fixes for multi-screen behavior

--fix wrong placement at multi-screen environment
during startup. freeEdges function was not sufficient for
reconsiderScreen() because there was a chance to
exclude edges that even though they were available
it returned fault results. Such case is when
a view request available edges for specific screen
and the edge of that specific view is also exluded
because that view has not finished its movement
to the new assigned screen.

--fix re-adding an explicit dock when its screen
is activated. A check was missing in order to
confirm that a primary dock is occuping that
edge but we must check also that the primary
screen is the same with the explicit one.

--add/improve debug messages

app/dock/dockview.cpp

@@ -516,7 +516,7 @@ void DockView::reconsiderScreen()
         QList<Types::Location> edges{Types::BottomEdge, Types::LeftEdge,
                                      Types::TopEdge, Types::RightEdge};
 
-        edges = m_managedLayout ? m_managedLayout->freeEdges(qGuiApp->primaryScreen()) : edges;
+        edges = m_managedLayout ? m_managedLayout->availableEdgesForView(qGuiApp->primaryScreen(), this) : edges;
 
         //change to primary screen only if the specific edge is free
         qDebug() << "updating the primary screen for dock...";
@@ -906,8 +906,15 @@ inline void DockView::syncGeometry()
     //! before updating the positioning and geometry of the dock
     //! we make sure that the dock is at the correct screen
     if (this->screen() != m_screenToFollow) {
-        qDebug() << "Sync Geometry screens inconsistent!!!!";
-        m_screenSyncTimer.start();
+        qDebug() << "Sync Geometry screens inconsistent!!!! ";
+
+        if (m_screenToFollow) {
+            qDebug() << "Sync Geometry screens inconsistent for m_screenToFollow:" << m_screenToFollow->name() << " dock screen:" << screen()->name();
+        }
+
+        if (!m_screenSyncTimer.isActive()) {
+            m_screenSyncTimer.start();
+        }
     } else {
         found = true;
     }
@@ -958,6 +965,8 @@ inline void DockView::syncGeometry()
         updateEnabledBorders();
         resizeWindow(availableScreenRect);
         updatePosition(availableScreenRect);
+
+        qDebug() << "syncGeometry() calculations for screen: " << screen()->name() << " _ " << screen()->geometry();
     }
 
     qDebug() << "syncGeometry() ended...";

app/layout.cpp

@@ -910,7 +910,9 @@ void Layout::addDock(Plasma::Containment *containment, bool forceOnPrimary, int
             return;
         }
 
-        if (primaryDockOccupyEdge(containment->location())) {
+        //! explicit dock can not be added at explicit screen when that screen is the same with
+        //! primary screen and that edge is already occupied by a primary dock
+        if (nextScreen == qGuiApp->primaryScreen() && primaryDockOccupyEdge(containment->location())) {
             qDebug() << "reject : adding explicit dock, primary dock occupies edge at screen ! : " << connector;
             return;
         }
@@ -1765,7 +1767,7 @@ bool Layout::dockViewExists(Plasma::Containment *containment)
     return m_dockViews.keys().contains(containment);
 }
 
-QList<Plasma::Types::Location> Layout::freeEdges(QScreen *screen) const
+QList<Plasma::Types::Location> Layout::availableEdgesForView(QScreen *scr, DockView *forView) const
 {
     using Plasma::Types;
     QList<Types::Location> edges{Types::BottomEdge, Types::LeftEdge,
@@ -1776,7 +1778,28 @@ QList<Plasma::Types::Location> Layout::freeEdges(QScreen *screen) const
     }
 
     foreach (auto view, m_dockViews) {
-        if (view && view->currentScreen() == screen->name()) {
+        //! make sure that availabe edges takes into account only views that should be excluded,
+        //! this is why the forView should not be excluded
+        if (view && view != forView && view->currentScreen() == scr->name()) {
+            edges.removeOne(view->location());
+        }
+    }
+
+    return edges;
+}
+
+QList<Plasma::Types::Location> Layout::freeEdges(QScreen *scr) const
+{
+    using Plasma::Types;
+    QList<Types::Location> edges{Types::BottomEdge, Types::LeftEdge,
+                                 Types::TopEdge, Types::RightEdge};
+
+    if (!m_corona) {
+        return edges;
+    }
+
+    foreach (auto view, m_dockViews) {
+        if (view && view->currentScreen() == scr->name()) {
             edges.removeOne(view->location());
         }
     }

app/layout.h

@@ -137,7 +137,11 @@ public:
     //! that dockView
     QList<Plasma::Containment *> unassignFromLayout(DockView *dockView);
 
-    QList<Plasma::Types::Location> freeEdges(QScreen *screen) const;
+    //! Available edges for specific view in that screen
+    QList<Plasma::Types::Location> availableEdgesForView(QScreen *scr, DockView *forView) const;
+
+    //! All free edges in that screen
+    QList<Plasma::Types::Location> freeEdges(QScreen *scr) const;
     QList<Plasma::Types::Location> freeEdges(int screen) const;
 
     //! make it only read-only