feat: improve vue node video preview loading and a11y (#7558)

## Summary

Applies appropriate logic from below PRs (which affected image
outputs/previews) to video previews

- https://github.com/Comfy-Org/ComfyUI_frontend/pull/7268: don't port
the 250ms logic for videos, as it is not as relevant - videos typically
take longer than 250ms and most browsers have a built-in loading state
that will be displayed between component mount and video onloaded that
we don't want to flash. Use the native video loaded event instead
- https://github.com/Comfy-Org/ComfyUI_frontend/pull/7252: apply to
videos 1-for-1

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7558-feat-improve-vue-node-video-preview-loading-and-a11y-2cb6d73d365081eab4dcfeb1e62c553b)
by [Unito](https://www.unito.io)

src/renderer/extensions/vueNodes/VideoPreview.vue

@@ -2,16 +2,20 @@
   <div
     v-if="imageUrls.length > 0"
     class="video-preview group relative flex size-full min-h-16 min-w-16 flex-col px-2"
-    tabindex="0"
-    role="region"
-    :aria-label="$t('g.videoPreview')"
-    @mouseenter="handleMouseEnter"
-    @mouseleave="handleMouseLeave"
     @keydown="handleKeyDown"
   >
     <!-- Video Wrapper -->
     <div
+      ref="videoWrapperEl"
       class="relative h-full w-full grow overflow-hidden rounded-[5px] bg-node-component-surface"
+      tabindex="0"
+      role="region"
+      :aria-label="$t('g.videoPreview')"
+      :aria-busy="showLoader"
+      @mouseenter="handleMouseEnter"
+      @mouseleave="handleMouseLeave"
+      @focusin="handleFocusIn"
+      @focusout="handleFocusOut"
     >
       <!-- Error State -->
       <div
@@ -27,18 +31,18 @@
 
       <!-- Loading State -->
       <Skeleton
-        v-if="isLoading && !videoError"
+        v-if="showLoader && !videoError"
         class="absolute inset-0 size-full"
         border-radius="5px"
-        width="16rem"
-        height="16rem"
+        width="100%"
+        height="100%"
       />
 
       <!-- Main Video -->
       <video
         v-if="!videoError"
         :src="currentVideoUrl"
-        :class="cn('block size-full object-contain', isLoading && 'invisible')"
+        :class="cn('block size-full object-contain', showLoader && 'invisible')"
         controls
         loop
         playsinline
@@ -47,10 +51,13 @@
       />
 
       <!-- Floating Action Buttons (appear on hover) -->
-      <div v-if="isHovered" class="actions absolute top-2 right-2 flex gap-1">
+      <div
+        v-if="isHovered || isFocused"
+        class="actions absolute top-2 right-2 flex gap-2.5"
+      >
         <!-- Download Button -->
         <button
-          class="action-btn cursor-pointer rounded-lg border-0 bg-white p-2 text-black shadow-sm transition-all duration-200 hover:bg-smoke-100"
+          :class="actionButtonClass"
           :title="$t('g.downloadVideo')"
           :aria-label="$t('g.downloadVideo')"
           @click="handleDownload"
@@ -60,7 +67,7 @@
 
         <!-- Close Button -->
         <button
-          class="action-btn cursor-pointer rounded-lg border-0 bg-white p-2 text-black shadow-sm transition-all duration-200 hover:bg-smoke-100"
+          :class="actionButtonClass"
           :title="$t('g.removeVideo')"
           :aria-label="$t('g.removeVideo')"
           @click="handleRemove"
@@ -94,7 +101,7 @@
       <span v-if="videoError" class="text-red-400">
         {{ $t('g.errorLoadingVideo') }}
       </span>
-      <span v-else-if="isLoading" class="text-smoke-400">
+      <span v-else-if="showLoader" class="text-smoke-400">
         {{ $t('g.loading') }}...
       </span>
       <span v-else>
@@ -126,12 +133,18 @@ const props = defineProps<VideoPreviewProps>()
 const { t } = useI18n()
 const nodeOutputStore = useNodeOutputStore()
 
+const actionButtonClass =
+  'flex h-8 min-h-8 items-center justify-center gap-2.5 rounded-lg border-0 bg-button-surface px-2 py-2 text-button-surface-contrast shadow-sm transition-colors duration-200 hover:bg-button-hover-surface focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-button-surface-contrast focus-visible:ring-offset-2 focus-visible:ring-offset-transparent cursor-pointer'
+
 // Component state
 const currentIndex = ref(0)
 const isHovered = ref(false)
+const isFocused = ref(false)
 const actualDimensions = ref<string | null>(null)
 const videoError = ref(false)
-const isLoading = ref(false)
+const showLoader = ref(false)
+
+const videoWrapperEl = ref<HTMLDivElement>()
 
 // Computed values
 const currentVideoUrl = computed(() => props.imageUrls[currentIndex.value])
@@ -149,16 +162,16 @@ watch(
     // Reset loading and error states when URLs change
     actualDimensions.value = null
     videoError.value = false
-    isLoading.value = newUrls.length > 0
+    showLoader.value = newUrls.length > 0
   },
-  { deep: true }
+  { deep: true, immediate: true }
 )
 
 // Event handlers
 const handleVideoLoad = (event: Event) => {
   if (!event.target || !(event.target instanceof HTMLVideoElement)) return
   const video = event.target
-  isLoading.value = false
+  showLoader.value = false
   videoError.value = false
   if (video.videoWidth && video.videoHeight) {
     actualDimensions.value = `${video.videoWidth} x ${video.videoHeight}`
@@ -166,7 +179,7 @@ const handleVideoLoad = (event: Event) => {
 }
 
 const handleVideoError = () => {
-  isLoading.value = false
+  showLoader.value = false
   videoError.value = true
   actualDimensions.value = null
 }
@@ -194,7 +207,7 @@ const setCurrentIndex = (index: number) => {
   if (index >= 0 && index < props.imageUrls.length) {
     currentIndex.value = index
     actualDimensions.value = null
-    isLoading.value = true
+    showLoader.value = true
     videoError.value = false
   }
 }
@@ -207,6 +220,16 @@ const handleMouseLeave = () => {
   isHovered.value = false
 }
 
+const handleFocusIn = () => {
+  isFocused.value = true
+}
+
+const handleFocusOut = (event: FocusEvent) => {
+  if (!videoWrapperEl.value?.contains(event.relatedTarget as Node)) {
+    isFocused.value = false
+  }
+}
+
 const getNavigationDotClass = (index: number) => {
   return [
     'w-2 h-2 rounded-full transition-all duration-200 border-0 cursor-pointer',