输入输入后无意中滚动到顶部的原因是什么[Safari]

要重现问题，我在这里创建了codepen页面：codepen.io

这是聊天的html＆css布局 . 当我向下滚动消息然后我在输入中键入第一个字母 - 可滚动内容滚动到顶部 . 我无法弄清楚问题是什么，所以我要求社区帮助我解释为什么这种交互会影响滚动 .

我希望输入永远不会影响滚动到顶部 .

This problem appears only on apple devices! 在Windows系统上，这非常有效 .

@charset "UTF-8";

/*************************************** SIZES */


/* offsets */


/* cards */


/*************************************** Overrides for Bootstrap variables */


/*!
 * Bootstrap Reboot v4.1.3 (https://getbootstrap.com/)
 * Copyright 2011-2018 The Bootstrap Authors
 * Copyright 2011-2018 Twitter, Inc.
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
 * Forked from Normalize.css, licensed MIT (https://github.com/necolas/normalize.css/blob/master/LICENSE.md)
 */

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  font-family: sans-serif;
  line-height: 1.15;
  -webkit-text-size-adjust: 100%;
  -ms-text-size-adjust: 100%;
  -ms-overflow-style: scrollbar;
  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}

body {
  margin: 0;
  font-family: "Roboto", sans-serif;
  font-size: 1rem;
  font-weight: 400;
  line-height: 1.2;
  color: #000;
  text-align: left;
  background-color: #fff;
}

input,
button,
select,
optgroup,
textarea {
  margin: 0;
  font-family: inherit;
  font-size: inherit;
  line-height: inherit;
}

button,
input {
  overflow: visible;
}

button,
select {
  text-transform: none;
}

[hidden] {
  display: none !important;
}

input:focus,
textarea:focus,
select:focus,
button:focus {
  outline: none;
}

// end: default from Bootstrap (unused css removed for brevity)
// start: user css
.form-control {
  border: none;
  width: 100%;
  background-color: transparent;
}

.chat-input {
  display: flex;
  position: fixed;
  background-color: #fff;
  border-bottom: 1px solid #e4e4e4;
  box-shadow: 0px -4px 15px -3px #dee2e6;
  font-size: 1em;
  padding: 0.6em 1em;
  position: relative;
  border-top: 1px solid #e4e4e4;
  border-bottom: none;
  box-shadow: unset;
}

.chat-input__control {
  flex: 1;
  min-width: unset;
  margin-right: 1em;
}

.chat-message {
  display: flex;
  justify-content: flex-end;
  align-items: flex-end;
  font-size: 1em;
  margin-bottom: 40px;
}

.chat-message__content {
  padding: 0.75em 1.25em;
  background: rgba(0, 123, 255, 0.1);
  position: relative;
  margin-right: 0.5em;
  border-radius: calc(1em * 2);
  text-align: left;
  min-width: 6em;
  line-height: 1.4em;
  word-break: break-word;
}

.chat-message__time {
  position: absolute;
  color: #adb5bd;
  right: 2em;
  bottom: -1.8em;
  font-size: 0.7em;
}

.chat-message_reverse {
  flex-flow: row-reverse;
  align-self: flex-start;
}

.chat-message_system {
  display: block;
  text-align: center;
  -ms-grid-row-align: center;
  align-self: center;
  margin-bottom: 24px;
  margin-top: -8px;
}

.chat-message_system_message {
  color: #adb5bd;
  font-size: 0.9em;
}

.chat-message_reverse .chat-message__content {
  margin-right: 0;
  background: #f8f9fa;
  text-align: left;
}

.chat-message_reverse .chat-message_reverse .chat-message__time {
  left: 2em;
  right: unset;
}

.chat-window {
  display: grid;
  grid-template-rows: auto 1fr 3.4rem;
  font-size: 1em;
  max-height: calc(100vh - 50px);
  background-color: #fff;
}

.chat-window__nav {
  padding-top: 1.25rem;
  padding-bottom: 1.25rem;
  padding-left: 0.6rem;
  padding-right: 0.6rem;
  box-shadow: 0px 4px 15px -3px #dee2e6;
  grid-area: 1/1;
  margin-bottom: 0;
  z-index: 1;
  background-color: #fff;
}

.chat-window__content {
  grid-area: 2/1;
  padding-top: 2.25em;
  padding-left: 0.6rem;
  padding-right: 0.6rem;
  overflow-y: scroll;
  -webkit-overflow-scrolling: touch;
}

.chat-window__input {
  grid-area: 3/1;
}

<div class="chat-window">
  <div class="chat-window__nav">
    Username
  </div>

  <div class="chat-window__content">
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">hello</div>
        <div class="chat-message__time">6:21 PM</div>

      </div>

    </div>
    <div class="chat-message chat-message_system">
      <div class=" chat-message_system_message"> December 6
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">324234</div>
        <div class="chat-message__time">11:31 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_system">
      <div class=" chat-message_system_message"> Today
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">овыроафоаыфа</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">аывфаывафвы</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">фавфафв</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">234325325</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">уцапапарвфвфыв</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">апцупцупуцп</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message">
      <div class="chat-message__content">
        <div class="">gfdhjgjjh</div>
        <div class="chat-message__time">10:30 AM</div>
      </div>
    </div>
    <div class="chat-message">
      <div class="chat-message__content">
        <div class="">sdqdsa</div>
        <div class="chat-message__time">10:41 AM</div>
      </div>
    </div>
    <div class="chat-message">
      <div class="chat-message__content">
        <div class="">safasf</div>
        <div class="chat-message__time">10:41 AM</div>
      </div>
    </div>
    <div class="chat-message">
      <div class="chat-message__content">
        <div class="">36748235235</div>
        <div class="chat-message__time">10:41 AM</div>
      </div>
    </div>
    <div class="chat-message">
      <div class="chat-message__content">
        <div class="">I am exhausted! :(</div>
        <div class="chat-message__time">11:21 AM</div>
      </div>
    </div>
    <div class="chat-message chat-message_reverse">
      <div class="chat-message__content">
        <div class="">I am exhausted too</div>
        <div class="chat-message__time">2:30 PM</div>
      </div>
    </div>

  </div>

  <div class="chat-window__input chat-input">
    <input class="form-control chat-input__control" placeholder="Enter your message" type="text">

  </div>
</div>