plugins/shakecursor: Ignore pointer motion events when the pointer is constrained

The main motivation is to prevent the shake cursor from triggering in
video games. It's not a bullet-proof solution though.

src/plugins/shakecursor/shakecursor.cpp

@@ -13,6 +13,7 @@
 #include "opengl/gltexture.h"
 #include "opengl/glutils.h"
 #include "plugins/shakecursor/shakecursorconfig.h"
+#include "pointer_input.h"
 
 namespace KWin
 {
@@ -76,6 +77,10 @@ void ShakeCursorEffect::pointerEvent(MouseEvent *event)
         return;
     }
 
+    if (input()->pointer()->isConstrained()) {
+        return;
+    }
+
     if (const auto shakeFactor = m_shakeDetector.update(event)) {
         update(Transaction{
             .position = m_cursor->pos(),