block screen change when edge is occupied

--unfortunately this contains also white spaces
fixes. Sorry for this but by implementing multi-screen
the laptop wasnt correctly configured for
astyle and whitespaces

app/dockcorona.cpp

@@ -246,6 +246,7 @@ void DockCorona::addOutput(QScreen *screen)
     Q_ASSERT(screen);
 
     int id = m_screenPool->id(screen->name());
+
     if (id == -1) {
         int newId = m_screenPool->firstAvailableId();
         m_screenPool->insertScreenMapping(newId, screen->name());
@@ -282,6 +283,7 @@ void DockCorona::screenCountChangedTimer()
 
     qDebug() << "adding consideration....";
     qDebug() << "dock view running : " << m_dockViews.count();
+
     foreach (auto scr, qGuiApp->screens()) {
         qDebug() << "Found screen: " << scr->name();
 
@@ -302,8 +304,10 @@ void DockCorona::screenCountChangedTimer()
     }
 
     qDebug() << "removing consideration & updating screen for always on primary docks....";
+
     foreach (auto view, m_dockViews) {
         bool found{false};
+
         foreach (auto scr, qGuiApp->screens()) {
             int id = view->containment()->screen();
 
@@ -375,6 +379,21 @@ void DockCorona::aboutApplication()
     aboutDialog->show();
 }
 
+QList<Plasma::Types::Location> DockCorona::freeEdges(QScreen *screen) const
+{
+    using Plasma::Types;
+    QList<Types::Location> edges{Types::BottomEdge, Types::LeftEdge,
+                                 Types::TopEdge, Types::RightEdge};
+
+    for (auto *view : m_dockViews) {
+        if (view && view->currentScreen() == screen->name()) {
+            edges.removeOne(view->location());
+        }
+    }
+
+    return edges;
+}
+
 QList<Plasma::Types::Location> DockCorona::freeEdges(int screen) const
 {
     using Plasma::Types;
@@ -475,6 +494,7 @@ void DockCorona::addDock(Plasma::Containment *containment)
         QString connector = m_screenPool->connector(id);
         qDebug() << "add dock - connector : " << connector;
         bool found{false};
+
         foreach (auto scr, qGuiApp->screens()) {
             if (scr && scr->name() == connector) {
                 found = true;

app/dockcorona.h

@@ -55,6 +55,7 @@ public:
     QRect availableScreenRect(int id) const override;
 
     QList<Plasma::Types::Location> freeEdges(int screen) const;
+    QList<Plasma::Types::Location> freeEdges(QScreen *screen) const;
 
     int docksCount(int screen) const;
     int screenForContainment(const Plasma::Containment *containment) const override;

app/dockview.cpp

@@ -153,24 +153,39 @@ void DockView::init()
     qDebug() << "SOURCE:" << source();
 }
 
-void DockView::setCurrentScreen(const QString id)
+bool DockView::setCurrentScreen(const QString id)
 {
     if (!m_screenToFollow || m_screenToFollow->name() == id) {
-        return;
+        return false;
     }
 
-    QScreen *nextScreen{nullptr};
+    QScreen *nextScreen{qGuiApp->primaryScreen()};
 
+    if (id != "primary") {
         foreach (auto scr, qGuiApp->screens()) {
             if (scr && scr->name() == id) {
                 nextScreen = scr;
                 break;
             }
         }
+    }
+
+    if (nextScreen) {
+        auto *dockCorona = qobject_cast<DockCorona *>(this->corona());
+
+        if (dockCorona) {
+            auto freeEdges = dockCorona->freeEdges(nextScreen);
 
-    if (nextScreen)
+            if (!freeEdges.contains(location())) {
+                return false;
+            } else {
                 setScreenToFollow(nextScreen);
             }
+        }
+    }
+
+    return false;
+}
 
 void DockView::setScreenToFollow(QScreen *screen)
 {

app/dockview.h

@@ -130,7 +130,7 @@ public slots:
     Q_INVOKABLE QList<int> freeEdges() const;
     Q_INVOKABLE QVariantList containmentActions();
     Q_INVOKABLE void setLocalDockGeometry(const QRect &geometry);
-    Q_INVOKABLE void setCurrentScreen(const QString id);
+    Q_INVOKABLE bool setCurrentScreen(const QString id);
     Q_INVOKABLE bool tasksPresent();
     Q_INVOKABLE void updateEnabledBorders();
 

shell/contents/configuration/BehaviorConfig.qml

@@ -99,14 +99,43 @@ PlasmaComponents.Page {
                     Layout.fillWidth: true
                     Component.onCompleted: screenRow.updateScreens();
 
+                    //they are used to restore the index when the screen edge
+                    //is occuppied
+                    property bool acceptedIndex: true
+                    property int previousIndex: -1
+
+                    onCurrentIndexChanged: {
+                        //it is used to restore the index when the screen edge
+                        //is occuppied
+                        if (!acceptedIndex) {
+                            acceptedIndex = true;
+                            currentIndex = previousIndex;
+                        }
+                    }
+
                     onActivated: {
+                        previousIndex = currentIndex;
                         if (index === 0) {
+                            var succeed = dock.setCurrentScreen("primary");
+
+                            if (succeed) {
                                 dock.onPrimary = true;
+                            } else {
+                                console.log("the edge is already occupied!!!");
+                                acceptedIndex = false;
+                            }
                         } else if (index>0 && (index !== find(dock.currentScreen) || dock.onPrimary)) {
                             console.log("current index changed!!! :"+ index);
                             console.log("screen must be changed...");
+
+                            var succeed = dock.setCurrentScreen(textAt(index));
+
+                            if(succeed) {
                                dock.onPrimary = false;
-                            dock.setCurrentScreen(textAt(index));
+                            } else {
+                               console.log("the edge is already occupied!!!");
+                               acceptedIndex = false;
+                            }
                         }
                     }
                 }