Use Fontconfig to avoid the need for a font install

Author: Ickaser

.github/workflows/documentation.yaml

@@ -28,7 +28,6 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - uses: actions/checkout@v5
-      - run: sudo apt install -y fonts-freefont-ttf
       - uses: julia-actions/setup-julia@v2
         with:
           version: 1

docs/Project.toml

@@ -1,6 +1,7 @@
 [deps]
 Dates = "ade2ca70-3891-5945-98fb-dc099432e06a"
 Documenter = "e30172f5-a6a5-5a46-863b-614d45cd2de4"
+Fontconfig = "186bb1d3-e1f7-5a2c-a377-96d770f13627"
 InverseFunctions = "3587e190-3f89-42d0-90ee-14403ec27112"
 LaTeXStrings = "b964fa9f-0449-5b57-a5c2-d3ea65f4040f"
 Latexify = "23fbe1c1-3f47-55db-b15f-69d7ec21a316"
@@ -16,3 +17,4 @@ Unitful = {path = ".."}
 Documenter = "1"
 Latexify = "0.16.9"
 Plots = "1"
+Fontconfig = "0.4"

docs/generate_latex_images.jl

@@ -1,5 +1,10 @@
 using LaTeXStrings, Unitful, Latexify
 import tectonic_jll # needed for lightweight LaTeX render
+using Fontconfig: format, match, Pattern
+
+# Since the docs can get built on different systems, we need to find a locally installed 
+# monospaced font that has enough Unicode coverage to handle π
+monofont = format(match(Pattern(spacing=100, charset="3c0")), "%{family}")
 
 commands = [
     :(latexify(612.2u"nm")),
@@ -20,11 +25,16 @@ end
 ltab1 = latextabular(tab1, adjustment=:l, transpose=true, latex=false, booktabs=true, 
     head=["julia", "\\LaTeX", "Result"])
 # Setting an explicit white background color results in transparent PDF, so go offwhite.
-ltab1 = LaTeXString("\\definecolor{offwhite}{rgb}{0.999,0.999,0.999}\n\\pagecolor{offwhite}\n\\color{black}\n" * ltab1)
+ltab1 = LaTeXString("""
+    \\setmonofont{$monofont}
+    \\definecolor{offwhite}{rgb}{0.999,0.999,0.999}
+    \\pagecolor{offwhite}
+    \\color{black}
+""" * ltab1)
 
 render(ltab1, MIME("image/png"); use_tectonic=true,
     name=(@__DIR__)*"/src/assets/latex-examples", 
-    packages=["booktabs", "color", "siunitx"], 
+    packages=["booktabs", "color", "siunitx", "fontspec"], 
     documentclass=("standalone"))
 
 functions = [
@@ -134,8 +144,7 @@ ltab2 = latextabular(tab2, adjustment=:l, transpose=true, latex=false, booktabs=
 # Set background to not-quite-white so it doesn't get treated as transparent
 ltab2 = LaTeXString(
     """
-    \\setmainfont{FreeSerif}
-    \\setmonofont{FreeMono}
+    \\setmonofont{$monofont}
     \\definecolor{offwhite}{rgb}{0.999,0.999,0.999}
     \\pagecolor{offwhite}
     \\color{black}