Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineView.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineView.cpp	(revision 54113)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineView.cpp	(revision 54114)
@@ -176,7 +176,11 @@
     const double dScaleFactor = gEDataManager->scaleFactor(vboxGlobal().managedVMUuid());
     frameBuffer()->setScaleFactor(dScaleFactor);
-    display().NotifyScaleFactorChange(m_uScreenId,
-                                      (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
-                                      (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+    /* Propagate scale-factor to 3D service if necessary: */
+    if (machine().GetAccelerate3DEnabled() && vboxGlobal().is3DAvailable())
+    {
+        display().NotifyScaleFactorChange(m_uScreenId,
+                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
+                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+    }
 
     /* Take unscaled HiDPI output mode into account: */
@@ -363,7 +367,11 @@
     const double dScaleFactor = gEDataManager->scaleFactor(vboxGlobal().managedVMUuid());
     frameBuffer()->setScaleFactor(dScaleFactor);
-    display().NotifyScaleFactorChange(m_uScreenId,
-                                      (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
-                                      (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+    /* Propagate scale-factor to 3D service if necessary: */
+    if (machine().GetAccelerate3DEnabled() && vboxGlobal().is3DAvailable())
+    {
+        display().NotifyScaleFactorChange(m_uScreenId,
+                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
+                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+    }
 
     /* Handle scale attributes change: */
@@ -548,7 +556,11 @@
         const double dScaleFactor = gEDataManager->scaleFactor(vboxGlobal().managedVMUuid());
         m_pFrameBuffer->setScaleFactor(dScaleFactor);
-        display().NotifyScaleFactorChange(m_uScreenId,
-                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
-                                          (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+        /* Propagate scale-factor to 3D service if necessary: */
+        if (machine().GetAccelerate3DEnabled() && vboxGlobal().is3DAvailable())
+        {
+            display().NotifyScaleFactorChange(m_uScreenId,
+                                              (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER),
+                                              (uint32_t)(dScaleFactor * VBOX_OGL_SCALE_FACTOR_MULTIPLIER));
+        }
 
 #ifdef Q_WS_MAC
Index: /trunk/src/VBox/Main/src-client/DisplayImpl.cpp
===================================================================
--- /trunk/src/VBox/Main/src-client/DisplayImpl.cpp	(revision 54113)
+++ /trunk/src/VBox/Main/src-client/DisplayImpl.cpp	(revision 54114)
@@ -3542,9 +3542,9 @@
     }
     else
-        LogRel(("Attempt to specify OpenGL content scale factor while 3D acceleration is disabled in VM config. Ignored.\n"));
+        AssertMsgFailed(("Attempt to specify OpenGL content scale factor while 3D acceleration is disabled in VM config. Ignored.\n"));
 
     return hr;
 #else
-    LogRel(("Attempt to specify OpenGL content scale factor while corresponding functionality is disabled."));
+    AssertMsgFailed(("Attempt to specify OpenGL content scale factor while corresponding functionality is disabled."));
     return E_UNEXPECTED;
 #endif /* VBOX_WITH_HGCM && VBOX_WITH_CROGL */