From a5cc76216e08481a6f3614574a8ee498e5800afa Mon Sep 17 00:00:00 2001
From: Sam Varshavchik
Date: Sun, 6 Dec 2020 22:35:33 -0500
Subject: courier-unicode: partial logical reordering.

---
 unicode/biditest2.C          |  6 +++++-
 unicode/book.xml             | 14 ++++++++++----
 unicode/courier-unicode.h.in |  8 ++++++--
 unicode/unicodecpp.C         | 29 ++++++++++++++++++++++-------
 4 files changed, 43 insertions(+), 14 deletions(-)

diff --git a/unicode/biditest2.C b/unicode/biditest2.C
index cbd8c25..ce293b6 100644
--- a/unicode/biditest2.C
+++ b/unicode/biditest2.C
@@ -349,7 +349,11 @@ void character_test()
 
 			unicode::bidi_logical_order(logical_string,
 						    logical_levels,
-						    paragraph);
+						    paragraph,
+						    []
+						    (size_t, size_t) {},
+						    0,
+						    logical_string.size());
 
 			auto new_string=unicode::bidi_embed(logical_string,
 							    logical_levels,
diff --git a/unicode/book.xml b/unicode/book.xml
index 45686dc..3eb0a6e 100644
--- a/unicode/book.xml
+++ b/unicode/book.xml
@@ -2878,14 +2878,18 @@ See COPYING for distribution information.
 	      <paramdef>std::u32string &amp;<parameter>string</parameter></paramdef>
 	      <paramdef>std::vector &lt;unicode_bidi_level_t&gt; &amp;<parameter>levels</parameter></paramdef>
 	      <paramdef>unicode_bidi_level_t <parameter>paragraph_embedding</parameter></paramdef>
-	      <paramdef>const std::function&lt;void (size_t, size_t) noexcept&gt; &amp;<parameter>removed_callback</parameter></paramdef>
+	      <paramdef>const std::function&lt;void (size_t, size_t) noexcept&gt; &amp;<parameter>reorder_callback</parameter>=[](size_t, size_t){}</paramdef>
+	      <paramdef>size_t <parameter>starting_pos</parameter>=0</paramdef>
+	      <paramdef>size_t <parameter>n</parameter>=(size_t)-1</paramdef>
             </funcprototype>
 
 	    <funcprototype>
               <funcdef>void <function>unicode::bidi_logical_order</function></funcdef>
 	      <paramdef>std::vector &lt;unicode_bidi_level_t&gt; &amp;<parameter>levels</parameter></paramdef>
 	      <paramdef>unicode_bidi_level_t <parameter>paragraph_embedding</parameter></paramdef>
-	      <paramdef>const std::function&lt;void (size_t, size_t) noexcept&gt; &amp;<parameter>removed_callback</parameter></paramdef>
+	      <paramdef>const std::function&lt;void (size_t, size_t) noexcept&gt; &amp;<parameter>reorder_callback</parameter></paramdef>
+	      <paramdef>size_t <parameter>starting_pos</parameter>=0</paramdef>
+	      <paramdef>size_t <parameter>n</parameter>=(size_t)-1</paramdef>
             </funcprototype>
 
 	    <funcprototype>
@@ -3043,8 +3047,10 @@ auto [levels, level]=unicode::bidi_calc(types);
 
 	    <listitem>
 	      <para>
-		<function>unicode::bidi_reorder</function> and
-		<function>unicode::bidi_cleanup</function> take two optional
+		<function>unicode::bidi_reorder</function>,
+		<function>unicode::bidi_cleanup</function>, and
+		<function>unicode::bidi_logical_order</function>
+		take two optional
 		parameters (defaulted values or overloaded) specifying
 		an optional starting position and number of characters that
 		define a subset of the original string that gets reordered
diff --git a/unicode/courier-unicode.h.in b/unicode/courier-unicode.h.in
index 4bc7b55..9d398ec 100644
--- a/unicode/courier-unicode.h.in
+++ b/unicode/courier-unicode.h.in
@@ -2291,12 +2291,16 @@ int bidi_logical_order(std::u32string &string,
 		       std::vector<unicode_bidi_level_t> &levels,
 		       unicode_bidi_level_t paragraph_embedding,
 		       const std::function<void (size_t, size_t)>
-		       &lambda=[](size_t,size_t){});
+		       &lambda=[](size_t,size_t){},
+		       size_t starting_pos=0,
+		       size_t n=(size_t)-1);
 
 //! Convert Unicode string from canonical rendering order to logical order.
 void bidi_logical_order(std::vector<unicode_bidi_level_t> &levels,
 			unicode_bidi_level_t paragraph_embedding,
-			const std::function<void (size_t, size_t)> &lambda);
+			const std::function<void (size_t, size_t)> &lambda,
+			size_t starting_pos=0,
+			size_t n=(size_t)-1);
 
 //! Embed directional and isolation markers
 
diff --git a/unicode/unicodecpp.C b/unicode/unicodecpp.C
index 5677b86..3ef3b05 100644
--- a/unicode/unicodecpp.C
+++ b/unicode/unicodecpp.C
@@ -806,16 +806,24 @@ int unicode::bidi_logical_order(std::u32string &string,
 				std::vector<unicode_bidi_level_t> &levels,
 				unicode_bidi_level_t paragraph_embedding,
 				const std::function<void (size_t, size_t)>
-				&lambda)
+				&lambda,
+				size_t starting_pos,
+				size_t n)
 {
-	if (string.size() != levels.size())
+	auto s=string.size();
+
+	if (s != levels.size())
 		return -1;
 
-	if (string.empty())
+	if (starting_pos >= s)
 		return 0;
 
+	if (n > s-starting_pos)
+		n=s-starting_pos;
+
 	cb_wrapper<void (size_t, size_t)> cb{lambda};
-	unicode_bidi_logical_order(&string[0], &levels[0], string.size(),
+	unicode_bidi_logical_order(&string[starting_pos],
+				   &levels[starting_pos], n,
 				   paragraph_embedding,
 				   &reorder_callback,
 				   reinterpret_cast<void *>(&cb));
@@ -826,13 +834,20 @@ int unicode::bidi_logical_order(std::u32string &string,
 void unicode::bidi_logical_order(std::vector<unicode_bidi_level_t> &levels,
 				 unicode_bidi_level_t paragraph_embedding,
 				 const std::function<void (size_t, size_t)>
-				 &lambda)
+				 &lambda,
+				 size_t starting_pos,
+				 size_t n)
 {
-	if (levels.size() == 0)
+	auto s=levels.size();
+
+	if (starting_pos >= s)
 		return;
 
+	if (n > s-starting_pos)
+		n=s-starting_pos;
+
 	cb_wrapper<void (size_t, size_t)> cb{lambda};
-	unicode_bidi_logical_order(NULL, &levels[0], levels.size(),
+	unicode_bidi_logical_order(NULL, &levels[starting_pos], n,
 				   paragraph_embedding,
 				   &reorder_callback,
 				   reinterpret_cast<void *>(&cb));
-- 
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