Allow anything to convert to a doc if it's showable to that mimetype

src/types.jl

@@ -130,6 +130,42 @@ Base.convert(::Type{Matrix{ARGB32}}, cached::AbstractCachedDocument) = rasterize
 
 Base.size(cached::AbstractCachedDocument) = cached.dims
 
+#=
+### Convert arbitrary Julia objects to Documents
+
+TODOs: 
+- Allow the conversion to use the constructor, if there is a method.
+=#
+
+
+function Base.convert(T::Type{<: AbstractDocument}, x)
+    if !showable(mimetype(T), x)
+        error("Object of type $(typeof(x)) is not showable as mime type $(mimetype(T)).")
+    end
+    return T(sprint(show, mimetype(T), x))
+end
+# This resolves an ambiguity otherwise.
+Base.convert(::Type{T}, x::T) where T <: AbstractDocument = x
+
+function Base.convert(::Type{AbstractDocument}, x)
+    for DocType in [TEXDocument, TypstDocument, SVGDocument, PDFDocument]
+        if showable(mimetype(DocType), x)
+            return convert(DocType, x)
+        end
+    end
+    error("MakieTeX: Object of type $(typeof(x)) is not showable as an AbstractDocument.")
+end
+
+
+function Base.convert(::Type{AbstractCachedDocument}, x)
+    for DocType in [CachedTEX, CachedTypst, CachedSVG, CachedPDF]
+        if showable(mimetype(DocType), x)
+            return convert(DocType, x)
+        end
+    end
+    error("MakieTeX: Object of type $(typeof(x)) is not showable as an AbstractCachedDocument.")
+end
+
 #=
 
 ### Makie.jl function definitions
@@ -277,6 +313,18 @@ Available keyword arguments are:
 """
 texdoc(contents; kwargs...) = TEXDocument(contents, true; kwargs...)
 
+function Base.convert(::Type{TEXDocument}, x)
+    if !showable(mimetype(TEXDocument), x)
+        error("Object of type $(typeof(x)) is not showable as mime type $(mimetype(TEXDocument)).")
+    end
+    texstring = sprint(show, mimetype(TEXDocument), x)
+    if contains(texstring, "\\begin{document}")
+        return TEXDocument(texstring, false) # assume this to be a fixed document
+    else
+        return TEXDocument(texstring, true) # assume this to require a preamble
+    end
+end
+
 struct TypstDocument <: AbstractDocument
     contents::String
     page::Int

test/integrations.jl

@@ -0,0 +1,23 @@
+using DataFrames
+
+using SummaryTables
+data = DataFrame(
+    sex = ["m", "m", "m", "m", "f", "f", "f", "f", "f", "f"],
+    age = [27, 45, 34, 85, 55, 44, 24, 29, 37, 76],
+    blood_type = ["A", "0", "B", "B", "B", "A", "0", "A", "A", "B"],
+    smoker = [true, false, false, false, true, true, true, false, false, false],
+)
+
+tab = table_one(
+    data,
+    [:age => "Age (years)", :blood_type => "Blood type", :smoker => "Smoker"],
+    groupby = :sex => "Sex",
+    show_n = true
+)
+
+tex = convert(TEXDocument, tab)
+typst = convert(TypstDocument, tab)
+
+
+@test_broken teximg(tex)
+@test_nowarn teximg(typst)