fix: display IME characters during composition

[ras0q]

resolve #2262

Fixed it so that during IME input, values are updated only within the Editor, and once the IME confirms the input, the value is passed to the caller.

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commit: 9399c19

[antfu]

I am afraid this is too complex and would be hard to understand and maintain. Don't we have a better way to do that? Or at least I think it would be better to move them into a headless component

[ras0q]

I didn't know InputEvent had an isComposing property.
https://developer.mozilla.org/en-US/docs/Web/API/InputEvent/isComposing

Furthermore, since the target property of InputEvent contains the character being input via IME, we could handle most processing in onInput.
(However, since onInput doesn't fire when IME input ends, we need to use onCompositionEnd...)

How does this look? Should we further separate this into a headless component?

const localContent = ref(content.value)
watch(content, (v) => {
  if (v !== localContent.value) {
    localContent.value = v
  }
})

function onInput(e: Event) {
  if (!(e instanceof InputEvent) || !(e.target instanceof HTMLTextAreaElement)) {
    return
  }

  if (e.isComposing) {
    localContent.value = e.target.value
  }
  else {
    content.value = e.target.value
  }
}

function onCompositionEnd() {
  content.value = localContent.value
}