From 1145e3d5cd58397812941712170975641a74ba8a Mon Sep 17 00:00:00 2001
From: Jinhao <cnjinhao@hotmail.com>
Date: Tue, 28 Aug 2018 07:31:05 +0800
Subject: [PATCH] fix crash that occurs when rendering an empty label(#333)

---
 source/gui/widgets/label.cpp | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/source/gui/widgets/label.cpp b/source/gui/widgets/label.cpp
index 013b5605..26be5a95 100644
--- a/source/gui/widgets/label.cpp
+++ b/source/gui/widgets/label.cpp
@@ -351,6 +351,22 @@ namespace nana
 				 */
 				unsigned _m_prepare_visual_lines(graph_reference graph, dstream::linecontainer& line, unsigned def_line_px, render_status& rs)
 				{
+					if (line.empty())
+					{
+						//Insert an empty visual line for empty content.
+#ifdef _nana_std_has_emplace_return_type
+						auto & vsline = rs.vslines.emplace_back();
+#else
+						rs.vslines.emplace_back();
+						auto & vsline = rs.vslines.back();
+
+						vsline.baseline = 0;
+						vsline.extent_height_px = def_line_px;
+						vsline.x_base = 0;
+#endif
+						return 0;
+					}
+
 					unsigned abs_text_px = 0;
 					unsigned max_ascent = 0;
 					unsigned max_descent = 0;