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List:       kde-commits
Subject:    KDE/kdelibs/khtml/rendering
From:       Germain Garand <germain () ebooksfrance ! org>
Date:       2009-03-14 4:35:34
Message-ID: 1237005334.183569.14944.nullmailer () svn ! kde ! org
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SVN commit 939171 by ggarand:

rework the algorithm that avoids endless scrollbar cycles.

there were several mistakes made during Qt4 porting, which in turn made
direct layer translation often trigger pathological scrollbar flicker
(e.g. when moving some dhtml positioned boxes)


 M  +34 -22    render_canvas.cpp  


--- trunk/KDE/kdelibs/khtml/rendering/render_canvas.cpp #939170:939171
@@ -4,7 +4,7 @@
  * Copyright (C) 1999-2003 Lars Knoll (knoll@kde.org)
  *           (C) 2003 Apple Computer, Inc.
  *           (C) 2005 Allan Sandfeld Jensen (kde@carewolf.com)
- *           (C) 2007-2008 Germain Garand (germain@ebooksfrance.org)
+ *           (C) 2007-2009 Germain Garand (germain@ebooksfrance.org)
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Library General Public
@@ -232,41 +232,53 @@
 
     if (!m_pagedMode && m_view) {
 
+        // we need to adjust the document's size to make sure we don't enter
+        // an endless cycle of scrollbars being added, then removed at the next layout.
+
         bool vss = m_view->verticalScrollBar()->isVisible();
         bool hss = m_view->horizontalScrollBar()->isVisible();
-        QSize s = m_view->maximumViewportSize();
 
-        int zoomedDocWidth = m_cachedDocWidth*zLevel/100;
-        int zoomedDocHeight = m_cachedDocHeight*zLevel/100;
-        if ( zoomedDocWidth > s.width() )
-            s.setWidth( s.width()-m_view->verticalScrollBar()->sizeHint().width() );
-        if ( zoomedDocHeight > s.height() )
-            s.setHeight( s.height()-m_view->horizontalScrollBar()->sizeHint().height() );
-   
+        // calculate the extent of scrollbars
+        int vsPixSize = m_view->verticalScrollBar()->sizeHint().width();
+        int hsPixSize = m_view->horizontalScrollBar()->sizeHint().height();
+
+        // this variable holds the size the viewport will have after the inner content is resized to
+        // the new document dimensions
+        QSize viewport = m_view->maximumViewportSize();
+
+        // of course, if the scrollbar policy isn't auto, there's no point adjusting any value..
+        int overrideH = m_view->verticalScrollBarPolicy() == Qt::ScrollBarAsNeeded ? 0 : hDocH;
+        int overrideW = m_view->verticalScrollBarPolicy() == Qt::ScrollBarAsNeeded ? 0 : hDocW;
+        
+        if ( !overrideW && hDocW > viewport.width() )
+            viewport.setHeight( viewport.height() - hsPixSize );
+        if ( !overrideH && hDocH > viewport.height() )
+            viewport.setWidth( viewport.width() - vsPixSize );
+            
         // if we are about to show a scrollbar, and the document is sized to the viewport w or h,
         // then reserve the scrollbar space so that it doesn't trigger the _other_ scrollbar
 
-        if (!vss && m_width - m_view->verticalScrollBar()->sizeHint().width() == s.width() &&
-            zoomedDocWidth <= m_width)
-            hDocW = qMin( zoomedDocWidth, s.width() );
+        if (!vss && m_width - vsPixSize == viewport.width() &&
+            hDocW <= m_width)
+            hDocW = qMin( hDocW, viewport.width() );
 
-        if (!hss && m_height - m_view->horizontalScrollBar()->sizeHint().height() == s.height() &&
-            zoomedDocHeight <= m_height)
-            hDocH = qMin( zoomedDocHeight, s.height() );
+        if (!hss && m_height - hsPixSize == viewport.height() &&
+            hDocH <= m_height)
+            hDocH = qMin( hDocH, viewport.height() );
 
         // likewise, if a scrollbar is shown, and we have a cunning plan to turn it off,
         // think again if we are falling downright in the hysteresis zone
 
-        if (vss && s.width() > zoomedDocWidth && zoomedDocWidth > m_view->visibleWidth())
-            hDocW = s.width()+1;
+        if (vss && viewport.width() > hDocW && hDocW > m_view->visibleWidth())
+            hDocW = viewport.width()+1;
 
-        if (hss && s.height() > zoomedDocHeight && zoomedDocHeight > m_view->visibleHeight())
-            hDocH = s.height()+1;
+        if (hss && viewport.height() > hDocH && hDocH > m_view->visibleHeight())
+            hDocH = viewport.height()+1;
 
-        m_view->resizeContents(hDocW, hDocH);
+        m_view->resizeContents((overrideW ? overrideW : hDocW), (overrideH ? overrideH : hDocH));
 
-        setWidth( m_viewportWidth = s.width() );
-        setHeight( m_viewportHeight = s.height() );
+        setWidth( m_viewportWidth = (overrideW ? m_view->visibleWidth() : viewport.width()) );
+        setHeight( m_viewportHeight = (overrideH ? m_view->visibleHeight() : viewport.height()) );
     }
     layer()->resize( qMax( m_cachedDocWidth,int( m_width ) ), qMax( m_cachedDocHeight,m_height ) );
 }
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