From 6d504711a01e9be34725f9add22cc7aa311cb14f Mon Sep 17 00:00:00 2001
From: wolfbeast <mcwerewolf@wolfbeast.com>
Date: Mon, 16 Mar 2020 09:30:31 +0100
Subject: Issue #1355 - Make addition of cell border display items depend on
 whether they should be drawn.

This reduces the size of display lists for tables by only adding display
list items that are actually going to be visibly drawn, which will help
overall performance of table drawing.
---
 layout/tables/nsTableFrame.cpp | 83 ++++++++++++++++++++++++++++++++++++++++--
 1 file changed, 79 insertions(+), 4 deletions(-)

(limited to 'layout/tables/nsTableFrame.cpp')

diff --git a/layout/tables/nsTableFrame.cpp b/layout/tables/nsTableFrame.cpp
index 4257c9c57..e5a48139a 100644
--- a/layout/tables/nsTableFrame.cpp
+++ b/layout/tables/nsTableFrame.cpp
@@ -1268,6 +1268,74 @@ PaintRowGroupBackgroundByColIdx(nsTableRowGroupFrame* aRowGroup,
   }
 }
 
+static inline bool FrameHasBorder(nsIFrame* f)
+{
+  if (!f->StyleVisibility()->IsVisible()) {
+    return false;
+  }
+
+  if (f->StyleBorder()->HasBorder()) {
+    return true;
+  }
+
+  return false;
+}
+
+void nsTableFrame::CalcHasBCBorders()
+{
+  if (!IsBorderCollapse()) {
+    SetHasBCBorders(false);
+    return;
+  }
+
+  if (FrameHasBorder(this)) {
+    SetHasBCBorders(true);
+    return;
+  }
+
+  // Check col and col group has borders.
+  for (nsIFrame* f : this->GetChildList(kColGroupList)) {
+    if (FrameHasBorder(f)) {
+      SetHasBCBorders(true);
+      return;
+    }
+
+    nsTableColGroupFrame *colGroup = static_cast<nsTableColGroupFrame*>(f);
+    for (nsTableColFrame* col = colGroup->GetFirstColumn(); col; col = col->GetNextCol()) {
+      if (FrameHasBorder(col)) {
+        SetHasBCBorders(true);
+        return;
+      }
+    }
+  }
+
+  // check row group, row and cell has borders.
+  RowGroupArray rowGroups;
+  OrderRowGroups(rowGroups);
+  for (nsTableRowGroupFrame* rowGroup : rowGroups) {
+    if (FrameHasBorder(rowGroup)) {
+      SetHasBCBorders(true);
+      return;
+    }
+
+    for (nsTableRowFrame* row = rowGroup->GetFirstRow(); row; row = row->GetNextRow()) {
+      if (FrameHasBorder(row)) {
+        SetHasBCBorders(true);
+        return;
+      }
+
+      for (nsTableCellFrame* cell = row->GetFirstCell(); cell; cell = cell->GetNextCell()) {
+        if (FrameHasBorder(cell)) {
+          SetHasBCBorders(true);
+          return;
+        }
+      }
+    }
+  }
+
+  SetHasBCBorders(false);
+}
+
 /* static */ void
 nsTableFrame::DisplayGenericTablePart(nsDisplayListBuilder* aBuilder,
                                       nsFrame* aFrame,
@@ -1375,11 +1443,16 @@ nsTableFrame::DisplayGenericTablePart(nsDisplayListBuilder* aBuilder,
       nsTableFrame* table = static_cast<nsTableFrame*>(aFrame);
       // In the collapsed border model, overlay all collapsed borders.
       if (table->IsBorderCollapse()) {
-        aLists.BorderBackground()->AppendNewToTop(
-          new (aBuilder) nsDisplayTableBorderCollapse(aBuilder, table));
+        if (table->HasBCBorders()) {
+          aLists.BorderBackground()->AppendNewToTop(
+            new (aBuilder) nsDisplayTableBorderCollapse(aBuilder, table));
+        }
       } else {
-        aLists.BorderBackground()->AppendNewToTop(
-          new (aBuilder) nsDisplayBorder(aBuilder, table));
+        const nsStyleBorder* borderStyle = aFrame->StyleBorder();
+        if (borderStyle->HasBorder()) {
+          aLists.BorderBackground()->AppendNewToTop(
+            new (aBuilder) nsDisplayBorder(aBuilder, table));
+        }
       }
     }
   }
@@ -4101,6 +4174,7 @@ nsTableFrame::AddBCDamageArea(const TableArea& aValue)
 #endif
 
   SetNeedToCalcBCBorders(true);
+  SetNeedToCalcHasBCBorders(true);
   // Get the property
   BCPropertyData* value = GetOrCreateBCProperty();
   if (value) {
@@ -4141,6 +4215,7 @@ nsTableFrame::SetFullBCDamageArea()
   NS_ASSERTION(IsBorderCollapse(), "invalid SetFullBCDamageArea call");
 
   SetNeedToCalcBCBorders(true);
+  SetNeedToCalcHasBCBorders(true);
 
   BCPropertyData* value = GetOrCreateBCProperty();
   if (value) {
-- 
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