Function visibleLines

samples/common/codehighlight/codemirror.js:3385–3404

(display, doc, viewport)

  // the the current scroll position). viewport may contain top,
  // height, and ensure (see op.scrollToPos) properties.
  function visibleLines(display, doc, viewport) {
    var top = viewport && viewport.top != null ? Math.max(0, viewport.top) : display.scroller.scrollTop;
    top = Math.floor(top - paddingTop(display));
    var bottom = viewport && viewport.bottom != null ? viewport.bottom : top + display.wrapper.clientHeight;

    var from = lineAtHeight(doc, top), to = lineAtHeight(doc, bottom);
    // Ensure is a {from: {line, ch}, to: {line, ch}} object, and
    // forces those lines into the viewport (if possible).
    if (viewport && viewport.ensure) {
      var ensureFrom = viewport.ensure.from.line, ensureTo = viewport.ensure.to.line;
      if (ensureFrom < from) {
        from = ensureFrom;
        to = lineAtHeight(doc, heightAtLine(getLine(doc, ensureFrom)) + display.wrapper.clientHeight);
      } else if (Math.min(ensureTo, doc.lastLine()) >= to) {
        from = lineAtHeight(doc, heightAtLine(getLine(doc, ensureTo)) - display.wrapper.clientHeight);
        to = ensureTo;
      }
    }
    return {from: from, to: Math.max(to, from + 1)}
  }

  // SCROLLING THINGS INTO VIEW