[LayoutNG] Initial support for the 'vertical-align' property

third_party/WebKit/Source/core/layout/ng/inline/ng_inline_box_state.h

+// Copyright 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef NGInlineBoxState_h
+#define NGInlineBoxState_h
+
+#include "core/CoreExport.h"
+#include "core/layout/ng/inline/ng_line_height_metrics.h"
+#include "core/style/ComputedStyleConstants.h"
+#include "platform/LayoutUnit.h"
+#include "platform/fonts/FontBaseline.h"
+#include "platform/wtf/Vector.h"
+
+namespace blink {
+
+class NGLayoutInlineItem;
+class NGLineBoxFragmentBuilder;
+class NGTextFragmentBuilder;
+
+// Fragments that require the layout position/size of ancestor are packed in
+// this struct.
+struct NGPendingPositions {
+  unsigned fragment_start;
+  unsigned fragment_end;
+  NGLineHeightMetrics metrics;
+  EVerticalAlign vertical_align;
+};
+
+// Represents the current box while NGInlineLayoutAlgorithm performs layout.
+// Used 1) to cache common values for a box, and 2) to layout children that
+// require ancestor position or size.
+struct NGInlineBoxState {
+  unsigned fragment_start;
+  const ComputedStyle* style;
+  NGLineHeightMetrics metrics;
+  NGLineHeightMetrics text_metrics;
+  LayoutUnit text_top;
+  Vector<NGPendingPositions> pending_descendants;
+  bool include_used_fonts = false;
+
+  // Compute text metrics for a box. All text in a box share the same metrics.
+  void ComputeTextMetrics(const NGLayoutInlineItem&, FontBaseline);
+};
+
+// Represents the inline tree structure. This class provides:
+// 1) Allow access to fragments belonging to the current box.
+// 2) Performs layout when the positin/size of a box was computed.
+// 3) Cache common values for a box.
+class NGInlineLayoutStateStack {
+ public:
+  // Initialize the box state stack for a new line.
+  // @return The initial box state for the line.
+  NGInlineBoxState* OnBeginPlaceItems(const ComputedStyle*);
+
+  // Push a box state stack.
+  NGInlineBoxState* OnOpenTag(const NGLayoutInlineItem&,
+                              NGLineBoxFragmentBuilder*,
+                              NGTextFragmentBuilder*);
+
+  // Pop a box state stack.
+  NGInlineBoxState* OnCloseTag(const NGLayoutInlineItem&,
+                               NGLineBoxFragmentBuilder*,
+                               NGInlineBoxState*);
+
+  // Compute all the pending positioning at the end of a line.
+  void OnEndPlaceItems(NGLineBoxFragmentBuilder*);
+
+ private:
+  // End of a box state, either explicitly by close tag, or implicitly at the
+  // end of a line.
+  void EndBoxState(NGInlineBoxState*, NGLineBoxFragmentBuilder*);
+
+  // Compute vertical position for the 'vertical-align' property.
+  // The timing to apply varies by values; some values apply at the layout of
+  // the box was computed. Other values apply when the layout of the parent or
+  // the line box was computed.
+  // https://www.w3.org/TR/CSS22/visudet.html#propdef-vertical-align
+  // https://www.w3.org/TR/css-inline-3/#propdef-vertical-align
+  void ApplyBaselineShift(NGInlineBoxState*, NGLineBoxFragmentBuilder*);
+
+  Vector<NGInlineBoxState, 4> stack_;
+};
+
+}  // namespace blink
+
+#endif  // NGInlineBoxState_h