Guard every remaining access to rootInfo

Summary:
For a future XFree KWin. Only remaining not guarded usages are in
Workspace::init, but that one needs to be refactored anyway for
becoming X free.

Test Plan: Compiles

Reviewers: #kwin, #plasma

Subscribers: plasma-devel, kwin

Tags: #kwin

Differential Revision: https://phabricator.kde.org/D7173

geometry.cpp

@@ -70,10 +70,12 @@ extern bool is_multihead;
 void Workspace::desktopResized()
 {
     QRect geom = screens()->geometry();
-    NETSize desktop_geometry;
-    desktop_geometry.width = geom.width();
-    desktop_geometry.height = geom.height();
-    rootInfo()->setDesktopGeometry(desktop_geometry);
+    if (rootInfo()) {
+        NETSize desktop_geometry;
+        desktop_geometry.width = geom.width();
+        desktop_geometry.height = geom.height();
+        rootInfo()->setDesktopGeometry(desktop_geometry);
+    }
 
     updateClientArea();
     saveOldScreenSizes(); // after updateClientArea(), so that one still uses the previous one
@@ -309,13 +311,15 @@ void Workspace::updateClientArea(bool force)
         oldrestrictedmovearea = restrictedmovearea;
         restrictedmovearea = new_rmoveareas;
         screenarea = new_sareas;
-        NETRect r;
-        for (int i = 1; i <= numberOfDesktops; i++) {
-            r.pos.x = workarea[ i ].x();
-            r.pos.y = workarea[ i ].y();
-            r.size.width = workarea[ i ].width();
-            r.size.height = workarea[ i ].height();
-            rootInfo()->setWorkArea(i, r);
+        if (rootInfo()) {
+            NETRect r;
+            for (int i = 1; i <= numberOfDesktops; i++) {
+                r.pos.x = workarea[ i ].x();
+                r.pos.y = workarea[ i ].y();
+                r.size.width = workarea[ i ].width();
+                r.size.height = workarea[ i ].height();
+                rootInfo()->setWorkArea(i, r);
+            }
         }
 
         for (auto it = m_allClients.constBegin();

layers.cpp

@@ -151,6 +151,9 @@ void Workspace::updateStackingOrder(bool propagate_new_clients)
  */
 void Workspace::stackScreenEdgesUnderOverrideRedirect()
 {
+    if (!rootInfo()) {
+        return;
+    }
     Xcb::restackWindows(QVector<xcb_window_t>() << rootInfo()->supportWindow() << ScreenEdges::self()->windows());
 }
 
@@ -160,6 +163,9 @@ void Workspace::stackScreenEdgesUnderOverrideRedirect()
  */
 void Workspace::propagateClients(bool propagate_new_clients)
 {
+    if (!rootInfo()) {
+        return;
+    }
     // restack the windows according to the stacking order
     // supportWindow > electric borders > clients > hidden clients
     QVector<xcb_window_t> newWindowStack;

workspace.cpp

@@ -948,7 +948,9 @@ void Workspace::updateClientVisibilityOnDesktopChange(uint oldDesktop, uint newD
         }
     }
     // Now propagate the change, after hiding, before showing
-    rootInfo()->setCurrentDesktop(VirtualDesktopManager::self()->current());
+    if (rootInfo()) {
+        rootInfo()->setCurrentDesktop(VirtualDesktopManager::self()->current());
+    }
 
     if (movingClient && !movingClient->isOnDesktop(newDesktop)) {
         movingClient->setDesktop(newDesktop);
@@ -1246,7 +1248,9 @@ void Workspace::sendClientToScreen(AbstractClient* c, int screen)
 
 void Workspace::sendPingToWindow(xcb_window_t window, xcb_timestamp_t timestamp)
 {
-    rootInfo()->sendPing(window, timestamp);
+    if (rootInfo()) {
+        rootInfo()->sendPing(window, timestamp);
+    }
 }
 
 /**