demo/indentwrap.html

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<title>CodeMirror: Indented wrapped line demo</title>
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    <li><a class=active href="#">Indented wrapped line</a>
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<article>
<h2>Indented wrapped line demo</h2>
<form><textarea id="code" name="code">
<!doctype html>
<body>
  <h2 id="overview">Overview</h2>

  <p>CodeMirror is a code-editor component that can be embedded in Web pages. The core library provides <em>only</em> the editor component, no accompanying buttons, auto-completion, or other IDE functionality. It does provide a rich API on top of which such functionality can be straightforwardly implemented. See the <a href="#addons">add-ons</a> included in the distribution, and the <a href="https://github.com/jagthedrummer/codemirror-ui">CodeMirror UI</a> project, for reusable implementations of extra features.</p>

  <p>CodeMirror works with language-specific modes. Modes are JavaScript programs that help color (and optionally indent) text written in a given language. The distribution comes with a number of modes (see the <a href="../mode/"><code>mode/</code></a> directory), and it isn't hard to <a href="#modeapi">write new ones</a> for other languages.</p>
</body>
</textarea></form>

    <p>This page uses a hack on top of the <code>"renderLine"</code>
    event to make wrapped text line up with the base indentation of
    the line.</p>

    <script>
      var editor = CodeMirror.fromTextArea(document.getElementById("code"), {
        lineNumbers: true,
        lineWrapping: true,
        mode: "text/html"
      });
      var charWidth = editor.defaultCharWidth(), basePadding = 4;
      editor.on("renderLine", function(cm, line, elt) {
        var off = CodeMirror.countColumn(line.text, null, cm.getOption("tabSize")) * charWidth;
        elt.style.textIndent = "-" + off + "px";
        elt.style.paddingLeft = (basePadding + off) + "px";
      });
      editor.refresh();
    </script>

  </article>