matrix-chat/src/components/newMessage.vue

<template>
  <div class="newMessageBanner">
    <label for="newMessageInput"></label>
    <textarea @input="resizeMessageBanner()" ref="newMessageInput" id="newMessageInput" class="newMessageInput"
              autocomplete="off" placeholder="type a message ..." v-model="msg.content.text" />
    <icon @click.native="sendMessage()" id="sendMessageBtn" style="position: absolute; right: 1rem; bottom: 0.5rem;"
          ic="./sym/ic_send_white_24px.svg" />
  </div>
</template>

<script>
import icon from '@/components/icon.vue';
import main from '@/main.js';

export default {
  name: "newMessage",
  components: {
    icon
  },
  methods: {
    sendMessage(){
      if (this.msg.content.text !== "") {
        this.msg.time = Date.now()
        main.methods.sendWebSocket(this.msg)
        this.msg.content.text = ""
        document.getElementById("messagesContainer").style.height = "calc(100% - 7rem)"
        document.getElementById("newMessageInput").style.height = "1.25rem"
        //let msgContainer = document.getElementById("messagesContainer")
        //msgContainer.scrollTo(0, msgContainer.scrollHeight)
      }
    },
    resizeMessageBanner(){
      let id = this.$refs.newMessageInput
      id.style.height = '1.25rem'
      id.style.height = `${id.scrollHeight}px`
      let msgContainer = document.getElementById("messagesContainer")
      msgContainer.style.height
          = `calc(100% - ${id.parentElement.clientHeight}px - 3rem)`
    }
  },
  data(){
    return {
      msg: {
        type: "message",
        time: Date.now(),
        content: {
          user: "you",
          text: ""
        }
      },
      chatroom: main.data().chatroom
    }
  }
}
</script>

<style scoped>
  .newMessageBanner{
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: min-content;
    min-height: 4rem;
    background-color: #1d1d1d;
    border-radius: 1rem 1rem 0 0;
  }
  .newMessageInput{
    position: relative;
    margin-top: 1.5rem;
    margin-bottom: 1rem;
    left: 2rem;
    min-height: 1.25rem;
    max-height: 10rem;
    width: calc(100% - 7rem);
    height: 1.25rem;
    background-color: #fff0;
    border: 0 solid #fff0;
    color: #fff;
    font-size: 1rem;
    resize: none;
    vertical-align: middle;
    font-family: Avenir, Helvetica, Arial, sans-serif;
  }

</style>