plugins/shakecursor: Fix blocking direct scanout

Effects are active by default.

src/plugins/shakecursor/shakecursor.cpp

@@ -47,6 +47,11 @@ bool ShakeCursorEffect::supported()
     return effects->isOpenGLCompositing();
 }
 
+bool ShakeCursorEffect::isActive() const
+{
+    return m_currentMagnification != 1.0;
+}
+
 void ShakeCursorEffect::reconfigure(ReconfigureFlags flags)
 {
     ShakeCursorConfig::self()->read();

src/plugins/shakecursor/shakecursor.h

@@ -29,6 +29,7 @@ public:
 
     static bool supported();
 
+    bool isActive() const override;
     void reconfigure(ReconfigureFlags flags) override;
     void pointerEvent(MouseEvent *event) override;