Imported WebKit commit e09a82039aa4273ab318b71122e92d8e5f233525 (http://svn.webkit.org/repository/webkit/trunk@107223)

1 files changed, 62 insertions, 16 deletions

diff --git a/Source/WebCore/rendering/LayoutState.cpp b/Source/WebCore/rendering/LayoutState.cpp
index c59e97002..c9018c599 100644
--- a/Source/WebCore/rendering/LayoutState.cpp
+++ b/Source/WebCore/rendering/LayoutState.cpp
@@ -37,7 +37,7 @@ namespace WebCore {
 
 LayoutState::LayoutState(LayoutState* prev, RenderBox* renderer, const LayoutSize& offset, LayoutUnit pageLogicalHeight, bool pageLogicalHeightChanged, ColumnInfo* columnInfo)
     : m_columnInfo(columnInfo)
-    , m_currentLineGrid(0)
+    , m_lineGrid(0)
     , m_next(prev)
 #ifndef NDEBUG
     , m_renderer(renderer)
@@ -102,6 +102,9 @@ LayoutState::LayoutState(LayoutState* prev, RenderBox* renderer, const LayoutSiz
             m_pageLogicalHeight = 0;
     }
     
+    // Propagate line grid information.
+    propagateLineGridInfo(renderer);
+
     if (!m_columnInfo)
         m_columnInfo = m_next->m_columnInfo;
 
@@ -109,8 +112,8 @@ LayoutState::LayoutState(LayoutState* prev, RenderBox* renderer, const LayoutSiz
     
     m_isPaginated = m_pageLogicalHeight || m_columnInfo;
 
-    // Propagate line grid information.
-    propagateLineGridInfo(renderer);
+    if (lineGrid() && renderer->hasColumns() && renderer->style()->hasInlineColumnAxis())
+        computeLineGridPaginationOrigin(renderer);
 
     // If we have a new grid to track, then add it to our set.
     if (renderer->style()->lineGrid() != RenderStyle::initialLineGrid() && renderer->isBlockFlow())
@@ -125,7 +128,7 @@ LayoutState::LayoutState(LayoutState* prev, RenderFlowThread* flowThread, bool r
     , m_pageLogicalHeight(1) // Use a fake height here. That value is not important, just needs to be non-zero.
     , m_pageLogicalHeightChanged(regionsChanged)
     , m_columnInfo(0)
-    , m_currentLineGrid(0)
+    , m_lineGrid(0)
     , m_next(prev)
 #ifndef NDEBUG
     , m_renderer(flowThread)
@@ -142,7 +145,7 @@ LayoutState::LayoutState(RenderObject* root)
     , m_pageLogicalHeight(0)
     , m_pageLogicalHeightChanged(false)
     , m_columnInfo(0)
-    , m_currentLineGrid(0)
+    , m_lineGrid(0)
     , m_next(0)
 #ifndef NDEBUG
     , m_renderer(root)
@@ -213,34 +216,77 @@ void LayoutState::propagateLineGridInfo(RenderBox* renderer)
     if (!m_next || renderer->isUnsplittableForPagination())
         return;
 
-    m_currentLineGrid = m_next->m_currentLineGrid;
-    m_currentLineGridOffset = m_next->m_currentLineGridOffset;
+    m_lineGrid = m_next->m_lineGrid;
+    m_lineGridOffset = m_next->m_lineGridOffset;
+    m_lineGridPaginationOrigin = m_next->m_lineGridPaginationOrigin;
 }
 
 void LayoutState::establishLineGrid(RenderBlock* block)
 {
     // First check to see if this grid has been established already.
-    if (m_currentLineGrid) {
-        if (m_currentLineGrid->style()->lineGrid() == block->style()->lineGrid())
+    if (m_lineGrid) {
+        if (m_lineGrid->style()->lineGrid() == block->style()->lineGrid())
             return;
-        RenderBlock* currentGrid = m_currentLineGrid;
+        RenderBlock* currentGrid = m_lineGrid;
         for (LayoutState* currentState = m_next; currentState; currentState = currentState->m_next) {
-            if (currentState->m_currentLineGrid == currentGrid)
+            if (currentState->m_lineGrid == currentGrid)
                 continue;
-            currentGrid = currentState->m_currentLineGrid;
+            currentGrid = currentState->m_lineGrid;
             if (!currentGrid)
                 break;
             if (currentGrid->style()->lineGrid() == block->style()->lineGrid()) {
-                m_currentLineGrid = currentGrid;
-                m_currentLineGridOffset = currentState->m_currentLineGridOffset;
+                m_lineGrid = currentGrid;
+                m_lineGridOffset = currentState->m_lineGridOffset;
                 return;
             }
         }
     }
     
     // We didn't find an already-established grid with this identifier. Our render object establishes the grid.
-    m_currentLineGrid = block;
-    m_currentLineGridOffset = m_layoutOffset; 
+    m_lineGrid = block;
+    m_lineGridOffset = m_layoutOffset; 
+}
+
+void LayoutState::computeLineGridPaginationOrigin(RenderBox* renderer)
+{
+    // We need to cache a line grid pagination origin so that we understand how to reset the line grid
+    // at the top of each column.
+    // Get the current line grid and offset.
+    if (!lineGrid() || lineGrid()->style()->writingMode() != renderer->style()->writingMode())
+        return;
+
+    // Get the hypothetical line box used to establish the grid.
+    RootInlineBox* lineGridBox = lineGrid()->lineGridBox();
+    if (!lineGridBox)
+        return;
+    
+    bool isHorizontalWritingMode = lineGrid()->isHorizontalWritingMode();
+
+    LayoutUnit lineGridBlockOffset = isHorizontalWritingMode ? lineGridOffset().height() : lineGridOffset().width();
+
+    // Now determine our position on the grid. Our baseline needs to be adjusted to the nearest baseline multiple
+    // as established by the line box.
+    // FIXME: Need to handle crazy line-box-contain values that cause the root line box to not be considered. I assume
+    // the grid should honor line-box-contain.
+    LayoutUnit gridLineHeight = lineGridBox->lineBottomWithLeading() - lineGridBox->lineTopWithLeading();
+    if (!gridLineHeight)
+        return;
+
+    LayoutUnit firstLineTopWithLeading = lineGridBlockOffset + lineGridBox->lineTopWithLeading();
+    
+    if (isPaginated() && pageLogicalHeight()) {
+        LayoutUnit pageLogicalTop = renderer->isHorizontalWritingMode() ? m_pageOffset.height() : m_pageOffset.width();
+        if (pageLogicalTop > firstLineTopWithLeading) {
+            // Shift to the next highest line grid multiple past the page logical top. Cache the delta
+            // between this new value and the page logical top as the pagination origin.
+            LayoutUnit remainder = (pageLogicalTop - firstLineTopWithLeading) % gridLineHeight;
+            LayoutUnit paginationDelta = gridLineHeight - remainder;
+            if (isHorizontalWritingMode)
+                m_lineGridPaginationOrigin.setHeight(paginationDelta);
+            else
+                m_lineGridPaginationOrigin.setWidth(paginationDelta);
+        }
+    }
 }
 
 } // namespace WebCore