From 71737b87f9c3729ba6d0969b032448073948a673 Mon Sep 17 00:00:00 2001
From: Juergen Spitzmueller <spitz@lyx.org>
Date: Mon, 18 Feb 2019 13:14:53 +0100
Subject: [PATCH] Basic support for biblatex-chicago

This uses a specific wrapper package that must be loaded instead of
biblatex.

Via "Requires biblatex-chicago", this is now possible.

For proper support, a citeengine file needs to be written

This commit here could also be backported to stable.
---
 lib/chkconfig.ltx    |  1 +
 src/BufferParams.cpp | 17 +++++++++++++----
 2 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/lib/chkconfig.ltx b/lib/chkconfig.ltx
index 4b78d88545..d8b027f001 100644
--- a/lib/chkconfig.ltx
+++ b/lib/chkconfig.ltx
@@ -285,6 +285,7 @@
 \TestPackage{babel}
 \TestPackage{beamerposter}
 \TestPackage{biblatex}
+\TestPackage{biblatex-chicago}
 \TestPackage{bibtopic}
 \TestPackage{bicaption}
 \TestPackage{bidi}
diff --git a/src/BufferParams.cpp b/src/BufferParams.cpp
index d57f68c0e9..60bfa3ab22 100644
--- a/src/BufferParams.cpp
+++ b/src/BufferParams.cpp
@@ -2348,19 +2348,25 @@ bool BufferParams::writeLaTeX(otexstream & os, LaTeXFeatures & features,
 	}
 
 	// ... but before biblatex (see #7065)
-	if (features.mustProvide("biblatex")
+	if ((features.mustProvide("biblatex")
+	     || features.isRequired("biblatex-chicago"))
+	    && !features.isProvided("biblatex-chicago")
 	    && !features.isProvided("biblatex-natbib")
 	    && !features.isProvided("natbib-internal")
 	    && !features.isProvided("natbib")
 	    && !features.isProvided("jurabib")) {
+		// The biblatex-chicago package has a differing interface
+		// it uses a wrapper package and loads styles via fixed options
+		bool const chicago = features.isRequired("biblatex-chicago");
 		string delim = "";
 		string opts;
 		os << "\\usepackage";
 		if (!biblatex_bibstyle.empty()
-		    && (biblatex_bibstyle == biblatex_citestyle)) {
+		    && (biblatex_bibstyle == biblatex_citestyle)
+		    && !chicago) {
 			opts = "style=" + biblatex_bibstyle;
 			delim = ",";
-		} else {
+		} else if (!chicago) {
 			if (!biblatex_bibstyle.empty()) {
 				opts = "bibstyle=" + biblatex_bibstyle;
 				delim = ",";
@@ -2392,7 +2398,10 @@ bool BufferParams::writeLaTeX(otexstream & os, LaTeXFeatures & features,
 			opts += delim + biblio_opts;
 		if (!opts.empty())
 			os << "[" << opts << "]";
-		os << "{biblatex}\n";
+		if (chicago)
+			os << "{biblatex-chicago}\n";
+		else
+			os << "{biblatex}\n";
 	}