Function updateDisplayInner

GUI/codemirror/lib/codemirror.js:583–644

(cm, visible, forced)

  // (returning false) when there is nothing to be done and forced is
  // false.
  function updateDisplayInner(cm, visible, forced) {
    var display = cm.display, doc = cm.doc;
    if (!display.wrapper.offsetWidth) {
      resetView(cm);
      return;
    }

    // Bail out if the visible area is already rendered and nothing changed.
    if (!forced && visible.from >= display.viewFrom && visible.to <= display.viewTo &&
        countDirtyView(cm) == 0)
      return;

    if (maybeUpdateLineNumberWidth(cm))
      resetView(cm);
    var dims = getDimensions(cm);

    // Compute a suitable new viewport (from & to)
    var end = doc.first + doc.size;
    var from = Math.max(visible.from - cm.options.viewportMargin, doc.first);
    var to = Math.min(end, visible.to + cm.options.viewportMargin);
    if (display.viewFrom < from && from - display.viewFrom < 20) from = Math.max(doc.first, display.viewFrom);
    if (display.viewTo > to && display.viewTo - to < 20) to = Math.min(end, display.viewTo);
    if (sawCollapsedSpans) {
      from = visualLineNo(cm.doc, from);
      to = visualLineEndNo(cm.doc, to);
    }

    var different = from != display.viewFrom || to != display.viewTo ||
      display.lastSizeC != display.wrapper.clientHeight;
    adjustView(cm, from, to);

    display.viewOffset = heightAtLine(getLine(cm.doc, display.viewFrom));
    // Position the mover div to align with the current scroll position
    cm.display.mover.style.top = display.viewOffset + "px";

    var toUpdate = countDirtyView(cm);
    if (!different && toUpdate == 0 && !forced) return;

    // For big changes, we hide the enclosing element during the
    // update, since that speeds up the operations on most browsers.
    var focused = activeElt();
    if (toUpdate > 4) display.lineDiv.style.display = "none";
    patchDisplay(cm, display.updateLineNumbers, dims);
    if (toUpdate > 4) display.lineDiv.style.display = "";
    // There might have been a widget with a focused element that got
    // hidden or updated, if so re-focus it.
    if (focused && activeElt() != focused && focused.offsetHeight) focused.focus();

    // Prevent selection and cursors from interfering with the scroll
    // width.
    removeChildren(display.cursorDiv);
    removeChildren(display.selectionDiv);

    if (different) {
      display.lastSizeC = display.wrapper.clientHeight;
      startWorker(cm, 400);
    }