From 8a3a9a40cb071ca001f79e0192e0934e19628bd1 Mon Sep 17 00:00:00 2001
From: Yen Chi Hsuan <yan12125@gmail.com>
Date: Sat, 28 Oct 2017 03:51:33 +0800
Subject: [PATCH] Fix behavior of scroll up (SU)

This is a backport of https://github.com/KDE/konsole/commit/7ff23512fd6c6af1dba87083446f85baf75e9c71
---
 lib/Screen.cpp | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/lib/Screen.cpp b/lib/Screen.cpp
index 6104764..676d2a7 100644
--- a/lib/Screen.cpp
+++ b/lib/Screen.cpp
@@ -751,13 +751,18 @@ QRect Screen::lastScrolledRegion() const
 
 void Screen::scrollUp(int from, int n)
 {
-    if (n <= 0 || from + n > _bottomMargin) return;
+    if (n <= 0)
+        return;
+    if (from > _bottomMargin)
+        return;
+    if (from + n > _bottomMargin)
+        n = _bottomMargin + 1 - from;
 
     _scrolledLines -= n;
     _lastScrolledRegion = QRect(0,_topMargin,columns-1,(_bottomMargin-_topMargin));
 
     //FIXME: make sure `topMargin', `bottomMargin', `from', `n' is in bounds.
-    moveImage(loc(0,from),loc(0,from+n),loc(columns-1,_bottomMargin));
+    moveImage(loc(0,from),loc(0,from+n),loc(columns,_bottomMargin));
     clearImage(loc(0,_bottomMargin-n+1),loc(columns-1,_bottomMargin),' ');
 }