From de79549e8ff8a0c0798731d053e721337edf5e29 Mon Sep 17 00:00:00 2001
From: Robert Knight <robertknight@gmail.com>
Date: Fri, 1 Jun 2007 14:27:26 +0000
Subject: [PATCH] Prevent scrolling of views which are not following the latest
 output when new output is received from the terminal and the history is full.

svn path=/trunk/KDE/kdebase/apps/konsole/; revision=670451
---
 src/Emulation.cpp    |  1 +
 src/Screen.cpp       | 17 +++++++++++++++--
 src/Screen.h         | 19 +++++++++++++++++++
 src/ScreenWindow.cpp | 10 ++++++++++
 4 files changed, 45 insertions(+), 2 deletions(-)

diff --git a/src/Emulation.cpp b/src/Emulation.cpp
index 123e1ecbe..41199262d 100644
--- a/src/Emulation.cpp
+++ b/src/Emulation.cpp
@@ -435,6 +435,7 @@ void Emulation::showBulk()
     emit outputChanged();
 
     _currentScreen->resetScrolledLines();
+    _currentScreen->resetDroppedLines();
 }
 
 void Emulation::bufferedUpdate()
diff --git a/src/Screen.cpp b/src/Screen.cpp
index e485883f2..a15bb9286 100644
--- a/src/Screen.cpp
+++ b/src/Screen.cpp
@@ -69,6 +69,7 @@ Screen::Screen(int l, int c)
     columns(c),
     screenLines(new ImageLine[lines+1] ),
     _scrolledLines(0),
+    _droppedLines(0),
     hist(new HistoryScrollNone()),
     cuX(0), cuY(0),
     cu_re(0),
@@ -835,7 +836,14 @@ int Screen::scrolledLines() const
 {
         return _scrolledLines;
 }
-
+int Screen::droppedLines() const
+{
+    return _droppedLines;
+}
+void Screen::resetDroppedLines()
+{
+    _droppedLines = 0;
+}
 void Screen::resetScrolledLines()
 {
     //qDebug() << "scrolled lines reset";
@@ -1524,7 +1532,7 @@ QString Screen::getHistoryLine(int no)
 
 void Screen::addHistLine()
 {
-  // add to hist buffer
+  // add line to history buffer
   // we have to take care about scrolling, too...
 
   if (hasScroll())
@@ -1538,6 +1546,11 @@ void Screen::addHistLine()
 
     bool beginIsTL = (sel_begin == sel_TL);
 
+    // If the history is full, increment the count
+    // of dropped lines
+    if ( newHistLines == oldHistLines )
+        _droppedLines++;
+
     // Adjust selection for the new point of reference
     if (newHistLines > oldHistLines)
     {
diff --git a/src/Screen.h b/src/Screen.h
index 023b19aff..d7b3f1260 100644
--- a/src/Screen.h
+++ b/src/Screen.h
@@ -344,6 +344,23 @@ public: // these are all `Screen' operations
      */
     void resetScrolledLines();
 
+    /**
+     * Returns the number of lines of output which have been
+     * dropped from the history since the last call
+     * to resetDroppedLines()
+     *
+     * If the history is not unlimited then it will drop
+     * the oldest lines of output if new lines are added when
+     * it is full.  
+     */
+    int droppedLines() const;
+
+    /**
+     * Resets the count of the number of lines dropped from
+     * the history.
+     */
+    void resetDroppedLines();
+
 private: // helper
 
 	//copies a line of text from the screen or history into a stream using a specified character decoder
@@ -403,6 +420,8 @@ private: // helper
     int _scrolledLines;
     QRect _lastScrolledRegion;
 
+    int _droppedLines;
+
     QVarLengthArray<LineProperty,64> lineProperties;    
 	
     // history buffer ---------------
diff --git a/src/ScreenWindow.cpp b/src/ScreenWindow.cpp
index 4fcced14e..201bad062 100644
--- a/src/ScreenWindow.cpp
+++ b/src/ScreenWindow.cpp
@@ -217,6 +217,16 @@ void ScreenWindow::notifyOutputChanged()
         _scrollCount -= _screen->scrolledLines();
         _currentLine = _screen->getHistLines();
     }
+    else
+    {
+        // if the history is not unlimited then it may 
+        // have run out of space and dropped the oldest
+        // lines of output - in this case the screen
+        // window's current line number will need to 
+        // be adjusted - otherwise the output will scroll
+        _currentLine = qMax(0,_currentLine - 
+                              _screen->droppedLines());
+    }
 
     emit outputChanged(); 
 }