Code

editor.vue

<script setup lang="ts">
import 'prosekit/basic/style.css'

import { createEditor } from 'prosekit/core'
import { ProseKit } from 'prosekit/vue'
import { ref, watchPostEffect } from 'vue'

import { defineExtension } from './extension'
import Toolbar from './toolbar.vue'

const defaultContent =
  '<h1 style="text-align:center;">Heading</h1>' +
  '<p style="text-align:left;">First paragraph</p>' +
  '<p style="text-align:center;">Second paragraph</p>' +
  '<p style="text-align:right;">Third paragraph</p>'

const editor = createEditor({ extension: defineExtension(), defaultContent })

const editorRef = ref<HTMLDivElement | null>(null)
watchPostEffect((onCleanup) => {
  editor.mount(editorRef.value)
  onCleanup(() => editor.unmount())
})
</script>

<template>
  <ProseKit :editor="editor">
    <div class='box-border h-full w-full min-h-36 overflow-y-hidden overflow-x-hidden rounded-md border border-solid border-gray-200 shadow dark:border-zinc-700 flex flex-col bg-white dark:bg-neutral-900'>
      <Toolbar />
      <div class='relative w-full flex-1 box-border overflow-y-scroll'>
        <div
          ref="editorRef"
          spellcheck="false"
          class='ProseMirror box-border min-h-full px-[max(4rem,_calc(50%-20rem))] py-8 outline-none outline-0 [&_span[data-mention="user"]]:text-blue-500 [&_span[data-mention="tag"]]:text-violet-500 [&_pre]:text-white [&_pre]:bg-zinc-800'
        />
      </div>
    </div>
  </ProseKit>
</template>

extension.ts

import { defineBasicExtension } from 'prosekit/basic'
import { union } from 'prosekit/core'
import { defineTextAlign } from 'prosekit/extensions/text-align'

export function defineExtension() {
  return union(
    defineBasicExtension(),
    defineTextAlign({ types: ['paragraph', 'heading'] }),
  )
}

export type EditorExtension = ReturnType<typeof defineExtension>

toolbar.vue

<script setup lang="ts">
import type { Editor, NodeAction } from 'prosekit/core'
import { useEditor } from 'prosekit/vue'

import Button from './button.vue'
import type { EditorExtension } from './extension'

const editor = useEditor<EditorExtension>({ update: true })

function isTextAlignActive(editor: Editor<EditorExtension>, value: string) {
  return Object.values(editor.nodes).some((node: NodeAction<any>) => {
    return node.isActive({ textAlign: value })
  })
}
</script>

<template>
  <div class='z-2 box-border border-zinc-200 dark:border-zinc-800 border-solid border-l-0 border-r-0 border-t-0 border-b flex flex-wrap gap-1 p-2 items-center'>
    <Button
      :pressed="isTextAlignActive(editor, 'left')"
      :disabled="!editor.commands.setTextAlign.canExec('left')"
      @click="() => editor.commands.setTextAlign('left')"
    >
      Left
    </Button>

    <Button
      :pressed="isTextAlignActive(editor, 'center')"
      :disabled="!editor.commands.setTextAlign.canExec('center')"
      @click="() => editor.commands.setTextAlign('center')"
    >
      Center
    </Button>

    <Button
      :pressed="isTextAlignActive(editor, 'right')"
      :disabled="!editor.commands.setTextAlign.canExec('right')"
      @click="() => editor.commands.setTextAlign('right')"
    >
      Right
    </Button>

    <Button
      :pressed="isTextAlignActive(editor, 'justify')"
      :disabled="!editor.commands.setTextAlign.canExec('justify')"
      @click="() => editor.commands.setTextAlign('justify')"
    >
      Justify
    </Button>
  </div>
</template>

button.vue

<script setup lang="ts">
import {
  TooltipContent,
  TooltipRoot,
  TooltipTrigger,
} from 'prosekit/vue/tooltip'

defineProps<{
  pressed?: Boolean
  disabled?: Boolean
  tooltip?: string
}>()

const emit = defineEmits<{
  click: []
}>()
</script>

<template>
  <TooltipRoot>
    <TooltipTrigger class='block'>
      <button
        :data-state="pressed ? 'on' : 'off'"
        :disabled="disabled ? true : undefined"
        class='outline-unset focus-visible:outline-unset flex items-center justify-center rounded-md p-2 font-medium transition focus-visible:ring-2 text-sm focus-visible:ring-zinc-900 dark:focus-visible:ring-zinc-300 disabled:pointer-events-none min-w-9 min-h-9 disabled:opacity-50 hover:disabled:opacity-50 bg-transparent hover:bg-zinc-100 dark:hover:bg-zinc-800 data-[state=on]:bg-gray-200 dark:data-[state=on]:bg-gray-700'
        @click="() => emit('click')"
        @mousedown.prevent
      >
        <slot />
        <span v-if="tooltip" class="sr-only">{{ tooltip }}</span>
      </button>
    </TooltipTrigger>
    <TooltipContent v-if="tooltip" class='z-50 overflow-hidden rounded-md border border-solid bg-zinc-900 dark:bg-zinc-50 px-3 py-1.5 text-xs text-zinc-50 dark:text-zinc-900 shadow-sm [&:not([data-state])]:hidden will-change-transform data-[state=open]:animate-in data-[state=closed]:animate-out data-[state=open]:fade-in-0 data-[state=closed]:fade-out-0 data-[state=open]:zoom-in-95 data-[state=closed]:zoom-out-95 data-[state=open]:animate-duration-150 data-[state=closed]:animate-duration-200 data-[side=bottom]:slide-in-from-top-2 data-[side=bottom]:slide-out-to-top-2 data-[side=left]:slide-in-from-right-2 data-[side=left]:slide-out-to-right-2 data-[side=right]:slide-in-from-left-2 data-[side=right]:slide-out-to-left-2 data-[side=top]:slide-in-from-bottom-2 data-[side=top]:slide-out-to-bottom-2'>
      {{ tooltip }}
    </TooltipContent>
  </TooltipRoot>
</template>