Repeat footers in paginated context

third_party/WebKit/Source/core/layout/LayoutTable.cpp

 /*
  * Copyright (C) 1997 Martin Jones (mjones@kde.org)
  *           (C) 1997 Torben Weis (weis@kde.org)
  *           (C) 1998 Waldo Bastian (bastian@kde.org)
  *           (C) 1999 Lars Knoll (knoll@kde.org)
  *           (C) 1999 Antti Koivisto (koivisto@kde.org)
  * Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2013 Apple Inc.
  *               All rights reserved.
  * Copyright (C) 2006 Alexey Proskuryakov (ap@nypop.com)
  *
@@ skipping 629 matching lines @@
     }
     LayoutUnit current_available_logical_height =
         AvailableLogicalHeight(kIncludeMarginBorderPadding);
     TableHeightChangingValue table_height_changing =
         old_available_logical_height_ && old_available_logical_height_ !=
                                              current_available_logical_height
             ? kTableHeightChanging
             : kTableHeightNotChanging;
     old_available_logical_height_ = current_available_logical_height;
 
+    // Lay out table footer to get its raw height. This will help us decide
+    // if we can repeat it in each page/column.
+    if (LayoutTableSection* section = Footer()) {
+      if (section->GetPaginationBreakability() != kAllowAnyBreaks) {
+        section->LayoutIfNeeded();
+        int section_logical_height = section->CalcRowLogicalHeight();
+        section->SetLogicalHeight(LayoutUnit(section_logical_height));
+      }
+      section->DetermineIfFooterGroupShouldRepeat();
+      if (section->IsRepeatingFooterGroup()) {
+        LayoutUnit offset_for_table_footers =
+            state.HeightOffsetForTableFooters();
+        offset_for_table_footers += section->LogicalHeight();
+        state.SetHeightOffsetForTableFooters(offset_for_table_footers);

[mstensho (USE GERRIT), 2017/06/16 08:43:06]

What if we delay setting this until right before laying out the bodies? Then we
could get rid of the temporary resetting below, couldn't we?

[rhogan, 2017/06/20 18:46:05]

Yup, reorganized this.

+        SetRowOffsetFromRepeatingFooter(offset_for_table_footers);
+      }
+    }
+
     // Lay out table header group.
     if (LayoutTableSection* section = Header()) {
+      // Reset the offset temporarily so that we can ignore it when paginating
+      // the content of the footer itself.
+      LayoutUnit offset_for_table_footers = state.HeightOffsetForTableFooters();
+      state.SetHeightOffsetForTableFooters(LayoutUnit());
       LayoutSection(*section, layouter, section_logical_left,
                     table_height_changing);
+      state.SetHeightOffsetForTableFooters(offset_for_table_footers);
       if (state.IsPaginated() && IsPageLogicalHeightKnown()) {
         // If the repeating header group allows at least one row of content,
         // then store the offset for other sections to offset their rows
         // against.
         if (section->IsRepeatingHeaderGroup()) {
           LayoutUnit offset_for_table_headers =
               state.HeightOffsetForTableHeaders();
           offset_for_table_headers += section->LogicalHeight();
           // Don't include any strut in the header group - we only want the
           // height from its content.
@@ skipping 16 matching lines @@
         }
       } else if (child->IsLayoutTableCol()) {
         child->LayoutIfNeeded();
       } else {
         DCHECK(child->IsTableCaption());
       }
     }
 
     // Lay out table footer.
     if (LayoutTableSection* section = Footer()) {
+      // Reset the offset temporarily so that we can ignore it when paginating
+      // the content of the footer itself.
+      LayoutUnit offset_for_table_footers = state.HeightOffsetForTableFooters();
+      state.SetHeightOffsetForTableFooters(LayoutUnit());

[mstensho (USE GERRIT), 2017/06/16 08:43:06]

No need to temporarily reset this, if you just move it a bit further up. We're
going to set it to LayoutUnit() unconditionally below anyway.

[rhogan, 2017/06/20 18:46:05]

ditto.

       LayoutSection(*section, layouter, section_logical_left,
                     table_height_changing);
+      state.SetHeightOffsetForTableFooters(offset_for_table_footers);
     }
 
+    // We no longer need to account for repeating table headers.
+    state.SetHeightOffsetForTableHeaders(LayoutUnit());

[mstensho (USE GERRIT), 2017/06/16 08:43:06]

I don't think I understand why we need to reset this here. I realize that
LayoutRows() won't do much work if the table crosses fragmentainer boundaries
(and it's only then that we need to worry about repeated headers and footers).
So it won't make much of a difference. But do we HAVE TO reset it?

[rhogan, 2017/06/20 18:46:05]

We don't want layout of the footer sections or captions to know about either of
these which is why we reset them.
single-line-cells-multiple-tables-caption-repeating-thead-tfoot-with-border-spacing-at-top-of-row-4.html
is a test that covers the need to reset the header value,
single-line-cells-multiple-tables-caption-repeating-thead-tfoot-with-border-spacing-at-top-of-row-2.html
(among quite a few) that covers the footer case.

+    state.SetHeightOffsetForTableFooters(LayoutUnit());
+
     SetLogicalHeight(table_box_logical_top + border_and_padding_before);
 
     LayoutUnit computed_logical_height = LogicalHeightFromStyle();
     LayoutUnit total_section_logical_height;
     if (top_section) {
       total_section_logical_height =
           bottom_section->LogicalBottom() - top_section->LogicalTop();
     }
 
     if (!state.IsPaginated() ||
@@ skipping 908 matching lines @@
   collapsed_outer_borders_valid_ = true;
   if (ShouldCollapseBorders()) {
     collapsed_outer_border_before_ = ComputeCollapsedOuterBorderBefore();
     collapsed_outer_border_after_ = ComputeCollapsedOuterBorderAfter();
     collapsed_outer_border_start_ = ComputeCollapsedOuterBorderStart();
     collapsed_outer_border_end_ = ComputeCollapsedOuterBorderEnd();
   }
 }
 
 }  // namespace blink