diff --git a/src/components/ruler.vue b/src/components/ruler.vue
index a51b0eb..f85c446 100644
--- a/src/components/ruler.vue
+++ b/src/components/ruler.vue
@@ -108,7 +108,10 @@ const scale = ref(1)
 const offsetX = ref(0)
 const offsetY = ref(0)
 
-
+const containerRef = ref(null)
+const rulerSize = 40
+const containerWidth = ref(0)
+const containerHeight = ref(0)
 
 const contentWidth = computed(() => containerWidth.value - rulerSize)
 const contentHeight = computed(() => containerHeight.value - rulerSize)