refactoring

UI/Base/IfNot.svelte

@@ -0,0 +1,18 @@
+<script lang="ts">
+  import { UIEventSource } from "../../Logic/UIEventSource";
+  import { onDestroy } from "svelte";
+
+  /**
+   * For some stupid reason, it is very hard to let {#if} work together with UIEventSources, so we wrap then here
+   */
+  export let condition: UIEventSource<boolean>;
+  let _c = !condition.data;
+  onDestroy(condition.addCallback(c => {
+    _c = !c;
+    return false
+  }))
+</script>
+
+{#if _c}
+  <slot></slot>
+{/if}