diff --git a/ui/src/components/calendar/SVGRect.vue b/ui/src/components/calendar/SVGRect.vue
index 2c410f4..952a7e9 100644
--- a/ui/src/components/calendar/SVGRect.vue
+++ b/ui/src/components/calendar/SVGRect.vue
@@ -1,10 +1,10 @@
 <template>
   <foreignObject
-    :x="Math.round(parent_aspect_ratio * rectangle.left)"
+    :x="Math.round(store.calendar_aspect_ratio * rectangle.left)"
     :y="rectangle.top"
-    :width="Math.round(parent_aspect_ratio * rectangle.width)"
+    :width="Math.round(store.calendar_aspect_ratio * rectangle.width)"
     :height="rectangle.height"
-    :style="`transform: scaleX(${1 / parent_aspect_ratio})`"
+    :style="`transform: scaleX(${1 / store.calendar_aspect_ratio})`"
   >
     <div
       v-if="variant !== undefined"
@@ -16,7 +16,6 @@
     </div>
   </foreignObject>
   <rect
-    ref="rect"
     v-bind="$attrs"
     :class="variant !== undefined ? variant : ''"
     :x="rectangle.left"
@@ -28,6 +27,7 @@
 
 <script lang="ts">
 import { Rectangle } from "@/lib/rectangle";
+import { advent22Store } from "@/plugins/store";
 import { Options, Vue } from "vue-class-component";
 
 type BulmaVariant =
@@ -51,43 +51,7 @@ export default class extends Vue {
   public variant?: BulmaVariant;
   public rectangle!: Rectangle;
 
-  private refreshKey = 0;
-
-  declare $refs: {
-    rect: unknown;
-  };
-
-  private refresh() {
-    window.setTimeout(() => {
-      // don't loop endlessly
-      if (this.refreshKey < 10000) {
-        this.refreshKey++;
-      }
-    }, 100);
-  }
-
-  public get parent_aspect_ratio(): number {
-    this.refreshKey; // read it just to force recompute on change
-
-    if (
-      !(this.$refs.rect instanceof SVGRectElement) ||
-      this.$refs.rect.parentElement === null
-    ) {
-      this.refresh();
-      return 1;
-    }
-
-    const parent = this.$refs.rect.parentElement;
-    const result = parent.clientWidth / parent.clientHeight;
-
-    // force recompute for suspicious results
-    if (result === 0 || result === Infinity) {
-      this.refresh();
-      return 1;
-    }
-
-    return result;
-  }
+  public readonly store = advent22Store();
 }
 </script>
 
diff --git a/ui/src/components/calendar/ThouCanvas.vue b/ui/src/components/calendar/ThouCanvas.vue
index 4a54b74..3774fbf 100644
--- a/ui/src/components/calendar/ThouCanvas.vue
+++ b/ui/src/components/calendar/ThouCanvas.vue
@@ -17,6 +17,7 @@
 
 <script lang="ts">
 import { Vector2D } from "@/lib/vector2d";
+import { advent22Store } from "@/plugins/store";
 import { Options, Vue } from "vue-class-component";
 
 function get_event_thous(event: MouseEvent): Vector2D {
@@ -56,6 +57,17 @@ function mouse_event_validator(event: object, point: object): boolean {
   },
 })
 export default class extends Vue {
+  public readonly store = advent22Store();
+
+  public mounted(): void {
+    new ResizeObserver(([first, ...rest]) => {
+      if (rest.length > 0)
+        console.warn(`Unexpected ${rest.length} extra entries!`);
+
+      this.store.set_calendar_aspect_ratio(first.contentRect);
+    }).observe(this.$el);
+  }
+
   public transform_mouse_event(event: MouseEvent) {
     const point = get_event_thous(event);
     this.$emit(event.type, event, point);
diff --git a/ui/src/plugins/store.ts b/ui/src/plugins/store.ts
index e96d8c6..5a35f09 100644
--- a/ui/src/plugins/store.ts
+++ b/ui/src/plugins/store.ts
@@ -27,6 +27,7 @@ export const advent22Store = defineStore({
       content: "",
       footer: "",
     } as SiteConfigModel,
+    calendar_aspect_ratio: 1,
     user_doors: [] as DoorsSaved,
     next_door_target: null as number | null,
   }),
@@ -98,6 +99,14 @@ export const advent22Store = defineStore({
     toggle_touch_device(): void {
       this.is_touch_device = !this.is_touch_device;
     },
+
+    set_calendar_aspect_ratio(rect: DOMRectReadOnly): void {
+      const result = rect.width / rect.height;
+
+      // filter suspicious results
+      if (result !== 0 && isFinite(result) && !isNaN(result))
+        this.calendar_aspect_ratio = result;
+    },
   },
 });