBase.GenericTrace[]
+    for series_dict in plotly_series(plt)
+        plotly_type = pop!(series_dict, :type)
+        push!(traces, PlotlyBase.GenericTrace(plotly_type; series_dict...))
+    end
+    PlotlyBase.addtraces!(plt.o, traces...)
+    layout = plotly_layout(plt)
+    w, h = plt[:size]
+    PlotlyBase.relayout!(plt.o, layout, width = w, height = h)
+    return plt.o
+end
+
+for (mime, fmt) in (
+    "application/pdf" => "pdf",
+    "image/png" => "png",
+    "image/svg+xml" => "svg",
+    "image/eps" => "eps",
+)
+    @eval _show(io::IO, ::MIME{Symbol($mime)}, plt::Plot{PlotlyBackend}) =
+        PlotlyBase.savefig(io, plotlybase_syncplot(plt), format = $fmt)
+end