From 2b7646399116114a967a5df64266c6879babb10f Mon Sep 17 00:00:00 2001
From: "Mr.Hope" <zhangbowang1998@gmail.com>
Date: Fri, 4 Jun 2021 00:46:47 +0800
Subject: [PATCH] feat(theme-default): improve a11y of CodeGroup (#163)

Co-authored-by: meteorlxy <meteor.lxy@foxmail.com>
---
 .../src/client/components/global/CodeGroup.ts | 71 +++++++++++++++----
 .../components/global/CodeGroupItem.vue       |  6 +-
 .../src/client/styles/code-group.scss         |  4 ++
 3 files changed, 68 insertions(+), 13 deletions(-)

diff --git a/packages/@vuepress/theme-default/src/client/components/global/CodeGroup.ts b/packages/@vuepress/theme-default/src/client/components/global/CodeGroup.ts
index b30c53fc68..f7d229949c 100644
--- a/packages/@vuepress/theme-default/src/client/components/global/CodeGroup.ts
+++ b/packages/@vuepress/theme-default/src/client/components/global/CodeGroup.ts
@@ -8,6 +8,43 @@ export default defineComponent({
     // index of current active item
     const activeIndex = ref(-1)
 
+    // refs of the tab buttons
+    const tabRefs = ref<HTMLButtonElement[]>([])
+
+    // activate next tab
+    const activateNext = (i = activeIndex.value): void => {
+      if (i < tabRefs.value.length - 1) {
+        activeIndex.value = i + 1
+      } else {
+        activeIndex.value = 0
+      }
+      tabRefs.value[activeIndex.value].focus()
+    }
+
+    // activate previous tab
+    const activatePrev = (i = activeIndex.value): void => {
+      if (i > 0) {
+        activeIndex.value = i - 1
+      } else {
+        activeIndex.value = tabRefs.value.length - 1
+      }
+      tabRefs.value[activeIndex.value].focus()
+    }
+
+    // handle keyboard event
+    const keyboardHandler = (event: KeyboardEvent, i: number): void => {
+      if (event.key === ' ' || event.key === 'Enter') {
+        event.preventDefault()
+        activeIndex.value = i
+      } else if (event.key === 'ArrowRight') {
+        event.preventDefault()
+        activateNext(i)
+      } else if (event.key === 'ArrowLeft') {
+        event.preventDefault()
+        activatePrev(i)
+      }
+    }
+
     return () => {
       // NOTICE: here we put the `slots.default()` inside the render function to make
       // the slots reactive, otherwise the slot content won't be changed once the
@@ -23,13 +60,16 @@ export default defineComponent({
           return vnode as VNode & { props: Exclude<VNode['props'], null> }
         })
 
+      // clear tabRefs for HMR
+      tabRefs.value = []
+
       // do not render anything if there is no code-group-item
       if (items.length === 0) {
         return null
       }
 
-      if (activeIndex.value === -1) {
-        // initial state
+      if (activeIndex.value < 0 || activeIndex.value > items.length - 1) {
+        // if `activeIndex` is invalid
 
         // find the index of the code-group-item with `active` props
         activeIndex.value = items.findIndex(
@@ -41,8 +81,6 @@ export default defineComponent({
           activeIndex.value = 0
         }
       } else {
-        // re-render triggered by modifying `activeIndex` ref
-
         // set the active item
         items.forEach((vnode, i) => {
           vnode.props.active = i === activeIndex.value
@@ -56,24 +94,33 @@ export default defineComponent({
           h(
             'ul',
             { class: 'code-group__ul' },
-            items.map((vnode, i) =>
-              h(
+            items.map((vnode, i) => {
+              const isActive = i === activeIndex.value
+
+              return h(
                 'li',
                 { class: 'code-group__li' },
                 h(
                   'button',
                   {
-                    class: `code-group__nav-tab${
-                      i === activeIndex.value
-                        ? ' code-group__nav-tab-active'
-                        : ''
-                    }`,
+                    ref: (element) => {
+                      if (element) {
+                        tabRefs.value[i] = element as HTMLButtonElement
+                      }
+                    },
+                    class: {
+                      'code-group__nav-tab': true,
+                      'code-group__nav-tab-active': isActive,
+                    },
+                    ariaPressed: isActive,
+                    ariaExpanded: isActive,
                     onClick: () => (activeIndex.value = i),
+                    onKeydown: (e) => keyboardHandler(e, i),
                   },
                   vnode.props.title
                 )
               )
-            )
+            })
           )
         ),
         items,
diff --git a/packages/@vuepress/theme-default/src/client/components/global/CodeGroupItem.vue b/packages/@vuepress/theme-default/src/client/components/global/CodeGroupItem.vue
index d5d729409a..f774dbf0b5 100644
--- a/packages/@vuepress/theme-default/src/client/components/global/CodeGroupItem.vue
+++ b/packages/@vuepress/theme-default/src/client/components/global/CodeGroupItem.vue
@@ -1,5 +1,9 @@
 <template>
-  <div class="code-group-item" :class="{ 'code-group-item__active': active }">
+  <div
+    class="code-group-item"
+    :class="{ 'code-group-item__active': active }"
+    :aria-selected="active"
+  >
     <slot />
   </div>
 </template>
diff --git a/packages/@vuepress/theme-default/src/client/styles/code-group.scss b/packages/@vuepress/theme-default/src/client/styles/code-group.scss
index 39da14d5c2..02d0b3d74e 100644
--- a/packages/@vuepress/theme-default/src/client/styles/code-group.scss
+++ b/packages/@vuepress/theme-default/src/client/styles/code-group.scss
@@ -37,6 +37,10 @@
   outline: none;
 }
 
+.code-group__nav-tab:focus-visible {
+  outline: 1px solid rgba(255, 255, 255, 0.9);
+}
+
 .code-group__nav-tab-active {
   border-bottom: var(--c-brand) 1px solid;
 }