From bc5da29e9c73be42b55bf0761ab80d52c8487c2b Mon Sep 17 00:00:00 2001
From: =?utf8?q?Stefan=20K=C3=BCng?= <stefankueng@gmail.com>
Date: Mon, 27 Dec 2021 11:52:46 +0100
Subject: [PATCH] Calculate the char width when wrapping using real text
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(fixes issue #3799)

Signed-off-by: Stefan Küng <stefankueng@gmail.com>
Signed-off-by: Sven Strickroth <email@cs-ware.de>
---
 src/Changelog.txt              |  1 +
 src/TortoiseMerge/BaseView.cpp | 35 ++++++++++++++++++++++++++++++++---
 2 files changed, 33 insertions(+), 3 deletions(-)

diff --git a/src/Changelog.txt b/src/Changelog.txt
index 608a503ed..dd4fa950c 100644
--- a/src/Changelog.txt
+++ b/src/Changelog.txt
@@ -33,6 +33,7 @@ Released: unreleased
  * Fixes issue #3826: Help links to TortoiseGit site don't open in a sensible browser
  * Fixed issue #3815: TortoiseGitMerge crashes on Windows 7 on startup when winrt libraries are installed
  * Fixed issue #3831: TortoiseGitMerge omits text after null byte when word wrap is enabled
+ * Fixed issue #3799: Display of Long lines with Chinese characters is truncated in TortoiseGitMerge dialog
 
 = Release 2.12.0 =
 Released: 2021-03-31
diff --git a/src/TortoiseMerge/BaseView.cpp b/src/TortoiseMerge/BaseView.cpp
index 1680a3749..40afb829b 100644
--- a/src/TortoiseMerge/BaseView.cpp
+++ b/src/TortoiseMerge/BaseView.cpp
@@ -4899,12 +4899,41 @@ int CBaseView::CountMultiLines( int nViewLine )
 	auto multiLines = CStringUtils::WordWrap(m_pViewData->GetLine(nViewLine), GetScreenChars() - 1, GetTabSize());
 
 	TScreenedViewLine oScreenedLine;
+	bool subLinesSet = true;
+	if (m_pMainFrame->m_bWrapLines)
+	{
+		CDC* pDC = GetDC();
+		CFont* pOldFont = pDC->SelectObject(GetFont());
 
-	for (const auto& line : multiLines)
+		for (const auto& line : multiLines)
+		{
+			if (line.GetLength())
+			{
+				// we use the 'X' char to determine the char width,
+				// but e.g. chinese chars are much wider. To make sure
+				// that we wrap correctly, we calculate the average char width
+				// here by using the real line text
+				const CSize szCharExt = pDC->GetTextExtent(line);
+				if (szCharExt.cx / line.GetLength() > m_nCharWidth)
+				{
+					m_nCharWidth = szCharExt.cx / line.GetLength();
+					subLinesSet = false;
+				}
+			}
+			oScreenedLine.SubLines.push_back(line);
+		}
+		pDC->SelectObject(pOldFont);
+		ReleaseDC(pDC);
+	}
+	else
 	{
-		oScreenedLine.SubLines.push_back(line);
+		for (const auto& line : multiLines)
+		{
+			oScreenedLine.SubLines.push_back(line);
+		}
 	}
-	oScreenedLine.bSublinesSet = true;
+
+	oScreenedLine.bSublinesSet = subLinesSet;
 	m_ScreenedViewLine[nViewLine] = oScreenedLine;
 
 	return CountMultiLines(nViewLine);
-- 
2.11.4.GIT