xtermjs/xterm.js

fit addon resizes irratically moving up and down

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#3,584 opened on Dec 22, 2021

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area/addon/fithelp wantedtype/bug

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Description

Upon a resize event, calling fit(), the width does not remain constant when resizing vertically. This results in strange scroll bar positioning, sometimes obstructed, and incomplete fill of the parent control.

Details

  • Browser and browser version: Chrome 1.63.2
  • OS version: Ubuntu 20.04
  • xterm.js version: 4.15.0 / fit 0.5.0

Steps to reproduce

  1. See below for page script
  2. Load the page in Chrome. Make the browser resizable and grab the window edge and shrink or expand the vertical size

Result: the width of the terminal changes, when only the height is supposed to change

The problem appears to be in what xterm resize is doing.

Page script

<!DOCTYPE HTML>
<html>
  <head>
    <title>Example</title>
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
    <link rel="stylesheet" href="node_modules/xterm/css/xterm.css" />
    <script type="text/javascript" src="node_modules/xterm/lib/xterm.js"></script>
    <script type="text/javascript" src="node_modules/xterm-addon-fit/lib/xterm-addon-fit.js"></script>
  </head>

<body>
  <div id="panes" class="panes">
    <div id="terminal-pane" class="terminal-pane"></div>
    <div id="sidebar-pane" class="sidebar-pane"></div>
  </div>

  <script>
    var pane = document.getElementById('terminal-pane');
    var fitAddon = new FitAddon.FitAddon();
    var term = new Terminal();
    term.loadAddon(fitAddon);
    term.open(pane);

    function onSize() {
      fitAddon.fit(); // note: fitAddon.proposeDimensions() only will produce the correct result
    }
    onSize();

    window.addEventListener('resize', onSize, false);
  </script>
  
  <style>
    html, body {
      height: 100%;
      margin: 0;
    }

    div.panes {
      width: 100%;
      height: 100%;
      display: flex;
    }

    div.terminal-pane {
      flex: 70%;
      overflow: visible;
      background-color: red;
    }

    div.sidebar-pane {
      flex: 30%;
    }
  </style>
</body>
</html>

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