Can it flexbox? Chat window with input at the bottom, chats scrolling up

Question

Seems like it should be possible with flexbox, but I can't figure it out.

http://codepen.io/MichaelJCole/pen/NGBVGe

Goals:

textarea (for typeing in messages) stays at the bottom the whole time.
chats start at the bottom, then scroll up as needed.
If you use the "Google Hangouts", like the message app in that.

Here's the markup:

 <div id="chatBar">
    <div id="chatList">
      <div class="chat mine">hello world</div>
      <div class="chat theirs">hello moon</div>
    </div>
    <input id="chatBarInput" class="form-control" type="textarea">
  </div>

And here's the CSS:

html, body { height: 100%; }
#chatBar {
  height: 100%;
  display: flex;
  flex-flow: column nowrap;
  justify-content: flex-end;
  overflow: none;
}

#chatList {
  flex: 0 1 auto;
  display: flex;
  flex-flow: column nowrap;
  justify-content: flex-end;
  overflow-y: scroll;
}

#chatBarInput {
  flex: 1 0 auto;
}

.chat {
  flex: none;
  align-self: flex-start;
  background-color: lightgreen;
}

.chat.mine {
  align-self: flex-end;
  background-color: pink;
}

I can't get #chatBar to "squeeze" #chatList without setting a height. Which is what I was trying to avoid by using flexbox :-/

Sorry, I'm a backend coder. Tried a bunch of stuff, then pared it down for the CodePen.

Seems like I should be able to tell the inner flexbox to scroll, while leaving the outer alone. Do I have to use position:absolute?

I'm not entirely sure what you're trying to accomplish. But I see you're using `height: 100%` in your flex container (`#chatBar`). *100% of what?* You need to provide a frame of reference when using percentage heights in CSS. Add this to your code: `html, body { height: 100%; }` — Michael Benjamin, Nov 04 '15 at 04:59
Ok, good point. I added that to the codepen, but still the same trouble. When the body is small, the input scrolls off the bottom. I want the outer flexbox to place the input *at* the bottom, and never scroll. The inner flexbox should place items at the bottom, and scroll if they overflow. Does that help? — Michael Cole, Nov 04 '15 at 05:03

score 16 · Accepted Answer · answered Nov 04 '15 at 05:53

I can't get #chatBar to "squeeze" #chatList without setting a height. Which is what I was trying to avoid by using flexbox

You had the flex-basis set to auto for all elements. Without explicit height, the flex model will automatically try to accommodate everything inside the available space by shrinking or expanding the elements. This is why you are unable to get the #chatList to work as intended. The div itself as well as the individual chats all expand or shrink within the available space.

What you should do is to start simple:

#chatBar {
    height: 100%; overflow: hidden;
    display: flex; flex-flow: column;
}
#chatList {
    /* grow or shrink as required from flex-basis height of 20% */
    flex: 1 1 20%; 
    display: flex; flex-direction: column; 
    overflow: auto;
} 

/* do not grow or shrink with a flex-basis height of 80% */
#chatBarInput { flex: 0 0 80%; }

And you will be able to see it working. You could then take it further from here.

Your modified codepen: http://codepen.io/Abhitalks/pen/ZbjNvQ/

Goals:

textarea (for typeing in messages) stays at the bottom the whole time.

chats start at the bottom, then scroll up as needed.

If you use the "Google Hangouts", like the message app in that.

The trick would be to use flex-direction: column-reverse and prepend the new messages to the container instead of appending those.

I took an old answer of mine and changed the layout to flex-model for a demo of this purpose. You can peruse the code to see how it's done.

Demo Fiddle: http://jsfiddle.net/abhitalks/khj4903t/

Demo Snippet:

var btn  = document.getElementById('btn'), 
    inp  = document.getElementById('inp'), 
    chats = document.getElementById('chatWindow')
;
btn.addEventListener('click', postMsg);

inp.addEventListener('keyup', function(e) {
 if (e.keyCode == 13) { postMsg(); }
});

function postMsg() {
 var msg  = inp.value,
        bubble  = document.createElement('div'),
        p   = document.createElement('p');
    if (msg.trim().length <= 0) { return; }
    bubble.classList.add('bubble');
    bubble.classList.add('right');
    p.textContent = msg;
    bubble.appendChild(p);
    inp.value = '';
    chats.insertBefore(bubble, chats.firstChild);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html, body { height: 100%; overflow: hidden; }
.wrap { 
    margin: 8px; height: 90%; width: 50%; 
    display: flex; flex-direction: column;
}
.container {
    flex: 1 1 90%; display: flex; flex-direction: column; 
    background-color: #eee; border: 1px solid #ccc; overflow: auto;
}
.form { flex: 0 0 32px; display: flex; border: 1px solid #ddd; }
.form > input[type=text] { flex: 1 1 auto; border: 1px solid #eee; }
.form > input[type=button] { flex: 0 0 20%; border: 1px solid #eee; }
.bubble { flex: 1 1 auto; clear: both; } /* clear the floats here on parent */
.bubble p {
    border-radius: 5px;
    padding: 8px; margin: 8px 12px;
    max-width: 80%;  /* this will make it not exceed 80% and then wrap */
    position: relative; transition: background-color 0.5s; 
}
.left p { background-color: #ccc; float: left; } /* floated left */
.right p { background-color: #33c; color: #fff; float: right; } /* floated right */
/* classes below are only for arrows, not relevant */
.left p::before {
    content: ''; position: absolute;
    width: 0; height: 0; left: -8px; top: 8px;
    border-top: 4px solid transparent;
    border-right: 8px solid #ccc;
    border-bottom: 4px solid transparent;
}
.right p::after {
    content: ''; position: absolute;
    width: 0; height: 0; right: -8px; bottom: 8px;
    border-top: 4px solid transparent;
    border-left: 8px solid #33c;
    border-bottom: 4px solid transparent;
}

<div class="wrap">
    <div id="chatWindow" class="container">
        <div class="bubble left"><p>msg</p></div>
        <div class="bubble left"><p>long message</p></div>
        <div class="bubble right"><p>ultra long message which can wrap at eighty percent </p></div>
        <div class="bubble left"><p>lorem ipsum</p></div>
        <div class="bubble right"><p>very long message</p></div>    
        <div class="bubble right"><p>one more message</p></div>    
        <div class="bubble left"><p>lorem ipsum</p></div>
        <div class="bubble right"><p>another message</p></div>    
        <div class="bubble left"><p>lorem ipsum</p></div>
        <div class="bubble right"><p>yet another message</p></div>    
        <div class="bubble left"><p>lorem ipsum</p></div>
    </div>
    <div id="inputWindow" class="form">
        <input id="inp" type="text" />
        <input id="btn" type="button" value="Send" />
    </div>
</div>

Amazingly helpful!!! I was blowing hours trying to accomplish this, and your example saved the day. — skiindude22, Oct 09 '21 at 22:43

score 2 · Answer 2 · answered Nov 04 '15 at 05:55

The vertical scrollbar on the browser exists because you've set a height: 100% to the body, and the user agent stylesheet applies a default margin to the body, typically 8px all around. So, 100% + 16px launches the vertical scroll.

Add this to your CSS: body { margin: 0; }

To apply the scrollbar to the inner flexbox (.chatlist), here are two adjustments:

#chatList {
  flex: 0 1 75px; /* specify a height */
  display: flex;
  flex-flow: column nowrap;
  /* justify-content: flex-end; REMOVE */ 
  overflow-y: scroll;
}

DEMO: http://jsfiddle.net/5p2vy31p/1/

Can it flexbox? Chat window with input at the bottom, chats scrolling up

2 Answers2

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