Restore focus to item that was focused before opening palette

src/App.svelte

@@ -34,15 +34,18 @@
   let items = inputData;
   let itemsFiltered = inputData;
   let fuse = new Fuse(items, optionsFuse);
+  let focusedElement;
 
   onMount(() => {
     initShortCuts(hotkeysGlobal);
     setMainShortCut(hotkey, async () => {
+      focusedElement = document.activeElement
       showModal = true;
       selectedIndex = 0;
       dispatch("opened");
     });
     setAllShortCuts(inputData, async command => {
+      focusedElement = document.activeElement
       showModal = true;
       dispatch("opened");
       await asyncTimeout(200);
@@ -129,18 +132,38 @@
     selectedIndex = 0;
     setItems(inputData);
     showModal = false;
+    if ( ! focusedElement ) {
+      console.error("focusedElement not set")
+    } else {
+      focusedElement.focus()
+    }
   }
 
   function onMobileClick(e) {
     dispatch("opened");
     showModal = true;
     selectedIndex = 0;
   }
+
+  function onMobileFocus(e) {
+    /* Store the item that had focus and assign it to focusedElement.
+       This will allow us to set focus back to it when we exit. */
+
+    // Surprisingly event is defined and has the correct data
+    // even if I don't do this. But I'll explicity pass it via details.
+    // as having event magically defined scares me.
+    let event = e.detail;
+    if (event.relatedTarget && event.relatedTarget.focus) {
+       focusedElement = event.relatedTarget;
+    } else {
+      focusedElement = document.body
+    }
+  }
 </script>
 
 <div id={paletteId}>
   {#if !hideButton}
-    <MobileButton on:click={onMobileClick} />
+    <MobileButton on:click={onMobileClick} on:focus={onMobileFocus}/>
   {/if}
   <PaletteContainer bind:show={showModal}>
     <div slot="search">

src/MobileButton.svelte

@@ -34,7 +34,9 @@
   }
 </style>
 
-<button class="mobile-button" on:click={e => dispatch('click')} title="Click here to open command palette">
+<button class="mobile-button" on:click={e => dispatch('click')}
+    on:focus={e=>dispatch('focus', e)}
+    title="Click here to open command palette.">
   <svg
     xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
     xmlns="http://www.w3.org/2000/svg"