学步园

void RenderView::layout()
{
     if (printing())
         m_minPrefWidth = m_maxPrefWidth
= m_width;

     // Use calcWidth/Height to get the newwidth/height,
since this will take the fullpage zoom factor into account.
     bool relayoutChildren = !printing()&&(!m_frameView
|| m_width != viewWidth()||
m_height != viewHeight());
     if (relayoutChildren) {

        setChildNeedsLayout(true, false);
        for (RenderObject* child = firstChild(); child; child = child->nextSibling()) {
            if (child->style()->height().isPercent() || child->style()->minHeight().isPercent() || child->style()->maxHeight().isPercent())
                child->setChildNeedsLayout(true, false);
        }


     }

     // It's safe to check
for control clip here, since controls can never betable cells. If we have a lightweight clip, there can never be any overflow from children.
    if (hasControlClip() && m_overflow)
        clearLayoutOverflow();
}

void RenderBlock::layoutBlock(bool relayoutChildren)
{
    ...
    calcWidth();//先计算宽度
    calcColumnWidth();
   


    m_overflow.clear();   


    if(oldWidth != width()||
oldColumnWidth != desiredColumnWidth())
        relayoutChildren = true;
    clearFloats();

     //另外布局属性为Fixed和absolute的元素
     layoutPositionedObjects(relayoutChildren
|| isRoot());


     // Update our scroll information if we're overflow:auto/scroll/hidden now that we know if we overflow or not.
    updateScrollInfoAfterLayout();


    // Repaint with our new bounds if they are different from our old bounds.
    bool didFullRepaint = repainter.repaintAfterLayout();
    if (!didFullRepaint && repaintTop != repaintBottom && (style()->visibility() == VISIBLE || enclosingLayer()->hasVisibleContent())) {
        // 设置repaintRect


       // Make sure the rect is still non-empty after intersecting for overflow above
        if (!repaintRect.isEmpty()) {
            repaintRectangle(repaintRect); // We need to do a partial repaint of our content.
            if (hasReflection())
                repaintRectangle(reflectedRect(repaintRect));
        }
    }
    setNeedsLayout(false);
}

void RenderBlock::layoutBlockChildren(bool relayoutChildren, int&
maxFloatBottom)
{
int top = borderTop()+ paddingTop();
int bottom = borderBottom()+ paddingBottom()+
horizontalScrollbarHeight();


    // Fieldsets need to find their legend and position it inside the border of the object.
    // The legend then gets skipped during normal layout.
    RenderObject* legend = layoutLegend(relayoutChildren);



//遍历子节点

RenderBox* next = firstChildBox();
    while (next) {
        RenderBox* child = next;
        next = child->nextSiblingBox();

        if (legend == child)
            continue; // Skip the legend, since it has already been positioned up in the fieldset's border.
       // Make sure we layout children if they need it.
        // FIXME: Technically percentage height objects only need a relayout if their percentage isn't going to be turned into
        // an auto value.  Add a method to determine this, so that we can avoid the relayout.
        if (relayoutChildren || ((child->style()->height().isPercent() || child->style()->minHeight().isPercent() || child->style()->maxHeight().isPercent()) && !isRenderView()))
            child->setChildNeedsLayout(true, false);

    // Now do the handling of the bottom of the block, adding in our bottom border/padding and
    // determining the correct collapsed bottom margin information.
    handleBottomOfBlock(top, bottom, marginInfo);
}