Added reset methods to WindowMotionManager.

Fixed bug in present windows when if there is only one window on a Xinerama screen it is zoomed into nothingness when using the natural layout.
CCBUG: 171812

svn path=/trunk/KDE/kdebase/workspace/; revision=865798

effects/presentwindows.cpp

@@ -730,6 +730,13 @@ void PresentWindowsEffect::calculateWindowTransformationsKompose( EffectWindowLi
 
 void PresentWindowsEffect::calculateWindowTransformationsNatural( EffectWindowList windowlist, int screen )
     {
+    if( windowlist.count() == 1 )
+        { // No idea why this is needed but if there is only one window on a Xinerama screen
+          // then the window is scaled into nothingness at (0,0) if its position isn't reset.
+        m_motionManager.reset( windowlist[0] );
+        return;
+        }
+
     // As we are using pseudo-random movement (See "slot") we need to make sure the list
     // is always sorted the same way no matter which window is currently active.
     qSort( windowlist );

lib/kwineffects.cpp

@@ -1153,6 +1153,34 @@ void WindowMotionManager::calculate( int time )
         }
     }
 
+void WindowMotionManager::reset()
+    {
+    if( !m_managedWindows.count() )
+        return;
+
+    EffectWindowList windows = m_managedWindows.keys();
+
+    for( int i = 0; i < windows.size(); i++ )
+        {
+        EffectWindow *w = windows.at( i );
+        m_managedWindows[ w ].translation.setTarget( w->pos() );
+        m_managedWindows[ w ].translation.finish();
+        m_managedWindows[ w ].scale.setTarget( QPointF( 1.0, 1.0 ));
+        m_managedWindows[ w ].scale.finish();
+        }
+    }
+
+void WindowMotionManager::reset( EffectWindow *w )
+    {
+    if( !m_managedWindows.contains( w ))
+        return;
+
+    m_managedWindows[ w ].translation.setTarget( w->pos() );
+    m_managedWindows[ w ].translation.finish();
+    m_managedWindows[ w ].scale.setTarget( QPointF( 1.0, 1.0 ));
+    m_managedWindows[ w ].scale.finish();
+    }
+
 void WindowMotionManager::apply( EffectWindow *w, WindowPaintData &data )
     {
     if( !m_managedWindows.contains( w ))

lib/kwineffects.h

@@ -1315,6 +1315,17 @@ class KWIN_EXPORT WindowMotionManager
          * WindowPrePaintData::setTransformed()
          */
         void apply( EffectWindow *w, WindowPaintData &data );
+        /**
+         * Set all motion targets and values back to where the
+         * windows were before transformations. The same as
+         * unmanaging then remanaging all windows.
+         */
+        void reset();
+        /**
+         * Resets the motion target and current value of a single
+         * window.
+         */
+        void reset( EffectWindow *w );
 
         /**
          * As the manager to move the window to the target position