From 7686af1ba87f006198ed09c067e313d160565c08 Mon Sep 17 00:00:00 2001
From: Jean-Marc Lasgouttes <lasgouttes@lyx.org>
Date: Tue, 14 May 2019 22:44:29 +0200
Subject: [PATCH] Some Asian langagues allow to wrap text at any position

This is hardcoded for now for simplicity and to allow backporting to
2.3.

The behavior is unchanged for all languages but Chinese, Japanese or
Korean.

Fixes part of bug #10299.

(cherry picked from commit 26c2811cc474f7e3be953f73bf6e9d79f14022cd)
---
 src/Row.cpp | 23 +++++++++++++++++++++--
 status.23x  |  3 +++
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/src/Row.cpp b/src/Row.cpp
index 3fb87bd7e1..b241194e6e 100644
--- a/src/Row.cpp
+++ b/src/Row.cpp
@@ -19,6 +19,7 @@
 #include "Row.h"
 
 #include "DocIterator.h"
+#include "Language.h"
 
 #include "frontends/FontMetrics.h"
 
@@ -473,7 +474,25 @@ bool Row::shortenIfNeeded(pos_type const keep, int const w, int const next_width
 		// make a copy of the element to work on it.
 		Element brk = *cit_brk;
 		wid_brk -= brk.dim.wid;
-		if (brk.countSeparators() == 0 || brk.pos < keep)
+		/*
+		 * Some Asian languages split lines anywhere (no notion of
+		 * word). It seems that QTextLayout is not aware of this fact.
+		 * See for reference:
+		 *    https://en.wikipedia.org/wiki/Line_breaking_rules_in_East_Asian_languages
+		 *
+		 * FIXME: Something shall be done about characters which are
+		 * not allowed at the beginning or end of line.
+		 *
+		 * FIXME: hardcoding languages is bad. Put this information in
+		 * `languages' file.
+		*/
+		string const lang = brk.font.language()->lang();
+		bool force = lang == "chinese-simplified"
+		             || lang == "chinese-traditional"
+		             || lang == "japanese"
+		             || lang == "korean";
+		// FIXME: is it important to check for separators?
+		if ((!force && brk.countSeparators() == 0) || brk.pos < keep)
 			continue;
 		/* We have found a suitable separable element. This is the common case.
 		 * Try to break it cleanly (at word boundary) at a length that is both
@@ -481,7 +500,7 @@ bool Row::shortenIfNeeded(pos_type const keep, int const w, int const next_width
 		 * - shorter than the natural width of the element, in order to enforce
 		 *   break-up.
 		 */
-		if (brk.breakAt(min(w - wid_brk, brk.dim.wid - 2), false)) {
+		if (brk.breakAt(min(w - wid_brk, brk.dim.wid - 2), force)) {
 			/* if this element originally did not cause a row overflow
 			 * in itself, and the remainder of the row would still be
 			 * too large after breaking, then we will have issues in
diff --git a/status.23x b/status.23x
index 56a4c843c4..be847581ea 100644
--- a/status.23x
+++ b/status.23x
@@ -61,6 +61,9 @@ What's new
 
 - Improve some icons (bug 11476).
 
+- Improve line breaking of Chinese, Japanese and Korean text. There are still
+  issues, though (bug 10299).
+
 
 * DOCUMENTATION AND LOCALIZATION
 
-- 
2.39.5