gtk3: listen to state-flags-changed and disable toplevels when in backdrop

Change-Id: I173618b2e6a2ad69918da8b85ec0eef7099f1d3d
(cherry picked from commit 02b1e147)

vcl/inc/unx/gtk/gtkframe.hxx

@@ -238,6 +238,7 @@ class GtkSalFrame : public SalFrame, public X11WindowProvider
     static void         signalStyleSet( GtkWidget*, GtkStyle* pPrevious, gpointer );
 #if GTK_CHECK_VERSION(3,0,0)
     static gboolean     signalDraw( GtkWidget*, cairo_t *cr, gpointer );
+    static void         signalFlagsChanged( GtkWidget*, GtkStateFlags, gpointer );
 #if GTK_CHECK_VERSION(3,14,0)
     static void         gestureSwipe(GtkGestureSwipe* gesture, gdouble velocity_x, gdouble velocity_y, gpointer frame);
     static void         gestureLongPress(GtkGestureLongPress* gesture, gpointer frame);
@@ -252,7 +253,7 @@ class GtkSalFrame : public SalFrame, public X11WindowProvider
     static gboolean     signalMotion( GtkWidget*, GdkEventMotion*, gpointer );
     static gboolean     signalKey( GtkWidget*, GdkEventKey*, gpointer );
     static gboolean     signalDelete( GtkWidget*, GdkEvent*, gpointer );
-    static gboolean     signalState( GtkWidget*, GdkEvent*, gpointer );
+    static gboolean     signalWindowState( GtkWidget*, GdkEvent*, gpointer );
     static gboolean     signalScroll( GtkWidget*, GdkEvent*, gpointer );
     static gboolean     signalCrossing( GtkWidget*, GdkEventCrossing*, gpointer );
     static gboolean     signalVisibility( GtkWidget*, GdkEventVisibility*, gpointer );

vcl/unx/gtk/window/gtksalframe.cxx

@@ -1036,6 +1036,7 @@ void GtkSalFrame::InitCommon()
     g_signal_connect( G_OBJECT(m_pWindow), "button-release-event", G_CALLBACK(signalButton), this );
 #if GTK_CHECK_VERSION(3,0,0)
     g_signal_connect( G_OBJECT(m_pWindow), "draw", G_CALLBACK(signalDraw), this );
+    g_signal_connect( G_OBJECT(m_pWindow), "state-flags-changed", G_CALLBACK(signalFlagsChanged), this );
 #if GTK_CHECK_VERSION(3,14,0)
     GtkGesture *pSwipe = gtk_gesture_swipe_new(m_pWindow);
     g_signal_connect(pSwipe, "swipe", G_CALLBACK(gestureSwipe), this);
@@ -1061,7 +1062,7 @@ void GtkSalFrame::InitCommon()
     g_signal_connect( G_OBJECT(m_pWindow), "key-press-event", G_CALLBACK(signalKey), this );
     g_signal_connect( G_OBJECT(m_pWindow), "key-release-event", G_CALLBACK(signalKey), this );
     g_signal_connect( G_OBJECT(m_pWindow), "delete-event", G_CALLBACK(signalDelete), this );
-    g_signal_connect( G_OBJECT(m_pWindow), "window-state-event", G_CALLBACK(signalState), this );
+    g_signal_connect( G_OBJECT(m_pWindow), "window-state-event", G_CALLBACK(signalWindowState), this );
     g_signal_connect( G_OBJECT(m_pWindow), "scroll-event", G_CALLBACK(signalScroll), this );
     g_signal_connect( G_OBJECT(m_pWindow), "leave-notify-event", G_CALLBACK(signalCrossing), this );
     g_signal_connect( G_OBJECT(m_pWindow), "enter-notify-event", G_CALLBACK(signalCrossing), this );
@@ -3439,6 +3440,24 @@ gboolean GtkSalFrame::signalButton( GtkWidget*, GdkEventButton* pEvent, gpointer
     return true;
 }
 
+#if GTK_CHECK_VERSION(3,0,0)
+void GtkSalFrame::signalFlagsChanged( GtkWidget* ,  GtkStateFlags state, gpointer frame )
+{
+    GtkSalFrame* pThis = static_cast<GtkSalFrame*>(frame);
+
+    bool bOldBackDrop = state & GTK_STATE_FLAG_BACKDROP;
+    bool bNewBackDrop = (gtk_widget_get_state_flags(GTK_WIDGET(pThis->m_pWindow)) & GTK_STATE_FLAG_BACKDROP);
+    if (bNewBackDrop && !bOldBackDrop)
+    {
+        pThis->GetWindow()->Disable();
+    }
+    else if (bOldBackDrop && !bNewBackDrop)
+    {
+        pThis->GetWindow()->Enable();
+    }
+}
+#endif
+
 gboolean GtkSalFrame::signalScroll( GtkWidget*, GdkEvent* pEvent, gpointer frame )
 {
     GtkSalFrame* pThis = static_cast<GtkSalFrame*>(frame);
@@ -4044,7 +4063,7 @@ void GtkSalFrame::signalStyleSet( GtkWidget*, GtkStyle* pPrevious, gpointer fram
 #endif
 }
 
-gboolean GtkSalFrame::signalState( GtkWidget*, GdkEvent* pEvent, gpointer frame )
+gboolean GtkSalFrame::signalWindowState( GtkWidget*, GdkEvent* pEvent, gpointer frame )
 {
     GtkSalFrame* pThis = static_cast<GtkSalFrame*>(frame);
     if( (pThis->m_nState & GDK_WINDOW_STATE_ICONIFIED) != (pEvent->window_state.new_window_state & GDK_WINDOW_STATE_ICONIFIED ) )