Build PDF docs instead of HTML

Sphinx-generated HTML documentation is not suitable for packaging; see
https://bugzilla.redhat.com/show_bug.cgi?id=2006555 for discussion.

gi-docgen.spec

@@ -1,6 +1,12 @@
 %global forgeurl https://gitlab.gnome.org/GNOME/%{name}/
 %global tag %{version}
 
+# Sphinx-generated HTML documentation is not suitable for packaging; see
+# https://bugzilla.redhat.com/show_bug.cgi?id=2006555 for discussion.
+#
+# We can generate PDF documentation as a lesser substitute.
+%bcond_without doc_pdf
+
 Name:           gi-docgen
 Version:        2021.7
 %forgemeta
@@ -46,9 +52,13 @@ BuildArch:      noarch
 BuildRequires:  python3-devel
 
 # Documentation
+%if %{with doc_pdf}
 BuildRequires:  make
 BuildRequires:  python3dist(sphinx)
 BuildRequires:  python3dist(sphinx-rtd-theme)
+BuildRequires:  python3-sphinx-latex
+BuildRequires:  latexmk
+%endif
 
 # Unbundling fonts:
 BuildRequires:  font(redhatdisplay)
@@ -136,8 +146,10 @@ find . -type f \( -name '*.woff' -o -name '*.woff2' \) -print -delete
 %build
 %pyproject_wheel
 
-%make_build -C docs
-rm -rvf docs/_build/.buildinfo docs/_build/.doctrees
+%if %{with doc_pdf}
+sphinx-build -b latex docs %{_vpath_builddir}/_latex
+%make_build -C %{_vpath_builddir}/_latex
+%endif
 
 
 %install
@@ -149,7 +161,10 @@ install -t '%{buildroot}%{_pkgdocdir}' -D -m 0644 -p \
     CONTRIBUTING.md \
     docs/CODEOWNERS \
     README.md
-cp -rp docs/_build '%{buildroot}%{_pkgdocdir}/html'
+%if %{with doc_pdf}
+install -t '%{buildroot}%{_pkgdocdir}' -p -m 0644 \
+    '%{_vpath_builddir}/_latex/gi-docgen.pdf'
+%endif
 cp -rp examples '%{buildroot}%{_pkgdocdir}/'