feat: make `MkImgWithBlurhash` transitionable (#10500)

* feat: make `MkImgWithBlurhash` animatable

* refactor: split out transition styles

* fix: bug

* test: waitFor image loads

* style: remove unused await

* fix

* fix type error

---------

Co-authored-by: tamaina <tamaina@hotmail.co.jp>

3 files changed, 88 insertions, 24 deletions

diff --git a/packages/frontend/src/components/MkGalleryPostPreview.stories.impl.ts b/packages/frontend/src/components/MkGalleryPostPreview.stories.impl.ts
index e46a708192..57b3e75513 100644
--- a/packages/frontend/src/components/MkGalleryPostPreview.stories.impl.ts
+++ b/packages/frontend/src/components/MkGalleryPostPreview.stories.impl.ts
@@ -28,9 +28,11 @@ export const Default = {
 	async play({ canvasElement }) {
 		const canvas = within(canvasElement);
 		const links = canvas.getAllByRole('link');
-		await expect(links).toHaveLength(2);
-		await expect(links[0]).toHaveAttribute('href', `/gallery/${galleryPost().id}`);
-		await expect(links[1]).toHaveAttribute('href', `/@${galleryPost().user.username}@${galleryPost().user.host}`);
+		expect(links).toHaveLength(2);
+		expect(links[0]).toHaveAttribute('href', `/gallery/${galleryPost().id}`);
+		expect(links[1]).toHaveAttribute('href', `/@${galleryPost().user.username}@${galleryPost().user.host}`);
+		const images = canvas.getAllByRole<HTMLImageElement>('img');
+		await waitFor(() => expect(Promise.all(images.map((image) => image.decode()))).resolves.toBeDefined());
 	},
 	args: {
 		post: galleryPost(),
diff --git a/packages/frontend/src/components/MkGalleryPostPreview.vue b/packages/frontend/src/components/MkGalleryPostPreview.vue
index 944f5ad97b..4f8f7b945a 100644
--- a/packages/frontend/src/components/MkGalleryPostPreview.vue
+++ b/packages/frontend/src/components/MkGalleryPostPreview.vue
@@ -1,9 +1,21 @@
 <template>
 <MkA :to="`/gallery/${post.id}`" class="ttasepnz _panel" tabindex="-1" @pointerenter="enterHover" @pointerleave="leaveHover">
 	<div class="thumbnail">
-		<ImgWithBlurhash class="img" :hash="post.files[0].blurhash"/>
 		<Transition>
-			<ImgWithBlurhash v-if="show" class="img layered" :src="post.files[0].thumbnailUrl" :hash="post.files[0].blurhash"/>
+			<ImgWithBlurhash
+				class="img layered"
+				:transition="safe ? null : {
+					enterActiveClass: $style.transition_toggle_enterActive,
+					leaveActiveClass: $style.transition_toggle_leaveActive,
+					enterFromClass: $style.transition_toggle_enterFrom,
+					leaveToClass: $style.transition_toggle_leaveTo,
+					enterToClass: $style.transition_toggle_enterTo,
+					leaveFromClass: $style.transition_toggle_leaveFrom,
+				}"
+				:src="post.files[0].thumbnailUrl"
+				:hash="post.files[0].blurhash"
+				:force-blurhash="!show"
+			/>
 		</Transition>
 	</div>
 	<article>
@@ -28,7 +40,8 @@ const props = defineProps<{
 }>();
 
 const hover = ref(false);
-const show = computed(() => defaultStore.state.nsfw === 'ignore' || defaultStore.state.nsfw === 'respect' && !props.post.isSensitive || hover.value);
+const safe = computed(() => defaultStore.state.nsfw === 'ignore' || defaultStore.state.nsfw === 'respect' && !props.post.isSensitive);
+const show = computed(() => safe.value || hover.value);
 
 function enterHover(): void {
 	hover.value = true;
@@ -39,6 +52,27 @@ function leaveHover(): void {
 }
 </script>
 
+<style lang="scss" module>
+.transition_toggle_enterActive,
+.transition_toggle_leaveActive {
+	transition: opacity 0.5s;
+	position: absolute;
+	top: 0;
+	left: 0;
+}
+
+.transition_toggle_enterFrom,
+.transition_toggle_leaveTo {
+	opacity: 0;
+}
+
+.transition_toggle_enterTo,
+.transition_toggle_leaveFrom {
+	transition: none;
+	opacity: 1;
+}
+</style>
+
 <style lang="scss" scoped>
 .ttasepnz {
 	display: block;
@@ -66,7 +100,7 @@ function leaveHover(): void {
 		width: 100%;
 		height: 100%;
 		position: absolute;
-		transition: all 0.5s ease;
+		transition: transform 0.5s ease;
 
 		> .img {
 			width: 100%;
@@ -76,16 +110,6 @@ function leaveHover(): void {
 			&.layered {
 				position: absolute;
 				top: 0;
-
-				&.v-enter-active,
-				&.v-leave-active {
-					transition: opacity 0.5s ease;
-				}
-
-				&.v-enter-from,
-				&.v-leave-to {
-					opacity: 0;
-				}
 			}
 		}
 	}
diff --git a/packages/frontend/src/components/MkImgWithBlurhash.vue b/packages/frontend/src/components/MkImgWithBlurhash.vue
index 048dcc7045..2bdb059614 100644
--- a/packages/frontend/src/components/MkImgWithBlurhash.vue
+++ b/packages/frontend/src/components/MkImgWithBlurhash.vue
@@ -1,15 +1,37 @@
 <template>
 <div :class="[$style.root, { [$style.cover]: cover }]" :title="title ?? ''">
-	<canvas v-if="!loaded || forceBlurhash" ref="canvas" :class="$style.canvas" :width="width" :height="height" :title="title ?? ''"/>
-	<img v-if="src && !forceBlurhash" v-show="loaded" :class="$style.img" :src="src" :title="title ?? ''" :alt="alt ?? ''" @load="onLoad"/>
+	<img v-if="!loaded && src && !forceBlurhash" :class="$style.loader" :src="src" @load="onLoad"/>
+	<Transition
+		mode="in-out"
+		:enter-active-class="defaultStore.state.animation && (props.transition?.enterActiveClass ?? $style['transition_toggle_enterActive']) || undefined"
+		:leave-active-class="defaultStore.state.animation && (props.transition?.leaveActiveClass ?? $style['transition_toggle_leaveActive']) || undefined"
+		:enter-from-class="defaultStore.state.animation && props.transition?.enterFromClass || undefined"
+		:leave-to-class="defaultStore.state.animation && props.transition?.leaveToClass || undefined"
+		:enter-to-class="defaultStore.state.animation && props.transition?.enterToClass || undefined"
+		:leave-from-class="defaultStore.state.animation && props.transition?.leaveFromClass || undefined"
+	>
+		<canvas v-if="!loaded || forceBlurhash" ref="canvas" :class="$style.canvas" :width="width" :height="height" :title="title"/>
+		<img v-else :class="$style.img" :src="src ?? undefined" :title="title ?? undefined" :alt="alt ?? undefined"/>
+	</Transition>
 </div>
 </template>
 
 <script lang="ts" setup>
-import { onMounted, watch } from 'vue';
+import { onMounted, shallowRef, useCssModule, watch } from 'vue';
 import { decode } from 'blurhash';
+import { defaultStore } from '@/store';
+
+const $style = useCssModule();
 
 const props = withDefaults(defineProps<{
+	transition?: {
+		enterActiveClass?: string;
+		leaveActiveClass?: string;
+		enterFromClass?: string;
+		leaveToClass?: string;
+		enterToClass?: string;
+		leaveFromClass?: string;
+	} | null;
 	src?: string | null;
 	hash?: string;
 	alt?: string | null;
@@ -19,6 +41,7 @@ const props = withDefaults(defineProps<{
 	cover?: boolean;
 	forceBlurhash?: boolean;
 }>(), {
+	transition: null,
 	src: null,
 	alt: '',
 	title: null,
@@ -28,7 +51,7 @@ const props = withDefaults(defineProps<{
 	forceBlurhash: false,
 });
 
-const canvas = $shallowRef<HTMLCanvasElement>();
+const canvas = shallowRef<HTMLCanvasElement>();
 let loaded = $ref(false);
 let width = $ref(props.width);
 let height = $ref(props.height);
@@ -51,15 +74,15 @@ watch([() => props.width, () => props.height], () => {
 });
 
 function draw() {
-	if (props.hash == null) return;
+	if (props.hash == null || !canvas.value) return;
 	const pixels = decode(props.hash, width, height);
-	const ctx = canvas.getContext('2d');
+	const ctx = canvas.value.getContext('2d');
 	const imageData = ctx!.createImageData(width, height);
 	imageData.data.set(pixels);
 	ctx!.putImageData(imageData, 0, 0);
 }
 
-watch(() => props.hash, () => {
+watch([() => props.hash, canvas], () => {
 	draw();
 });
 
@@ -69,6 +92,21 @@ onMounted(() => {
 </script>
 
 <style lang="scss" module>
+.transition_toggle_enterActive,
+.transition_toggle_leaveActive {
+	position: absolute;
+	top: 0;
+	left: 0;
+}
+
+.loader {
+	position: absolute;
+	top: 0;
+	left: 0;
+	width: 0;
+	height: 0;
+}
+
 .root {
 	position: relative;
 	width: 100%;