gecko-dev/layout/base/nsLayoutUtils.cpp

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#include "nsLayoutUtils.h"
#include "nsIFrame.h"
#include "nsIPresContext.h"
#include "nsIContent.h"
#include "nsFrameList.h"
#include "nsLayoutAtoms.h"
#include "nsIAtom.h"
#include "nsCSSPseudoElements.h"
#include "nsIView.h"

/**
 * A namespace class for static layout utilities.
 */

/**
 * GetFirstChildFrame returns the first "real" child frame of a
 * given frame.  It will descend down into pseudo-frames (unless the
 * pseudo-frame is the :before generated frame).   
 * @param aPresContext the prescontext
 * @param aFrame the frame
 * @param aFrame the frame's content node
 */
static nsIFrame*
GetFirstChildFrame(nsIPresContext* aPresContext,
                   nsIFrame*       aFrame,
                   nsIContent*     aContent)
{
  NS_PRECONDITION(aFrame, "NULL frame pointer");

  nsIFrame* childFrame;

  // Get the first child frame
  aFrame->FirstChild(aPresContext, nsnull, &childFrame);

  // If the child frame is a pseudo-frame, then return its first child.
  // Note that the frame we create for the generated content is also a
  // pseudo-frame and so don't drill down in that case
  if (childFrame &&
      childFrame->IsPseudoFrame(aContent) &&
      !childFrame->IsGeneratedContentFrame()) {
    return GetFirstChildFrame(aPresContext, childFrame, aContent);
  }

  return childFrame;
}

/**
 * GetLastChildFrame returns the last "real" child frame of a
 * given frame.  It will descend down into pseudo-frames (unless the
 * pseudo-frame is the :after generated frame).   
 * @param aPresContext the prescontext
 * @param aFrame the frame
 * @param aFrame the frame's content node
 */
static nsIFrame*
GetLastChildFrame(nsIPresContext* aPresContext,
                  nsIFrame*       aFrame,
                  nsIContent*     aContent)
{
  NS_PRECONDITION(aFrame, "NULL frame pointer");

  // Get the last in flow frame
  nsIFrame* lastInFlow = aFrame->GetLastInFlow();

  // Get the last child frame
  nsIFrame* firstChildFrame;
  lastInFlow->FirstChild(aPresContext, nsnull, &firstChildFrame);
  if (firstChildFrame) {
    nsFrameList frameList(firstChildFrame);
    nsIFrame*   lastChildFrame = frameList.LastChild();

    NS_ASSERTION(lastChildFrame, "unexpected error");

    // Get the frame's first-in-flow. This matters in case the frame has
    // been continuted across multiple lines
    lastChildFrame = lastChildFrame->GetFirstInFlow();
    
    // If the last child frame is a pseudo-frame, then return its last child.
    // Note that the frame we create for the generated content is also a
    // pseudo-frame and so don't drill down in that case
    if (lastChildFrame &&
        lastChildFrame->IsPseudoFrame(aContent) &&
        !lastChildFrame->IsGeneratedContentFrame()) {
      return GetLastChildFrame(aPresContext, lastChildFrame, aContent);
    }

    return lastChildFrame;
  }

  return nsnull;
}

// static
nsIFrame*
nsLayoutUtils::GetBeforeFrame(nsIFrame* aFrame, nsIPresContext* aPresContext)
{
  NS_PRECONDITION(aFrame, "NULL frame pointer");
#ifdef DEBUG
  nsIFrame* prevInFlow = nsnull;
  aFrame->GetPrevInFlow(&prevInFlow);
  NS_ASSERTION(!prevInFlow, "aFrame must be first-in-flow");
#endif
  
  nsIFrame* firstFrame = GetFirstChildFrame(aPresContext, aFrame, aFrame->GetContent());

  if (firstFrame && IsGeneratedContentFor(nsnull, firstFrame,
                                          nsCSSPseudoElements::before)) {
    return firstFrame;
  }

  return nsnull;
}

// static
nsIFrame*
nsLayoutUtils::GetAfterFrame(nsIFrame* aFrame, nsIPresContext* aPresContext)
{
  NS_PRECONDITION(aFrame, "NULL frame pointer");

  nsIFrame* lastFrame = GetLastChildFrame(aPresContext, aFrame, aFrame->GetContent());

  if (lastFrame && IsGeneratedContentFor(nsnull, lastFrame,
                                         nsCSSPseudoElements::after)) {
    return lastFrame;
  }

  return nsnull;
}

// static
nsIFrame*
nsLayoutUtils::GetPageFrame(nsIFrame* aFrame)
{
  for (nsIFrame* frame = aFrame; frame; frame = frame->GetParent()) {
    nsCOMPtr<nsIAtom> type;
    frame->GetFrameType(getter_AddRefs(type));
    if (type.get() == nsLayoutAtoms::pageFrame) {
      return frame;
    }
  }
  return nsnull;
}

// static
PRBool
nsLayoutUtils::IsGeneratedContentFor(nsIContent* aContent,
                                     nsIFrame* aFrame,
                                     nsIAtom* aPseudoElement)
{
  NS_PRECONDITION(aFrame, "Must have a frame");
  NS_PRECONDITION(aPseudoElement, "Must have a pseudo name");

  if (!aFrame->IsGeneratedContentFrame()) {
    return PR_FALSE;
  }

  if (aContent && aFrame->GetContent() != aContent) {
    return PR_FALSE;
  }

  return aFrame->GetStyleContext()->GetPseudoType() == aPseudoElement;
}

// static
PRBool
nsLayoutUtils::IsProperAncestorFrame(nsIFrame* aAncestorFrame, nsIFrame* aFrame,
                                     nsIFrame* aCommonAncestor)
{
  if (aFrame == aCommonAncestor) {
    return PR_FALSE;
  }
  
  nsIFrame* parentFrame = aFrame->GetParent();

  while (parentFrame != aCommonAncestor) {
    if (parentFrame == aAncestorFrame) {
      return PR_TRUE;
    }

    parentFrame = parentFrame->GetParent();
  }

  return PR_FALSE;
}

// static
PRInt32
nsLayoutUtils::CompareTreePosition(nsIContent* aContent1, nsIContent* aContent2,
                                   nsIContent* aCommonAncestor) {
  NS_PRECONDITION(aContent1, "aContent1 must not be null");
  NS_PRECONDITION(aContent2, "aContent2 must not be null");

  nsAutoVoidArray content1Ancestors;
  nsIContent* c1;
  for (c1 = aContent1; c1 && c1 != aCommonAncestor; c1 = c1->GetParent()) {
    content1Ancestors.AppendElement(c1);
  }
  if (!c1 && aCommonAncestor) {
    // So, it turns out aCommonAncestor was not an ancestor of c1. Oops.
    // Never mind. We can continue as if aCommonAncestor was null.
    aCommonAncestor = nsnull;
  }

  nsAutoVoidArray content2Ancestors;
  nsIContent* c2;
  for (c2 = aContent2; c2 && c2 != aCommonAncestor; c2 = c2->GetParent()) {
    content2Ancestors.AppendElement(c2);
  }
  if (!c2 && aCommonAncestor) {
    // So, it turns out aCommonAncestor was not an ancestor of c2.
    // We need to retry with no common ancestor hint.
    return CompareTreePosition(aContent1, aContent2, nsnull);
  }
  
  int last1 = content1Ancestors.Count() - 1;
  int last2 = content2Ancestors.Count() - 1;
  nsIContent* content1Ancestor = nsnull;
  nsIContent* content2Ancestor = nsnull;
  while (last1 >= 0 && last2 >= 0
         && ((content1Ancestor = NS_STATIC_CAST(nsIContent*, content1Ancestors.ElementAt(last1)))
             == (content2Ancestor = NS_STATIC_CAST(nsIContent*, content2Ancestors.ElementAt(last2))))) {
    last1--;
    last2--;
  }

  if (last1 < 0) {
    if (last2 < 0) {
      NS_ASSERTION(aContent1 == aContent2, "internal error?");
      return 0;
    } else {
      // aContent1 is an ancestor of aContent2
      return -1;
    }
  } else {
    if (last2 < 0) {
      // aContent2 is an ancestor of aContent1
      return 1;
    } else {
      // content1Ancestor != content2Ancestor, so they must be siblings with the same parent
      nsIContent* parent = content1Ancestor->GetParent();
      NS_ASSERTION(parent, "no common ancestor at all???");
      if (!parent) { // different documents??
        return 0;
      }

      PRInt32 index1 = parent->IndexOf(content1Ancestor);
      PRInt32 index2 = parent->IndexOf(content2Ancestor);
      if (index1 < 0 || index2 < 0) {
        // one of them must be anonymous; we can't determine the order
        return 0;
      }

      return index1 - index2;
    }
  }
}

// static
nsIFrame* nsLayoutUtils::GetLastSibling(nsIFrame* aFrame) {
  if (!aFrame) {
    return nsnull;
  }

  nsIFrame* next;
  while ((next = aFrame->GetNextSibling()) != nsnull) {
    aFrame = next;
  }
  return aFrame;
}

// static
nsIView*
nsLayoutUtils::FindSiblingViewFor(nsIView* aParentView, nsIFrame* aFrame) {
  nsIFrame* parentViewFrame = NS_STATIC_CAST(nsIFrame*, aParentView->GetClientData());
  nsIContent* parentViewContent = parentViewFrame ? parentViewFrame->GetContent() : nsnull;
  for (nsIView* insertBefore = aParentView->GetFirstChild(); insertBefore;
       insertBefore = insertBefore->GetNextSibling()) {
    nsIFrame* f = NS_STATIC_CAST(nsIFrame*, insertBefore->GetClientData());
    if (!f) {
      // this view could be some anonymous view attached to a meaningful parent
      for (nsIView* searchView = insertBefore->GetParent(); searchView;
           searchView = searchView->GetParent()) {
        f = NS_STATIC_CAST(nsIFrame*, searchView->GetClientData());
        if (f) {
          break;
        }
      }
      NS_ASSERTION(f, "Can't find a frame anywhere!");
    }
    if (f && CompareTreePosition(aFrame->GetContent(),
                                 f->GetContent(), parentViewContent) > 0) {
      // aFrame's content is after f's content, so put our view before f's view
      return insertBefore;
    }
  }
  return nsnull;
}