kwin: add new KWin::Compositor::starting() method and use it in during startup

I have a feeling even that will not be enough

Signed-off-by: Ivailo Monev <xakepa10@gmail.com>

kwin/composite.h

@@ -122,6 +122,14 @@ public:
     static bool compositing() {
         return s_compositor != NULL && s_compositor->isActive();
     }
+    /**
+     * @brief Static check to test whether the Compositor is still starting.
+     *
+     * @return bool @c true if there is a Compositor and it is still starting, @c false otherwise
+     **/
+    static bool starting() {
+        return s_compositor != NULL && s_compositor->m_starting;
+    }
 
     // for delayed supportproperty management of effects
     void keepSupportProperty(xcb_atom_t atom);

kwin/main.cpp

@@ -60,6 +60,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.
 #include "utils.h"
 #include "effects.h"
 #include "workspace.h"
+#include "composite.h"
 #include "xcbutils.h"
 
 #include <X11/Xproto.h>
@@ -488,7 +489,17 @@ int main(int argc, char * argv[])
         return 1;
     }
 
-    a.processEvents(); // trigger any events before resuming such as compositor setup
+    // wait for the workspace initialization to complete before resuming
+    while (KWin::Workspace::self() && KWin::Workspace::self()->initializing()) {
+        a.processEvents();
+    }
+    // and the compositor
+    while (KWin::Compositor::starting()) {
+        a.processEvents();
+    }
+    // and one more iteration just in case
+    a.processEvents();
+
     ksmserver.resumeStartup("kwin");
     KWin::SessionManager weAreIndeed;
     KWin::SessionSaveDoneHelper helper;