path: root/layout/xul/nsSprocketLayout.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

//
// Eric Vaughan
// Netscape Communications
//
// See documentation in associated header file
//

#include "nsBoxLayoutState.h"
#include "nsSprocketLayout.h"
#include "nsPresContext.h"
#include "nsCOMPtr.h"
#include "nsIContent.h"
#include "nsContainerFrame.h"
#include "nsBoxFrame.h"
#include "StackArena.h"
#include "mozilla/Likely.h"
#include "mozilla/CSSOrderAwareFrameIterator.h"
#include <algorithm>

using mozilla::StyleDirection;
using namespace mozilla;

nsBoxLayout* nsSprocketLayout::gInstance = nullptr;

static Maybe<CSSOrderAwareFrameIterator> IterFor(nsIFrame* aBoxFrame) {
  Maybe<CSSOrderAwareFrameIterator> ret;
  if (aBoxFrame->IsXULBoxFrame()) {
    ret.emplace(aBoxFrame, FrameChildListID::Principal,
                CSSOrderAwareFrameIterator::ChildFilter::IncludeAll,
                CSSOrderAwareFrameIterator::OrderState::Unknown,
                CSSOrderAwareFrameIterator::OrderingProperty::BoxOrdinalGroup);
  }
  return ret;
}

nsresult NS_NewSprocketLayout(nsCOMPtr<nsBoxLayout>& aNewLayout) {
  if (!nsSprocketLayout::gInstance) {
    nsSprocketLayout::gInstance = new nsSprocketLayout();
    NS_IF_ADDREF(nsSprocketLayout::gInstance);
  }
  // we have not instance variables so just return our static one.
  aNewLayout = nsSprocketLayout::gInstance;
  return NS_OK;
}

/*static*/
void nsSprocketLayout::Shutdown() { NS_IF_RELEASE(gInstance); }

nsSprocketLayout::nsSprocketLayout() = default;

bool nsSprocketLayout::IsXULHorizontal(nsIFrame* aBox) {
  return aBox->HasAnyStateBits(NS_STATE_IS_HORIZONTAL);
}

void nsSprocketLayout::GetFrameState(nsIFrame* aBox, nsFrameState& aState) {
  aState = aBox->GetStateBits();
}

static StyleDirection GetFrameDirection(nsIFrame* aBox) {
  return aBox->StyleVisibility()->mDirection;
}

static void HandleBoxPack(nsIFrame* aBox, const nsFrameState& aFrameState,
                          nscoord& aX, nscoord& aY, const nsRect& aOriginalRect,
                          const nsRect& aClientRect) {
  // In the normal direction we lay out our kids in the positive direction
  // (e.g., |x| will get bigger for a horizontal box, and |y| will get bigger
  // for a vertical box).  In the reverse direction, the opposite is true. We'll
  // be laying out each child at a smaller |x| or |y|.
  StyleDirection frameDirection = GetFrameDirection(aBox);

  if (aFrameState & NS_STATE_IS_HORIZONTAL) {
    if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL) {
      // The normal direction. |x| increases as we move through our children.
      aX = aClientRect.x;
    } else {
      // The reverse direction. |x| decreases as we move through our children.
      aX = aClientRect.x + aOriginalRect.width;
    }
    // |y| is always in the normal direction in horizontal boxes
    aY = aClientRect.y;
  } else {
    // take direction property into account for |x| in vertical boxes
    if (frameDirection == StyleDirection::Ltr) {
      // The normal direction. |x| increases as we move through our children.
      aX = aClientRect.x;
    } else {
      // The reverse direction. |x| decreases as we move through our children.
      aX = aClientRect.x + aOriginalRect.width;
    }
    if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL) {
      // The normal direction. |y| increases as we move through our children.
      aY = aClientRect.y;
    } else {
      // The reverse direction. |y| decreases as we move through our children.
      aY = aClientRect.y + aOriginalRect.height;
    }
  }

  // Get our pack/alignment information.
  nsIFrame::Halignment halign = aBox->GetXULHAlign();
  nsIFrame::Valignment valign = aBox->GetXULVAlign();

  // The following code handles box PACKING.  Packing comes into play in the
  // case where the computed size for all of our children (now stored in our
  // client rect) is smaller than the size available for the box (stored in
  // |aOriginalRect|).
  //
  // Here we adjust our |x| and |y| variables accordingly so that we start at
  // the beginning, middle, or end of the box.
  //
  // XXXdwh JUSTIFY needs to be implemented!
  if (aFrameState & NS_STATE_IS_HORIZONTAL) {
    switch (halign) {
      case nsBoxFrame::hAlign_Left:
        break;  // Nothing to do.  The default initialized us properly.

      case nsBoxFrame::hAlign_Center:
        if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL)
          aX += (aOriginalRect.width - aClientRect.width) / 2;
        else
          aX -= (aOriginalRect.width - aClientRect.width) / 2;
        break;

      case nsBoxFrame::hAlign_Right:
        if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL)
          aX += (aOriginalRect.width - aClientRect.width);
        else
          aX -= (aOriginalRect.width - aClientRect.width);
        break;  // Nothing to do for the reverse dir.  The default initialized
                // us properly.
    }
  } else {
    switch (valign) {
      case nsBoxFrame::vAlign_Top:
      case nsBoxFrame::vAlign_BaseLine:  // This value is technically impossible
                                         // to specify for pack.
        break;  // Don't do anything.  We were initialized correctly.

      case nsBoxFrame::vAlign_Middle:
        if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL)
          aY += (aOriginalRect.height - aClientRect.height) / 2;
        else
          aY -= (aOriginalRect.height - aClientRect.height) / 2;
        break;

      case nsBoxFrame::vAlign_Bottom:
        if (aFrameState & NS_STATE_IS_DIRECTION_NORMAL)
          aY += (aOriginalRect.height - aClientRect.height);
        else
          aY -= (aOriginalRect.height - aClientRect.height);
        break;
    }
  }
}

NS_IMETHODIMP
nsSprocketLayout::XULLayout(nsIFrame* aBox, nsBoxLayoutState& aState) {
  // See if we are collapsed. If we are, then simply iterate over all our
  // children and give them a rect of 0 width and height.
  if (aBox->IsXULCollapsed()) {
    for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
      nsBoxFrame::LayoutChildAt(aState, iter->get(), nsRect(0, 0, 0, 0));
    }
    return NS_OK;
  }

  nsBoxLayoutState::AutoReflowDepth depth(aState);
  mozilla::AutoStackArena arena;

  // ----- figure out our size ----------
  const nsSize originalSize = aBox->GetSize();

  // -- make sure we remove our border and padding  ----
  nsRect clientRect;
  aBox->GetXULClientRect(clientRect);

  // |originalClientRect| represents the rect of the entire box (excluding
  // borders and padding).  We store it here because we're going to use
  // |clientRect| to hold the required size for all our kids.  As an example,
  // consider an hbox with a specified width of 300.  If the kids total only 150
  // pixels of width, then we have 150 pixels left over.  |clientRect| is going
  // to hold a width of 150 and is going to be adjusted based off the value of
  // the PACK property.  If flexible objects are in the box, then the two rects
  // will match.
  nsRect originalClientRect(clientRect);

  // The frame state contains cached knowledge about our box, such as our
  // orientation and direction.
  nsFrameState frameState = nsFrameState(0);
  GetFrameState(aBox, frameState);

  // Build a list of our children's desired sizes and computed sizes
  nsBoxSize* boxSizes = nullptr;
  nsComputedBoxSize* computedBoxSizes = nullptr;

  nscoord min = 0;
  nscoord max = 0;
  int32_t flexes = 0;
  PopulateBoxSizes(aBox, aState, boxSizes, min, max, flexes);

  // The |size| variable will hold the total size of children along the axis of
  // the box.  Continuing with the example begun in the comment above, size
  // would be 150 pixels.
  nscoord size = clientRect.width;
  if (!IsXULHorizontal(aBox)) size = clientRect.height;
  ComputeChildSizes(aBox, aState, size, boxSizes, computedBoxSizes);

  // After the call to ComputeChildSizes, the |size| variable contains the
  // total required size of all the children.  We adjust our clientRect in the
  // appropriate dimension to match this size.  In our example, we now assign
  // 150 pixels into the clientRect.width.
  //
  // The variables |min| and |max| hold the minimum required size box must be
  // in the OPPOSITE orientation, e.g., for a horizontal box, |min| is the
  // minimum height we require to enclose our children, and |max| is the maximum
  // height required to enclose our children.
  if (IsXULHorizontal(aBox)) {
    clientRect.width = size;
    if (clientRect.height < min) clientRect.height = min;

    if (frameState & NS_STATE_AUTO_STRETCH) {
      if (clientRect.height > max) clientRect.height = max;
    }
  } else {
    clientRect.height = size;
    if (clientRect.width < min) clientRect.width = min;

    if (frameState & NS_STATE_AUTO_STRETCH) {
      if (clientRect.width > max) clientRect.width = max;
    }
  }

  // With the sizes computed, now it's time to lay out our children.
  bool finished;
  nscoord passes = 0;

  // We flow children at their preferred locations (along with the appropriate
  // computed flex). After we flow a child, it is possible that the child will
  // change its size.  If/when this happens, we have to do another pass.
  // Typically only 2 passes are required, but the code is prepared to do as
  // many passes as are necessary to achieve equilibrium.
  nscoord x = 0;
  nscoord y = 0;
  nscoord origX = 0;
  nscoord origY = 0;

  // |childResized| lets us know if a child changed its size after we attempted
  // to lay it out at the specified size.  If this happens, we usually have to
  // do another pass.
  bool childResized = false;

  // |passes| stores our number of passes.  If for any reason we end up doing
  // more than, say, 10 passes, we assert to indicate that something is
  // seriously screwed up.
  passes = 0;
  do {
    // Always assume that we're done.  This will change if, for example,
    // children don't stay the same size after being flowed.
    finished = true;

    // Handle box packing.
    HandleBoxPack(aBox, frameState, x, y, originalClientRect, clientRect);

    // Now that packing is taken care of we set up a few additional
    // tracking variables.
    origX = x;
    origY = y;

    // Now we iterate over our box children and our box size lists in
    // parallel.  For each child, we look at its sizes and figure out
    // where to place it.
    nsComputedBoxSize* childComputedBoxSize = computedBoxSizes;
    nsBoxSize* childBoxSize = boxSizes;

    auto iter = IterFor(aBox);
    int32_t count = 0;
    while ((iter && !iter->AtEnd()) || (childBoxSize && childBoxSize->bogus)) {
      // If for some reason, our lists are not the same length, we guard
      // by bailing out of the loop.
      if (childBoxSize == nullptr) {
        MOZ_ASSERT_UNREACHABLE("Lists not the same length.");
        break;
      }

      nscoord width = clientRect.width;
      nscoord height = clientRect.height;

      if (!childBoxSize->bogus) {
        nsIFrame* child = iter->get();

        // We have a valid box size entry.  This entry already contains
        // information about our sizes along the axis of the box (e.g., widths
        // in a horizontal box).  If our default ALIGN is not stretch, however,
        // then we also need to know the child's size along the opposite axis.
        if (!(frameState & NS_STATE_AUTO_STRETCH)) {
          nsSize prefSize = child->GetXULPrefSize(aState);
          nsSize minSize = child->GetXULMinSize(aState);
          nsSize maxSize = child->GetXULMaxSize(aState);
          prefSize = nsIFrame::XULBoundsCheck(minSize, prefSize, maxSize);

          AddXULMargin(child, prefSize);
          width = std::min(prefSize.width, originalClientRect.width);
          height = std::min(prefSize.height, originalClientRect.height);
        }
      }

      // Obtain the computed size along the axis of the box for this child from
      // the computedBoxSize entry. We store the result in |width| for
      // horizontal boxes and |height| for vertical boxes.
      if (frameState & NS_STATE_IS_HORIZONTAL)
        width = childComputedBoxSize->size;
      else
        height = childComputedBoxSize->size;

      // Adjust our x/y for the left/right spacing.
      if (frameState & NS_STATE_IS_HORIZONTAL) {
        if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
          x += (childBoxSize->left);
        else
          x -= (childBoxSize->right);
      } else {
        if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
          y += (childBoxSize->left);
        else
          y -= (childBoxSize->right);
      }

      // Now we build a child rect.
      nscoord rectX = x;
      nscoord rectY = y;
      if (!(frameState & NS_STATE_IS_DIRECTION_NORMAL)) {
        if (frameState & NS_STATE_IS_HORIZONTAL)
          rectX -= width;
        else
          rectY -= height;
      }

      // We now create an accurate child rect based off our computed size
      // information.
      nsRect childRect(rectX, rectY, width, height);

      // Sanity check against our clientRect.  It is possible that a child
      // specified a size that is too large to fit.  If that happens, then we
      // have to grow our client rect.  Remember, clientRect is not the total
      // rect of the enclosing box.  It currently holds our perception of how
      // big the children needed to be.
      if (childRect.width > clientRect.width)
        clientRect.width = childRect.width;

      if (childRect.height > clientRect.height)
        clientRect.height = childRect.height;

      // Either |nextX| or |nextY| is updated by this function call, according
      // to our axis.
      nscoord nextX = x;
      nscoord nextY = y;

      ComputeChildsNextPosition(aBox, x, y, nextX, nextY, childRect);

      // Now we further update our nextX/Y along our axis.
      // We also set childRect.y/x along the opposite axis appropriately for a
      // stretch alignment.  (Non-stretch alignment is handled below.)
      if (frameState & NS_STATE_IS_HORIZONTAL) {
        if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
          nextX += (childBoxSize->right);
        else
          nextX -= (childBoxSize->left);
        childRect.y = originalClientRect.y;
      } else {
        if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
          nextY += (childBoxSize->right);
        else
          nextY -= (childBoxSize->left);
        if (GetFrameDirection(aBox) == StyleDirection::Ltr) {
          childRect.x = originalClientRect.x;
        } else {
          // keep the right edge of the box the same
          childRect.x =
              clientRect.x + originalClientRect.width - childRect.width;
        }
      }

      // If we encounter a completely bogus box size, we just leave this child
      // completely alone and continue through the loop to the next child.
      if (childBoxSize->bogus) {
        childComputedBoxSize = childComputedBoxSize->next;
        childBoxSize = childBoxSize->next;
        count++;
        x = nextX;
        y = nextY;
        // FIXME(emilio): shouldn't this update `child` / `iter`? This looks
        // broken.
        continue;
      }

      nsIFrame* child = iter->get();
      nsMargin margin(0, 0, 0, 0);

      bool layout = true;

      // Deflate the rect of our child by its margin.
      child->GetXULMargin(margin);
      childRect.Deflate(margin);
      if (childRect.width < 0) childRect.width = 0;
      if (childRect.height < 0) childRect.height = 0;

      // Now we're trying to figure out if we have to lay out this child, i.e.,
      // to call the child's XULLayout method.
      if (passes > 0) {
        layout = false;
      } else {
        // Always perform layout if we are dirty or have dirty children
        if (!child->IsSubtreeDirty()) {
          layout = false;
        }
      }

      nsRect oldRect(child->GetRect());

      // Non-stretch alignment will be handled in AlignChildren(), so don't
      // change child out-of-axis positions yet.
      if (!(frameState & NS_STATE_AUTO_STRETCH)) {
        if (frameState & NS_STATE_IS_HORIZONTAL) {
          childRect.y = oldRect.y;
        } else {
          childRect.x = oldRect.x;
        }
      }

      // We computed a childRect.  Now we want to set the bounds of the child to
      // be that rect. If our old rect is different, then we know our size
      // changed and we cache that fact in the |sizeChanged| variable.

      child->SetXULBounds(aState, childRect);
      bool sizeChanged = (childRect.width != oldRect.width ||
                          childRect.height != oldRect.height);

      if (sizeChanged) {
        // Our size is different.  Sanity check against our maximum allowed size
        // to ensure we didn't exceed it.
        nsSize minSize = child->GetXULMinSize(aState);
        nsSize maxSize = child->GetXULMaxSize(aState);
        maxSize = nsIFrame::XULBoundsCheckMinMax(minSize, maxSize);

        // make sure the size is in our max size.
        if (childRect.width > maxSize.width) childRect.width = maxSize.width;

        if (childRect.height > maxSize.height)
          childRect.height = maxSize.height;

        // set it again
        child->SetXULBounds(aState, childRect);
      }

      // If we already determined that layout was required or if our size has
      // changed, then we make sure to call layout on the child, since its
      // children may need to be shifted around as a result of the size change.
      if (layout || sizeChanged) child->XULLayout(aState);

      // If the child was a block or inline (e.g., HTML) it may have changed its
      // rect *during* layout. We have to check for this.
      nsRect newChildRect(child->GetRect());

      if (!newChildRect.IsEqualInterior(childRect)) {
#ifdef DEBUG_GROW
        printf(" GREW from (%d,%d) -> (%d,%d)\n", childRect.width,
               childRect.height, newChildRect.width, newChildRect.height);
#endif
        newChildRect.Inflate(margin);
        childRect.Inflate(margin);

        // The child changed size during layout.  The ChildResized method
        // handles this scenario.
        ChildResized(aBox, aState, child, childBoxSize, childComputedBoxSize,
                     boxSizes, computedBoxSizes, childRect, newChildRect,
                     clientRect, flexes, finished);

        // We note that a child changed size, which means that another pass will
        // be required.
        childResized = true;

        // Now that a child resized, it's entirely possible that OUR rect is too
        // small.  Now we ensure that |originalClientRect| is grown to
        // accommodate the size of |clientRect|.
        if (clientRect.width > originalClientRect.width)
          originalClientRect.width = clientRect.width;

        if (clientRect.height > originalClientRect.height)
          originalClientRect.height = clientRect.height;

        if (!(frameState & NS_STATE_IS_DIRECTION_NORMAL)) {
          // Our childRect had its XMost() or YMost() (depending on our layout
          // direction), positioned at a certain point.  Ensure that the
          // newChildRect satisfies the same constraint.  Note that this is
          // just equivalent to adjusting the x/y by the difference in
          // width/height between childRect and newChildRect.  So we don't need
          // to reaccount for the left and right of the box layout state again.
          if (frameState & NS_STATE_IS_HORIZONTAL)
            newChildRect.x = childRect.XMost() - newChildRect.width;
          else
            newChildRect.y = childRect.YMost() - newChildRect.height;
        }

        if (!(frameState & NS_STATE_IS_HORIZONTAL)) {
          if (GetFrameDirection(aBox) != StyleDirection::Ltr) {
            // keep the right edge the same
            newChildRect.x = childRect.XMost() - newChildRect.width;
          }
        }

        // If the child resized then recompute its position.
        ComputeChildsNextPosition(aBox, x, y, nextX, nextY, newChildRect);

        if (newChildRect.width >= margin.left + margin.right &&
            newChildRect.height >= margin.top + margin.bottom)
          newChildRect.Deflate(margin);

        if (childRect.width >= margin.left + margin.right &&
            childRect.height >= margin.top + margin.bottom)
          childRect.Deflate(margin);

        child->SetXULBounds(aState, newChildRect);

        // If we are the first box that changed size, then we don't need to do a
        // second pass
        if (count == 0) finished = true;
      }

      // Now update our x/y finally.
      x = nextX;
      y = nextY;

      // Move to the next child.
      childComputedBoxSize = childComputedBoxSize->next;
      childBoxSize = childBoxSize->next;

      iter->Next();
      count++;
    }

    // Sanity-checking code to ensure we don't do an infinite # of passes.
    passes++;
    NS_ASSERTION(passes < 10, "A Box's child is constantly growing!!!!!");
    if (passes >= 10) break;
  } while (false == finished);

  // Get rid of our size lists.
  while (boxSizes) {
    nsBoxSize* toDelete = boxSizes;
    boxSizes = boxSizes->next;
    delete toDelete;
  }

  while (computedBoxSizes) {
    nsComputedBoxSize* toDelete = computedBoxSizes;
    computedBoxSizes = computedBoxSizes->next;
    delete toDelete;
  }

  if (childResized) {
    // See if one of our children forced us to get bigger
    nsRect tmpClientRect(originalClientRect);
    nsMargin bp(0, 0, 0, 0);
    aBox->GetXULBorderAndPadding(bp);
    tmpClientRect.Inflate(bp);

    if (tmpClientRect.width > originalSize.width ||
        tmpClientRect.height > originalSize.height) {
      // if it did reset our bounds.
      nsRect bounds(aBox->GetRect());
      if (tmpClientRect.width > originalSize.width)
        bounds.width = tmpClientRect.width;

      if (tmpClientRect.height > originalSize.height)
        bounds.height = tmpClientRect.height;

      aBox->SetXULBounds(aState, bounds);
    }
  }

  // Because our size grew, we now have to readjust because of box packing.
  // Repack in order to update our x and y to the correct values.
  HandleBoxPack(aBox, frameState, x, y, originalClientRect, clientRect);

  // Compare against our original x and y and only worry about adjusting the
  // children if we really did have to change the positions because of packing
  // (typically for 'center' or 'end' pack values).
  if (x != origX || y != origY) {
    // reposition all our children
    for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
      nsIFrame* child = iter->get();
      nsRect childRect(child->GetRect());
      childRect.x += (x - origX);
      childRect.y += (y - origY);
      child->SetXULBounds(aState, childRect);
    }
  }

  // Perform out-of-axis alignment for non-stretch alignments
  if (!(frameState & NS_STATE_AUTO_STRETCH)) {
    AlignChildren(aBox, aState);
  }

  // That's it!  If you made it this far without having a nervous breakdown,
  // congratulations!  Go get yourself a beer.
  return NS_OK;
}

void nsSprocketLayout::PopulateBoxSizes(nsIFrame* aBox,
                                        nsBoxLayoutState& aState,
                                        nsBoxSize*& aBoxSizes,
                                        nscoord& aMinSize, nscoord& aMaxSize,
                                        int32_t& aFlexes) {
  aMinSize = 0;
  aMaxSize = NS_UNCONSTRAINEDSIZE;

  bool isHorizontal;

  if (IsXULHorizontal(aBox))
    isHorizontal = true;
  else
    isHorizontal = false;

  // this is a nice little optimization
  // it turns out that if we only have 1 flexable child
  // then it does not matter what its preferred size is
  // there is nothing to flex it relative. This is great
  // because we can avoid asking for a preferred size in this
  // case. Why is this good? Well you might have html inside it
  // and asking html for its preferred size is rather expensive.
  // so we can just optimize it out this way.

  // set flexes
  aFlexes = 0;
  nsBoxSize* currentBox = aBoxSizes;
  nsBoxSize* last = nullptr;

  nscoord maxFlex = 0;
  int32_t childCount = 0;

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();
    while (currentBox && currentBox->bogus) {
      last = currentBox;
      currentBox = currentBox->next;
    }
    ++childCount;
    nsSize pref(0, 0);
    nsSize minSize(0, 0);
    nsSize maxSize(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);
    bool collapsed = child->IsXULCollapsed();

    if (!collapsed) {
      // only one flexible child? Cool we will just make its preferred size
      // 0 then and not even have to ask for it.
      // if (flexes != 1)  {

      pref = child->GetXULPrefSize(aState);
      minSize = child->GetXULMinSize(aState);
      maxSize =
          nsIFrame::XULBoundsCheckMinMax(minSize, child->GetXULMaxSize(aState));
      child->GetXULBoxAscent(aState);
      //}

      pref = nsIFrame::XULBoundsCheck(minSize, pref, maxSize);

      AddXULMargin(child, pref);
      AddXULMargin(child, minSize);
      AddXULMargin(child, maxSize);
    }

    if (!currentBox) {
      // create one.
      currentBox = new (aState) nsBoxSize();
      if (!aBoxSizes) {
        aBoxSizes = currentBox;
        last = aBoxSizes;
      } else {
        last->next = currentBox;
        last = currentBox;
      }

      nscoord minWidth;
      nscoord maxWidth;
      nscoord prefWidth;

      // get sizes from child
      if (isHorizontal) {
        minWidth = minSize.width;
        maxWidth = maxSize.width;
        prefWidth = pref.width;
      } else {
        minWidth = minSize.height;
        maxWidth = maxSize.height;
        prefWidth = pref.height;
      }

      nscoord flex = child->GetXULFlex();

      // set them if you collapsed you are not flexible.
      if (collapsed) {
        currentBox->flex = 0;
      } else {
        if (flex > maxFlex) {
          maxFlex = flex;
        }
        currentBox->flex = flex;
      }

      currentBox->pref = prefWidth;
      currentBox->min = minWidth;
      currentBox->max = maxWidth;

      NS_ASSERTION(minWidth <= prefWidth && prefWidth <= maxWidth,
                   "Bad min, pref, max widths!");
    }

    if (!isHorizontal) {
      if (minSize.width > aMinSize) aMinSize = minSize.width;

      if (maxSize.width < aMaxSize) aMaxSize = maxSize.width;

    } else {
      if (minSize.height > aMinSize) aMinSize = minSize.height;

      if (maxSize.height < aMaxSize) aMaxSize = maxSize.height;
    }

    currentBox->collapsed = collapsed;
    aFlexes += currentBox->flex;

    last = currentBox;
    currentBox = currentBox->next;
  }

  if (childCount > 0) {
    nscoord maxAllowedFlex = nscoord_MAX / childCount;

    if (MOZ_UNLIKELY(maxFlex > maxAllowedFlex)) {
      // clamp all the flexes
      currentBox = aBoxSizes;
      while (currentBox) {
        currentBox->flex = std::min(currentBox->flex, maxAllowedFlex);
        currentBox = currentBox->next;
      }
    }
  }
#ifdef DEBUG
  else {
    NS_ASSERTION(maxFlex == 0, "How did that happen?");
  }
#endif
}

void nsSprocketLayout::ComputeChildsNextPosition(
    nsIFrame* aBox, const nscoord& aCurX, const nscoord& aCurY, nscoord& aNextX,
    nscoord& aNextY, const nsRect& aCurrentChildSize) {
  // Get the position along the box axis for the child.
  // The out-of-axis position is not set.
  nsFrameState frameState = nsFrameState(0);
  GetFrameState(aBox, frameState);

  if (IsXULHorizontal(aBox)) {
    // horizontal box's children.
    if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
      aNextX = aCurX + aCurrentChildSize.width;
    else
      aNextX = aCurX - aCurrentChildSize.width;

  } else {
    // vertical box's children.
    if (frameState & NS_STATE_IS_DIRECTION_NORMAL)
      aNextY = aCurY + aCurrentChildSize.height;
    else
      aNextY = aCurY - aCurrentChildSize.height;
  }
}

void nsSprocketLayout::AlignChildren(nsIFrame* aBox, nsBoxLayoutState& aState) {
  nsFrameState frameState = nsFrameState(0);
  GetFrameState(aBox, frameState);
  bool isHorizontal = (frameState & NS_STATE_IS_HORIZONTAL) != 0;
  nsRect clientRect;
  aBox->GetXULClientRect(clientRect);

  MOZ_ASSERT(!(frameState & NS_STATE_AUTO_STRETCH),
             "Only AlignChildren() with non-stretch alignment");

  // These are only calculated if needed
  nsIFrame::Halignment halign;
  nsIFrame::Valignment valign;
  nscoord maxAscent = 0;
  bool isLTR;

  if (isHorizontal) {
    valign = aBox->GetXULVAlign();
    if (valign == nsBoxFrame::vAlign_BaseLine) {
      maxAscent = aBox->GetXULBoxAscent(aState);
    }
  } else {
    isLTR = GetFrameDirection(aBox) == StyleDirection::Ltr;
    halign = aBox->GetXULHAlign();
  }

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();
    nsMargin margin;
    child->GetXULMargin(margin);
    nsRect childRect = child->GetRect();

    if (isHorizontal) {
      const nscoord startAlign = clientRect.y + margin.top;
      const nscoord endAlign =
          clientRect.YMost() - margin.bottom - childRect.height;

      nscoord y = 0;
      switch (valign) {
        case nsBoxFrame::vAlign_Top:
          y = startAlign;
          break;
        case nsBoxFrame::vAlign_Middle:
          // Should this center the border box?
          // This centers the margin box, the historical behavior.
          y = (startAlign + endAlign) / 2;
          break;
        case nsBoxFrame::vAlign_Bottom:
          y = endAlign;
          break;
        case nsBoxFrame::vAlign_BaseLine:
          // Alignments don't force the box to grow (only sizes do),
          // so keep the children within the box.
          y = maxAscent - child->GetXULBoxAscent(aState);
          y = std::max(startAlign, y);
          y = std::min(y, endAlign);
          break;
      }

      childRect.y = y;

    } else {  // vertical box
      const nscoord leftAlign = clientRect.x + margin.left;
      const nscoord rightAlign =
          clientRect.XMost() - margin.right - childRect.width;

      nscoord x = 0;
      switch (halign) {
        case nsBoxFrame::hAlign_Left:  // start
          x = isLTR ? leftAlign : rightAlign;
          break;
        case nsBoxFrame::hAlign_Center:
          x = (leftAlign + rightAlign) / 2;
          break;
        case nsBoxFrame::hAlign_Right:  // end
          x = isLTR ? rightAlign : leftAlign;
          break;
      }

      childRect.x = x;
    }

    if (childRect.TopLeft() != child->GetPosition()) {
      child->SetXULBounds(aState, childRect);
    }
  }
}

void nsSprocketLayout::ChildResized(
    nsIFrame* aBox, nsBoxLayoutState& aState, nsIFrame* aChild,
    nsBoxSize* aChildBoxSize, nsComputedBoxSize* aChildComputedSize,
    nsBoxSize* aBoxSizes, nsComputedBoxSize* aComputedBoxSizes,
    const nsRect& aChildLayoutRect, nsRect& aChildActualRect,
    nsRect& aContainingRect, int32_t aFlexes, bool& aFinished)

{
  nsRect childCurrentRect(aChildLayoutRect);

  bool isHorizontal = IsXULHorizontal(aBox);
  nscoord childLayoutWidth = GET_WIDTH(aChildLayoutRect, isHorizontal);
  nscoord& childActualWidth = GET_WIDTH(aChildActualRect, isHorizontal);
  nscoord& containingWidth = GET_WIDTH(aContainingRect, isHorizontal);

  // nscoord childLayoutHeight = GET_HEIGHT(aChildLayoutRect,isHorizontal);
  nscoord& childActualHeight = GET_HEIGHT(aChildActualRect, isHorizontal);
  nscoord& containingHeight = GET_HEIGHT(aContainingRect, isHorizontal);

  bool recompute = false;

  // if we are a horizontal box see if the child will fit inside us.
  if (childActualHeight > containingHeight) {
    // if we are a horizontal box and the child is bigger than our height

    // ok if the height changed then we need to reflow everyone but us at the
    // new height so we will set the changed index to be us. And signal that we
    // need a new pass.

    nsSize min = aChild->GetXULMinSize(aState);
    nsSize max =
        nsIFrame::XULBoundsCheckMinMax(min, aChild->GetXULMaxSize(aState));
    AddXULMargin(aChild, max);

    if (isHorizontal)
      childActualHeight =
          max.height < childActualHeight ? max.height : childActualHeight;
    else
      childActualHeight =
          max.width < childActualHeight ? max.width : childActualHeight;

    // only set if it changes
    if (childActualHeight > containingHeight) {
      containingHeight = childActualHeight;

      // remember we do not need to clear the resized list because changing the
      // height of a horizontal box will not affect the width of any of its
      // children because block flow left to right, top to bottom. Just trust me
      // on this one.
      aFinished = false;

      // only recompute if there are flexes.
      if (aFlexes > 0) {
        // relayout everything
        recompute = true;
        InvalidateComputedSizes(aComputedBoxSizes);
        nsComputedBoxSize* node = aComputedBoxSizes;

        while (node) {
          node->resized = false;
          node = node->next;
        }
      }
    }
  }

  if (childActualWidth > childLayoutWidth) {
    nsSize min = aChild->GetXULMinSize(aState);
    nsSize max =
        nsIFrame::XULBoundsCheckMinMax(min, aChild->GetXULMaxSize(aState));

    AddXULMargin(aChild, max);

    // our width now becomes the new size

    if (isHorizontal)
      childActualWidth =
          max.width < childActualWidth ? max.width : childActualWidth;
    else
      childActualWidth =
          max.height < childActualWidth ? max.height : childActualWidth;

    if (childActualWidth > childLayoutWidth) {
      aChildComputedSize->size = childActualWidth;
      aChildBoxSize->min = childActualWidth;
      if (aChildBoxSize->pref < childActualWidth)
        aChildBoxSize->pref = childActualWidth;
      if (aChildBoxSize->max < childActualWidth)
        aChildBoxSize->max = childActualWidth;

      // if we have flexible elements with us then reflex things. Otherwise we
      // can skip doing it.
      if (aFlexes > 0) {
        InvalidateComputedSizes(aComputedBoxSizes);

        nsComputedBoxSize* node = aComputedBoxSizes;
        aChildComputedSize->resized = true;

        while (node) {
          if (node->resized) node->valid = true;

          node = node->next;
        }

        recompute = true;
        aFinished = false;
      } else {
        containingWidth += aChildComputedSize->size - childLayoutWidth;
      }
    }
  }

  if (recompute)
    ComputeChildSizes(aBox, aState, containingWidth, aBoxSizes,
                      aComputedBoxSizes);

  if (!childCurrentRect.IsEqualInterior(aChildActualRect)) {
    // the childRect includes the margin
    // make sure we remove it before setting
    // the bounds.
    nsMargin margin(0, 0, 0, 0);
    aChild->GetXULMargin(margin);
    nsRect rect(aChildActualRect);
    if (rect.width >= margin.left + margin.right &&
        rect.height >= margin.top + margin.bottom)
      rect.Deflate(margin);

    aChild->SetXULBounds(aState, rect);
    aChild->XULLayout(aState);
  }
}

void nsSprocketLayout::InvalidateComputedSizes(
    nsComputedBoxSize* aComputedBoxSizes) {
  while (aComputedBoxSizes) {
    aComputedBoxSizes->valid = false;
    aComputedBoxSizes = aComputedBoxSizes->next;
  }
}

void nsSprocketLayout::ComputeChildSizes(
    nsIFrame* aBox, nsBoxLayoutState& aState, nscoord& aGivenSize,
    nsBoxSize* aBoxSizes, nsComputedBoxSize*& aComputedBoxSizes) {
  // nscoord onePixel = aState.PresContext()->IntScaledPixelsToTwips(1);

  int32_t sizeRemaining = aGivenSize;
  int32_t spacerConstantsRemaining = 0;

  // ----- calculate the spacers constants and the size remaining -----

  if (!aComputedBoxSizes) aComputedBoxSizes = new (aState) nsComputedBoxSize();

  nsBoxSize* boxSizes = aBoxSizes;
  nsComputedBoxSize* computedBoxSizes = aComputedBoxSizes;
  int32_t count = 0;
  int32_t validCount = 0;

  while (boxSizes) {
    NS_ASSERTION(
        (boxSizes->min <= boxSizes->pref && boxSizes->pref <= boxSizes->max),
        "bad pref, min, max size");

    // ignore collapsed children
    //  if (boxSizes->collapsed)
    //  {
    //  computedBoxSizes->valid = true;
    //  computedBoxSizes->size = boxSizes->pref;
    // validCount++;
    //      boxSizes->flex = 0;
    // }// else {

    if (computedBoxSizes->valid) {
      sizeRemaining -= computedBoxSizes->size;
      validCount++;
    } else {
      if (boxSizes->flex == 0) {
        computedBoxSizes->valid = true;
        computedBoxSizes->size = boxSizes->pref;
        validCount++;
      }

      spacerConstantsRemaining += boxSizes->flex;
      sizeRemaining -= boxSizes->pref;
    }

    sizeRemaining -= (boxSizes->left + boxSizes->right);

    //}

    boxSizes = boxSizes->next;

    if (boxSizes && !computedBoxSizes->next)
      computedBoxSizes->next = new (aState) nsComputedBoxSize();

    computedBoxSizes = computedBoxSizes->next;
    count++;
  }

  // everything accounted for?
  if (validCount < count) {
    // ----- Ok we are give a size to fit into so stretch or squeeze to fit
    // ----- Make sure we look at our min and max size
    bool limit = true;
    while (limit) {
      limit = false;
      boxSizes = aBoxSizes;
      computedBoxSizes = aComputedBoxSizes;

      while (boxSizes) {
        // ignore collapsed spacers

        //    if (!boxSizes->collapsed) {

        nscoord pref = 0;
        nscoord max = NS_UNCONSTRAINEDSIZE;
        nscoord min = 0;
        nscoord flex = 0;

        pref = boxSizes->pref;
        min = boxSizes->min;
        max = boxSizes->max;
        flex = boxSizes->flex;

        // ----- look at our min and max limits make sure we aren't too small or
        // too big -----
        if (!computedBoxSizes->valid) {
          int32_t newSize = pref + int32_t(int64_t(sizeRemaining) * flex /
                                           spacerConstantsRemaining);

          if (newSize <= min) {
            computedBoxSizes->size = min;
            computedBoxSizes->valid = true;
            spacerConstantsRemaining -= flex;
            sizeRemaining += pref;
            sizeRemaining -= min;
            limit = true;
          } else if (newSize >= max) {
            computedBoxSizes->size = max;
            computedBoxSizes->valid = true;
            spacerConstantsRemaining -= flex;
            sizeRemaining += pref;
            sizeRemaining -= max;
            limit = true;
          }
        }
        // }
        boxSizes = boxSizes->next;
        computedBoxSizes = computedBoxSizes->next;
      }
    }
  }

  // ---- once we have removed and min and max issues just stretch us out in the
  // remaining space
  // ---- or shrink us. Depends on the size remaining and the spacer constants
  aGivenSize = 0;
  boxSizes = aBoxSizes;
  computedBoxSizes = aComputedBoxSizes;

  while (boxSizes) {
    // ignore collapsed spacers
    //  if (!(boxSizes && boxSizes->collapsed)) {

    nscoord pref = 0;
    nscoord flex = 0;
    pref = boxSizes->pref;
    flex = boxSizes->flex;

    if (!computedBoxSizes->valid) {
      computedBoxSizes->size = pref + int32_t(int64_t(sizeRemaining) * flex /
                                              spacerConstantsRemaining);
      computedBoxSizes->valid = true;
    }

    aGivenSize += (boxSizes->left + boxSizes->right);
    aGivenSize += computedBoxSizes->size;

    // }

    boxSizes = boxSizes->next;
    computedBoxSizes = computedBoxSizes->next;
  }
}

nsSize nsSprocketLayout::GetXULPrefSize(nsIFrame* aBox,
                                        nsBoxLayoutState& aState) {
  nsSize vpref(0, 0);
  bool isHorizontal = IsXULHorizontal(aBox);

  // run through all the children and get their min, max, and preferred sizes
  // return us the size of the box

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();
    // ignore collapsed children
    if (child->IsXULCollapsed()) {
      continue;
    }
    nsSize pref = child->GetXULPrefSize(aState);
    AddXULMargin(child, pref);
    AddLargestSize(vpref, pref, isHorizontal);
  }

  // now add our border and padding
  AddXULBorderAndPadding(aBox, vpref);

  return vpref;
}

nsSize nsSprocketLayout::GetXULMinSize(nsIFrame* aBox,
                                       nsBoxLayoutState& aState) {
  nsSize minSize(0, 0);
  bool isHorizontal = IsXULHorizontal(aBox);

  // run through all the children and get their min, max, and preferred sizes
  // return us the size of the box

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();

    // ignore collapsed children
    if (child->IsXULCollapsed()) {
      continue;
    }

    nsSize min = child->GetXULMinSize(aState);
    nsSize pref(0, 0);

    // if the child is not flexible then
    // its min size is its pref size.
    if (child->GetXULFlex() == 0) {
      pref = child->GetXULPrefSize(aState);
      if (isHorizontal)
        min.width = pref.width;
      else
        min.height = pref.height;
    }

    AddXULMargin(child, min);
    AddLargestSize(minSize, min, isHorizontal);
  }

  // now add our border and padding
  AddXULBorderAndPadding(aBox, minSize);

  return minSize;
}

nsSize nsSprocketLayout::GetXULMaxSize(nsIFrame* aBox,
                                       nsBoxLayoutState& aState) {
  bool isHorizontal = IsXULHorizontal(aBox);

  nsSize maxSize(NS_UNCONSTRAINEDSIZE, NS_UNCONSTRAINEDSIZE);

  // run through all the children and get their min, max, and preferred sizes
  // return us the size of the box

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();

    // ignore collapsed children
    if (child->IsXULCollapsed()) {
      continue;
    }
    // if completely redefined don't even ask our child for its size.
    nsSize min = child->GetXULMinSize(aState);
    nsSize max =
        nsIFrame::XULBoundsCheckMinMax(min, child->GetXULMaxSize(aState));

    AddXULMargin(child, max);
    AddSmallestSize(maxSize, max, isHorizontal);
  }

  // now add our border and padding
  AddXULBorderAndPadding(aBox, maxSize);

  return maxSize;
}

nscoord nsSprocketLayout::GetAscent(nsIFrame* aBox, nsBoxLayoutState& aState) {
  nscoord vAscent = 0;

  bool isHorizontal = IsXULHorizontal(aBox);

  // run through all the children and get their min, max, and preferred sizes
  // return us the size of the box

  for (auto iter = IterFor(aBox); iter && !iter->AtEnd(); iter->Next()) {
    nsIFrame* child = iter->get();

    // ignore collapsed children
    // if (!child->IsXULCollapsed())
    //{
    // if completely redefined don't even ask our child for its size.
    nscoord ascent = child->GetXULBoxAscent(aState);

    nsMargin margin;
    child->GetXULMargin(margin);
    ascent += margin.top;

    if (isHorizontal) {
      if (ascent > vAscent) vAscent = ascent;
    } else {
      if (vAscent == 0) vAscent = ascent;
    }
    //}

    child = nsIFrame::GetNextXULBox(child);
  }

  nsMargin borderPadding;
  aBox->GetXULBorderAndPadding(borderPadding);

  return vAscent + borderPadding.top;
}

void nsSprocketLayout::SetLargestSize(nsSize& aSize1, const nsSize& aSize2,
                                      bool aIsHorizontal) {
  if (aIsHorizontal) {
    if (aSize1.height < aSize2.height) aSize1.height = aSize2.height;
  } else {
    if (aSize1.width < aSize2.width) aSize1.width = aSize2.width;
  }
}

void nsSprocketLayout::SetSmallestSize(nsSize& aSize1, const nsSize& aSize2,
                                       bool aIsHorizontal) {
  if (aIsHorizontal) {
    if (aSize1.height > aSize2.height) aSize1.height = aSize2.height;
  } else {
    if (aSize1.width > aSize2.width) aSize1.width = aSize2.width;
  }
}

void nsSprocketLayout::AddLargestSize(nsSize& aSize, const nsSize& aSizeToAdd,
                                      bool aIsHorizontal) {
  if (aIsHorizontal)
    AddCoord(aSize.width, aSizeToAdd.width);
  else
    AddCoord(aSize.height, aSizeToAdd.height);

  SetLargestSize(aSize, aSizeToAdd, aIsHorizontal);
}

void nsSprocketLayout::AddCoord(nscoord& aCoord, nscoord aCoordToAdd) {
  if (aCoord != NS_UNCONSTRAINEDSIZE) {
    if (aCoordToAdd == NS_UNCONSTRAINEDSIZE)
      aCoord = aCoordToAdd;
    else
      aCoord += aCoordToAdd;
  }
}
void nsSprocketLayout::AddSmallestSize(nsSize& aSize, const nsSize& aSizeToAdd,
                                       bool aIsHorizontal) {
  if (aIsHorizontal)
    AddCoord(aSize.width, aSizeToAdd.width);
  else
    AddCoord(aSize.height, aSizeToAdd.height);

  SetSmallestSize(aSize, aSizeToAdd, aIsHorizontal);
}

bool nsSprocketLayout::GetDefaultFlex(int32_t& aFlex) {
  aFlex = 0;
  return true;
}

nsComputedBoxSize::nsComputedBoxSize() {
  resized = false;
  valid = false;
  size = 0;
  next = nullptr;
}

nsBoxSize::nsBoxSize() {
  pref = 0;
  min = 0;
  max = NS_UNCONSTRAINEDSIZE;
  collapsed = false;
  left = 0;
  right = 0;
  flex = 0;
  next = nullptr;
  bogus = false;
}

void* nsBoxSize::operator new(size_t sz,
                              nsBoxLayoutState& aState) noexcept(true) {
  return mozilla::AutoStackArena::Allocate(sz);
}

void nsBoxSize::operator delete(void* aPtr, size_t sz) {}

void* nsComputedBoxSize::operator new(size_t sz,
                                      nsBoxLayoutState& aState) noexcept(true) {
  return mozilla::AutoStackArena::Allocate(sz);
}

void nsComputedBoxSize::operator delete(void* aPtr, size_t sz) {}