Fix terminal display jumping to bottom of screen when trying to scroll up with the scrollbar already at the top. Spotted by Matthew Woehlke.

svn path=/trunk/KDE/kdebase/apps/konsole/; revision=792354

src/TerminalDisplay.cpp

@@ -2123,13 +2123,6 @@ void TerminalDisplay::mouseDoubleClickEvent(QMouseEvent* ev)
                      SLOT(tripleClickTimeout()));
 }
 
-bool TerminalDisplay::canScroll() const
-{
-	bool sliderAtTop = _scrollBar->value() == 0;
-	bool sliderAtBottom = _scrollBar->value() + _scrollBar->pageStep() >= _scrollBar->maximum();
-
-	return !(sliderAtTop && sliderAtBottom);
-}
 void TerminalDisplay::wheelEvent( QWheelEvent* ev )
 {
   if (ev->orientation() != Qt::Vertical)
@@ -2141,7 +2134,8 @@ void TerminalDisplay::wheelEvent( QWheelEvent* ev )
   // for the benefit of programs such as 'less'
   if ( _mouseMarks )
   {
-  	if (canScroll())
+	bool canScroll = _scrollBar->maximum() > 0;
+  	if (canScroll)
     	_scrollBar->event(ev);
 	else
 	{

src/TerminalDisplay.h

@@ -649,9 +649,6 @@ private:
 	// redraws the cursor
 	void updateCursor();
 
-	// returns true if the scroll bar thumb could be moved
-	bool canScroll() const;
-
     // the window onto the terminal screen which this display
     // is currently showing.  
     QPointer<ScreenWindow> _screenWindow;