feat(3d-nds): lag detection

app/components/LagModal.vue

@@ -0,0 +1,28 @@
+<script setup lang="ts">
+const emit = defineEmits<{ close: [] }>();
+
+const app = useAppStore();
+
+const keep3d = () => {
+  app.lagDetected = false;
+  emit("close");
+};
+
+const switch2d = () => {
+  app.setRenderingMode("2d");
+  emit("close");
+};
+</script>
+
+<template>
+  <UModal :open="true" :dismissible="false" :title="$t('lagModal.title')" :ui="{ footer: 'justify-end' }">
+    <template #body>
+      {{ $t('lagModal.body') }}
+    </template>
+
+    <template #footer>
+      <UButton variant="ghost" color="neutral" :label="$t('lagModal.keep3d')" @click="keep3d" />
+      <UButton color="neutral" :label="$t('lagModal.switch2d')" @click="switch2d" />
+    </template>
+  </UModal>
+</template>

app/components/NDS3D.vue

@@ -195,7 +195,12 @@ watch(
   { immediate: true },
 );
 
-const { onRender } = useLoop();
+const { onRender, onBeforeRender } = useLoop();
+
+const LAG_FPS_THRESHOLD = 440;
+const LAG_DURATION_SECS = 1;
+let lagSeconds = 0;
+let lagCheckDone = false;
 
 const HINT_SPRITE_SCALE = 2;
 const HINT_SPRITE_DPR = 4;
@@ -337,10 +342,30 @@ useKeyUp(({ ndsButton }) => {
   }
 });
 
-onRender(({ delta }) => {
+// lag detection
+onBeforeRender(({ delta }) => {
+  if (!lagCheckDone) {
+    const fps = 1 / delta;
+    if (fps < LAG_FPS_THRESHOLD) {
+      lagSeconds += delta;
+      if (lagSeconds >= LAG_DURATION_SECS) {
+        lagCheckDone = true;
+        app.lagDetected = true;
+      }
+    } else {
+      lagSeconds = 0;
+    }
+  }
+});
+
+// upate screens
+onRender(() => {
   if (topScreenTexture) topScreenTexture.needsUpdate = true;
   if (bottomScreenTexture) bottomScreenTexture.needsUpdate = true;
+});
 
+// update physical buttons
+onBeforeRender(({ delta }) => {
   // cross
   const crossButton = meshes.get(CROSS_BUTTON);
   if (crossButton) {