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Unified Diff: Source/core/layout/LayoutTableSection.h

Issue 1319453009: Start adding some documentation to LayoutTable (Closed) Base URL: https://chromium.googlesource.com/chromium/blink.git@master
Patch Set: Updated after yummy, yummy review! Created 5 years, 3 months ago
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Index: Source/core/layout/LayoutTableSection.h
diff --git a/Source/core/layout/LayoutTableSection.h b/Source/core/layout/LayoutTableSection.h
index 84f18232946d84b722905c51b3affb497e79be1f..2e7de835a3ef39acf99e3af058dd431ce57e76eb 100644
--- a/Source/core/layout/LayoutTableSection.h
+++ b/Source/core/layout/LayoutTableSection.h
@@ -67,6 +67,37 @@ private:
class LayoutTableCell;
class LayoutTableRow;
+// LayoutTableSection is used to represent table row group (display:
+// table-row-group), header group (display: table-header-group) and footer group
+// (display: table-footer-group).
+//
+// The object holds the internal representation of the rows (m_grid). See
+// recalcCells() below for some extra explanation.
+//
+// A lot of the complexity in this class is related to handling rowspan, colspan
+// or just non-regular tables.
+//
+// Example of rowspan / colspan leading to overlapping cells (rowspan and
+// colspan are overlapping):
+// <table>
+// <tr>
+// <td>first row</td>
+// <td rowspan="2">rowspan</td>
+// </tr>
+// <tr>
+// <td colspan="2">colspan</td>
+// </tr>
+// </table>
+//
+// Example of non-regular table (missing one cell in the first row):
+// <!DOCTYPE html>
+// <table>
+// <tr><td>First row only child.</td></tr>
+// <tr>
+// <td>Second row first child</td>
+// <td>Second row second child</td>
+// </tr>
+// </table>
class CORE_EXPORT LayoutTableSection final : public LayoutBox {
public:
LayoutTableSection(Element*);
@@ -199,6 +230,16 @@ public:
unsigned numRows() const { return m_grid.size(); }
unsigned numColumns() const;
+
+ // recalcCells() is used when we are not sure about the section's structure
+ // and want to do an expensive (but safe) reconstruction of m_grid from
+ // scratch.
+ // An example of this is inserting a new cell in the middle of an existing
+ // row or removing a row.
+ //
+ // Accessing m_grid when m_needsCellRecalc is set is UNSAFE as pointers can
+ // be left dangling. Thus care should be taken in the code to check
+ // m_needsCellRecalc before accessing m_grid.
void recalcCells();
void recalcCellsIfNeeded()
{
@@ -293,10 +334,29 @@ private:
LayoutObjectChildList m_children;
+ // The representation of the rows and their cells (CellStruct).
Vector<RowStruct> m_grid;
+
+ // The logical offset of each row from the top of the section.
+ //
+ // Note that this Vector has one more entry than the number of rows so that
+ // we can keep track of the final size of the section
+ // (m_rowPos[m_grid.size() + 1]).
+ //
+ // To know a row's height at |rowIndex|, use the formula:
+ // m_rowPos[rowIndex + 1] - m_rowPos[rowIndex]
Vector<int> m_rowPos;
- // the current insertion position
+ // The current insertion position in the grid.
+ // The position is used when inserting a new cell into the section to
+ // know where it should be inserted and expand our internal structure.
+ //
+ // The reason for them is that we process cells as we discover them
+ // during parsing or during recalcCells (ie in DOM order). This means
+ // that we can discover changes in the structure later (e.g. due to
+ // colspans, extra cells, ...).
+ //
+ // Do not use outside of recalcCells and addChild.
unsigned m_cCol;
unsigned m_cRow;
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