diff -r 000000000000 -r 6474c204b198 layout/xul/nsListBoxLayout.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/layout/xul/nsListBoxLayout.cpp	Wed Dec 31 06:09:35 2014 +0100
@@ -0,0 +1,212 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* 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/. */
+
+#include "nsListBoxLayout.h"
+
+#include "nsListBoxBodyFrame.h"
+#include "nsBox.h"
+#include "nsBoxLayoutState.h"
+#include "nsIScrollableFrame.h"
+#include "nsIReflowCallback.h"
+#include "nsNameSpaceManager.h"
+#include "nsGkAtoms.h"
+#include "nsContentUtils.h"
+
+nsListBoxLayout::nsListBoxLayout() : nsGridRowGroupLayout()
+{
+}
+
+////////// nsBoxLayout //////////////
+
+nsSize
+nsListBoxLayout::GetPrefSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState)
+{
+  nsSize pref = nsGridRowGroupLayout::GetPrefSize(aBox, aBoxLayoutState);
+
+  nsListBoxBodyFrame* frame = static_cast<nsListBoxBodyFrame*>(aBox);
+  if (frame) {
+    nscoord rowheight = frame->GetRowHeightAppUnits();
+    pref.height = frame->GetRowCount() * rowheight;
+    // Pad the height.
+    nscoord y = frame->GetAvailableHeight();
+    if (pref.height > y && y > 0 && rowheight > 0) {
+      nscoord m = (pref.height-y)%rowheight;
+      nscoord remainder = m == 0 ? 0 : rowheight - m;
+      pref.height += remainder;
+    }
+    if (nsContentUtils::HasNonEmptyAttr(frame->GetContent(), kNameSpaceID_None,
+                                        nsGkAtoms::sizemode)) {
+      nscoord width = frame->ComputeIntrinsicWidth(aBoxLayoutState);
+      if (width > pref.width)
+        pref.width = width;
+    }
+  }
+  return pref;
+}
+
+nsSize
+nsListBoxLayout::GetMinSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState)
+{
+  nsSize minSize = nsGridRowGroupLayout::GetMinSize(aBox, aBoxLayoutState);
+
+  nsListBoxBodyFrame* frame = static_cast<nsListBoxBodyFrame*>(aBox);
+  if (frame) {
+    nscoord rowheight = frame->GetRowHeightAppUnits();
+    minSize.height = frame->GetRowCount() * rowheight;
+    // Pad the height.
+    nscoord y = frame->GetAvailableHeight();
+    if (minSize.height > y && y > 0 && rowheight > 0) {
+      nscoord m = (minSize.height-y)%rowheight;
+      nscoord remainder = m == 0 ? 0 : rowheight - m;
+      minSize.height += remainder;
+    }
+    if (nsContentUtils::HasNonEmptyAttr(frame->GetContent(), kNameSpaceID_None,
+                                        nsGkAtoms::sizemode)) {
+      nscoord width = frame->ComputeIntrinsicWidth(aBoxLayoutState);
+      if (width > minSize.width)
+        minSize.width = width;
+    }
+  }
+  return minSize;
+}
+
+nsSize
+nsListBoxLayout::GetMaxSize(nsIFrame* aBox, nsBoxLayoutState& aBoxLayoutState)
+{
+  nsSize maxSize = nsGridRowGroupLayout::GetMaxSize(aBox, aBoxLayoutState);
+
+  nsListBoxBodyFrame* frame = static_cast<nsListBoxBodyFrame*>(aBox);
+  if (frame) {
+    nscoord rowheight = frame->GetRowHeightAppUnits();
+    maxSize.height = frame->GetRowCount() * rowheight;
+    // Pad the height.
+    nscoord y = frame->GetAvailableHeight();
+    if (maxSize.height > y && y > 0 && rowheight > 0) {
+      nscoord m = (maxSize.height-y)%rowheight;
+      nscoord remainder = m == 0 ? 0 : rowheight - m;
+      maxSize.height += remainder;
+    }
+  }
+  return maxSize;
+}
+
+NS_IMETHODIMP
+nsListBoxLayout::Layout(nsIFrame* aBox, nsBoxLayoutState& aState)
+{
+  return LayoutInternal(aBox, aState);
+}
+
+
+/////////// nsListBoxLayout /////////////////////////
+
+/**
+ * Called to layout our our children. Does no frame construction
+ */
+NS_IMETHODIMP
+nsListBoxLayout::LayoutInternal(nsIFrame* aBox, nsBoxLayoutState& aState)
+{
+  int32_t redrawStart = -1;
+
+  // Get the start y position.
+  nsListBoxBodyFrame* body = static_cast<nsListBoxBodyFrame*>(aBox);
+  if (!body) {
+    NS_ERROR("Frame encountered that isn't a listboxbody!");
+    return NS_ERROR_FAILURE;
+  }
+
+  nsMargin margin;
+
+  // Get our client rect.
+  nsRect clientRect;
+  aBox->GetClientRect(clientRect);
+
+  // Get the starting y position and the remaining available
+  // height.
+  nscoord availableHeight = body->GetAvailableHeight();
+  nscoord yOffset = body->GetYPosition();
+  
+  if (availableHeight <= 0) {
+    bool fixed = (body->GetFixedRowSize() != -1);
+    if (fixed)
+      availableHeight = 10;
+    else
+      return NS_OK;
+  }
+
+  // run through all our currently created children
+  nsIFrame* box = body->GetChildBox();
+
+  // if the reason is resize or initial we must relayout.
+  nscoord rowHeight = body->GetRowHeightAppUnits();
+
+  while (box) {
+    // If this box is dirty or if it has dirty children, we
+    // call layout on it.
+    nsRect childRect(box->GetRect());
+    box->GetMargin(margin);
+    
+    // relayout if we must or we are dirty or some of our children are dirty
+    //   or the client area is wider than us
+    // XXXldb There should probably be a resize check here too!
+    if (NS_SUBTREE_DIRTY(box) || childRect.width < clientRect.width) {
+      childRect.x = 0;
+      childRect.y = yOffset;
+      childRect.width = clientRect.width;
+      
+      nsSize size = box->GetPrefSize(aState);
+      body->SetRowHeight(size.height);
+      
+      childRect.height = rowHeight;
+
+      childRect.Deflate(margin);
+      box->SetBounds(aState, childRect);
+      box->Layout(aState);
+    } else {
+      // if the child did not need to be relayed out. Then its easy.
+      // Place the child by just grabbing its rect and adjusting the y.
+      int32_t newPos = yOffset+margin.top;
+
+      // are we pushing down or pulling up any rows?
+      // Then we may have to redraw everything below the moved 
+      // rows.
+      if (redrawStart == -1 && childRect.y != newPos)
+        redrawStart = newPos;
+
+      childRect.y = newPos;
+      box->SetBounds(aState, childRect);
+    }
+
+    // Ok now the available size gets smaller and we move the
+    // starting position of the next child down some.
+    nscoord size = childRect.height + margin.top + margin.bottom;
+
+    yOffset += size;
+    availableHeight -= size;
+    
+    box = box->GetNextBox();
+  }
+  
+  // We have enough available height left to add some more rows
+  // Since we can't do this during layout, we post a callback
+  // that will be processed after the reflow completes.
+  body->PostReflowCallback();
+    
+  // if rows were pushed down or pulled up because some rows were added
+  // before them then redraw everything under the inserted rows. The inserted
+  // rows will automatically be redrawn because the were marked dirty on insertion.
+  if (redrawStart > -1) {
+    aBox->Redraw(aState);
+  }
+
+  return NS_OK;
+}
+
+// Creation Routines ///////////////////////////////////////////////////////////////////////
+
+already_AddRefed<nsBoxLayout> NS_NewListBoxLayout()
+{
+  nsRefPtr<nsBoxLayout> layout = new nsListBoxLayout();
+  return layout.forget();
+}