Repeat footers in paginated context

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

Index: third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
diff --git a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
index 95efd6a7998bde5fe64d5ea338105f0a3f094c00..5092c0119a5f0e427e563f9ced407d17010b7b6a 100644
--- a/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
+++ b/third_party/WebKit/Source/core/layout/LayoutTableSection.cpp
@@ -1232,7 +1232,8 @@ void LayoutTableSection::LayoutRows() {
 }
 
 int LayoutTableSection::PaginationStrutForRow(LayoutTableRow* row,
-                                              LayoutUnit logical_offset) const {
+                                              LayoutUnit logical_offset,
+                                              bool& can_repeat_footer) const {

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

I think calculating can_repeat_footer should be omitted from this method; it
already does enough work.

Since there's only one call site, we could just do it there, rather than
introducing a utility method for it.

   DCHECK(row);
   if (row->GetPaginationBreakability() == kAllowAnyBreaks)
     return 0;
@@ -1244,6 +1245,17 @@ int LayoutTableSection::PaginationStrutForRow(LayoutTableRow* row,
   if (row_logical_height > page_logical_height)
     return 0;
 
+  LayoutTableSection* footer = Table()->Footer();
+  bool footer_wants_to_repeat =
+      footer && footer != this &&
+      footer->GetPaginationBreakability() != kAllowAnyBreaks &&
+      Table()->RowOffsetFromRepeatingHeader() && row->RowIndex();

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

RowOffsetFromRepeatingHeader() suggests that we depend on a repeating header for
a repeating footer to work, but that can't be right, can it?

+  if (footer_wants_to_repeat) {
+    if (row_logical_height + footer->LogicalHeight() <= page_logical_height) {

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

... however, if there *is* a repeating header, we need to add in its height here
in the comparison, don't we?

+      row_logical_height += footer->LogicalHeight();
+    }
+  }
+
   LayoutUnit remaining_logical_height = PageRemainingLogicalHeightForOffset(
       logical_offset, LayoutBlock::kAssociateWithLatterPage);
   if (remaining_logical_height >= row_logical_height)
@@ -1256,6 +1268,10 @@ int LayoutTableSection::PaginationStrutForRow(LayoutTableRow* row,
     // content completely. No point in leaving a page completely blank.
     return 0;
   }
+
+  if (footer && remaining_logical_height >=
+                    (footer->LogicalHeight() - Table()->VBorderSpacing()))
+    can_repeat_footer = true;
   // Table layout parts only work on integers, so we have to round. Round up, to
   // make sure that no fraction ever gets left behind in the previous
   // fragmentainer.
@@ -2051,8 +2067,9 @@ void LayoutTableSection::AdjustRowForPagination(LayoutTableRow& row_object,
                                                 SubtreeLayoutScope& layouter) {
   row_object.SetPaginationStrut(LayoutUnit());
   row_object.SetLogicalHeight(LayoutUnit(LogicalHeightForRow(row_object)));
-  int pagination_strut =
-      PaginationStrutForRow(&row_object, row_object.LogicalTop());
+  bool can_repeat_footer = false;
+  int pagination_strut = PaginationStrutForRow(
+      &row_object, row_object.LogicalTop(), can_repeat_footer);
   bool row_is_at_top_of_column = false;
   LayoutUnit offset_from_top_of_page;
   if (!pagination_strut) {
@@ -2086,6 +2103,16 @@ void LayoutTableSection::AdjustRowForPagination(LayoutTableRow& row_object,
   if (row_is_at_top_of_column && offset_from_top_of_page)
     pagination_strut -= offset_from_top_of_page.ToInt();
 
+  LayoutTableSection* footer = Table()->Footer();
+  if (footer && footer != this && header != this &&
+      footer->GetPaginationBreakability() != kAllowAnyBreaks &&
+      Table()->RowOffsetFromRepeatingHeader() && can_repeat_footer) {

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

Check can_repeat_footer first.

+    unsigned page = FloorToInt((LogicalTop() + row_object.LogicalTop()) /
+                               PageLogicalHeightForOffset(LayoutUnit()));

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

PageLogicalHeightForOffset() may be 0 (initial column balancing pass), so better
check that before doing any of this.

+    Table()->SetPositionOfRepeatingFooterGroupOnPage(
+        page, LogicalTop() + row_object.LogicalTop());

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

Then again, do we really need to allow individual positions for the footer on
each page? Why not just bottom-align it (unless we're at the last page for the
table)? Edge seems to do that.

+  }
+
   // If we have a header group we will paint it at the top of each page,
   // move the rows down to accomodate it.
   if (header && header != this)
@@ -2105,6 +2132,25 @@ void LayoutTableSection::AdjustRowForPagination(LayoutTableRow& row_object,
   row_object.SetLogicalHeight(LayoutUnit(LogicalHeightForRow(row_object)));
 }
 
+bool LayoutTableSection::IsRepeatingFooterGroup() const {
+  if (GetPaginationBreakability() == LayoutBox::kAllowAnyBreaks)

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

LayoutBox:: scope unnecessary.

+    return false;
+  // TODO(rhogan): Should we paint a header repeatedly if it's self-painting?

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

I don't think it's currently possible to have a self painting layer for a table
section. If I'm right, you might as well DCHECK.

+  if (HasSelfPaintingLayer())
+    return false;
+  LayoutUnit page_height = Table()->PageLogicalHeightForOffset(LayoutUnit());

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

If "page" height isn't uniform (e.g. a multicol container nested inside another
fragmentation context), you end up with incorrect heights here. Need to specify
the correct offset instead of LayoutUnit().

+  if (!page_height)
+    return false;
+  if (LogicalHeight() > page_height)
+    return false;
+  // If the first row of the section after the header group doesn't fit on the
+  // page, then don't repeat the header on each page.
+  // See https://drafts.csswg.org/css-tables-3/#repeated-headers
+  if (Table()->Header() && !Table()->Header()->IsRepeatingHeaderGroup())
+    return false;
+  return true;
+}
+
 bool LayoutTableSection::IsRepeatingHeaderGroup() const {
   if (GetPaginationBreakability() == LayoutBox::kAllowAnyBreaks)
     return false;
@@ -2139,6 +2185,17 @@ bool LayoutTableSection::MapToVisualRectInAncestorSpaceInternal(
     VisualRectFlags flags) const {
   if (ancestor == this)
     return true;
+
+  if (Table()->Footer() == this && IsRepeatingFooterGroup()) {
+    transform_state.Flatten();
+    FloatRect rect = transform_state.LastPlanarQuad().BoundingBox();
+    rect.SetHeight(Table()->LogicalHeight());

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

Introducing a lot of duplicated code here (shared with the code below for
repeating headers). Is there a better way?

+    transform_state.SetQuad(FloatQuad(rect));
+    bool mapped = Table()->MapToVisualRectInAncestorSpaceInternal(

[mstensho (USE GERRIT), 2017/04/24 11:57:16]

We here skip the table section, ignoring its position. Why don't we do the same
below, for repeated table headers?

+        ancestor, transform_state, flags);
+    return mapped;
+  }
+
   // Repeating table headers are painted once per fragmentation page/column.
   // This does not go through the regular fragmentation machinery, so we need
   // special code to expand the invalidation rect to contain all positions of