feat: option to follow the system-wide light/dark mode (#71)

src/components/LightDarkSwitch.svelte

@@ -0,0 +1,89 @@
+<script lang="ts">
+
+import Icon from "@iconify/svelte"
+import {i18n} from '@i18n/translation'
+import I18nKey from '@i18n/i18nKey'
+import {LIGHT_MODE, DARK_MODE, AUTO_MODE, setTheme, getStoredTheme} from '../utils/setting-utils.ts'
+import {onMount} from "svelte";
+
+const seq = [LIGHT_MODE, DARK_MODE, AUTO_MODE]
+let mode = AUTO_MODE
+
+onMount(() => {
+    mode = getStoredTheme()
+})
+
+function switchScheme(newMode: string) {
+    mode = newMode
+    setTheme(newMode)
+}
+
+function toggleScheme() {
+    let i = 0
+    for (; i < seq.length; i++) {
+        if (seq[i] === mode) {
+            break
+        }
+    }
+    switchScheme(seq[(i + 1) % seq.length])
+}
+
+function showPanel() {
+    const panel = document.querySelector('#light-dark-panel')
+    panel.classList.remove('float-panel-closed')
+}
+
+function hidePanel() {
+    const panel = document.querySelector('#light-dark-panel')
+    panel.classList.add('float-panel-closed')
+}
+
+</script>
+
+<!-- z-50 make the panel higher than other float panels -->
+<div class="relative z-50" role="menu" tabindex="-1" on:mouseleave={hidePanel}>
+    <button aria-label="Light/Dark Mode" role="menuitem" class="relative btn-plain h-11 w-11 rounded-lg active:scale-90" id="scheme-switch" on:click={toggleScheme} on:mouseenter={showPanel}>
+        <div class="absolute" class:opacity-0={mode !== LIGHT_MODE}>
+            <Icon icon="material-symbols:wb-sunny-outline-rounded" class="text-[1.25rem]"></Icon>
+        </div>
+        <div class="absolute" class:opacity-0={mode !== DARK_MODE}>
+            <Icon icon="material-symbols:dark-mode-outline-rounded" class="text-[1.25rem]"></Icon>
+        </div>
+        <div class="absolute" class:opacity-0={mode !== AUTO_MODE}>
+            <Icon icon="material-symbols:radio-button-partial-outline" class="text-[1.25rem]"></Icon>
+        </div>
+    </button>
+
+    <div id="light-dark-panel" class="hidden lg:block absolute transition float-panel-closed top-11 -right-2 pt-5" >
+        <div class="card-base float-panel p-2">
+            <button class="flex transition whitespace-nowrap items-center justify-start w-full btn-plain h-9 rounded-lg px-3 font-medium active:scale-95 mb-0.5"
+                    class:current-setting={mode === LIGHT_MODE}
+                    on:click={() => switchScheme(LIGHT_MODE)}
+            >
+                <Icon icon="material-symbols:wb-sunny-outline-rounded" class="text-[1.25rem] mr-3"></Icon>
+                {i18n(I18nKey.lightMode)}
+            </button>
+            <button class="flex transition whitespace-nowrap items-center justify-start w-full btn-plain h-9 rounded-lg px-3 font-medium active:scale-95 mb-0.5"
+                    class:current-setting={mode === DARK_MODE}
+                    on:click={() => switchScheme(DARK_MODE)}
+            >
+                <Icon icon="material-symbols:dark-mode-outline-rounded" class="text-[1.25rem] mr-3"></Icon>
+                {i18n(I18nKey.darkMode)}
+            </button>
+            <button class="flex transition whitespace-nowrap items-center justify-start w-full btn-plain h-9 rounded-lg px-3 font-medium active:scale-95"
+                    class:current-setting={mode === AUTO_MODE}
+                    on:click={() => switchScheme(AUTO_MODE)}
+            >
+                <Icon icon="material-symbols:radio-button-partial-outline" class="text-[1.25rem] mr-3"></Icon>
+                {i18n(I18nKey.systemMode)}
+            </button>
+        </div>
+    </div>
+</div>
+
+<style lang="css">
+.current-setting {
+    background: var(--btn-plain-bg-hover);
+    color: var(--primary);
+}
+</style>