[EditingNG] Paint caret in NG contenteditable blocks

This patch makes NGBoxFragmentPainter paint caret by
- Routing back to legacy LayoutBlock to determine if a block has
  carets to paint
- Adding caret painting code to NGBoxFragmentPainter
so that carets can be painted in NG contenteditable blocks.

This patch makes other editing NG development/debugging easier.

It also fixes some image failures with EditingNG flag enabled, e.g.
editing/selection/editable-links.html.

Bug: 876555
Cq-Include-Trybots: luci.chromium.try:linux_layout_tests_layout_ng;luci.chromium.try:linux_layout_tests_slimming_paint_v2;master.tryserver.blink:linux_trusty_blink_rel
Change-Id: I29968b24872603d999b8fd2301ffd465cac23406
Reviewed-on: https://chromium-review.googlesource.com/1185499
Commit-Queue: Xiaocheng Hu <xiaochengh@chromium.org>
Reviewed-by: Yoshifumi Inoue <yosin@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Reviewed-by: Yoichi Osato <yoichio@chromium.org>
Cr-Commit-Position: refs/heads/master@{#586309}

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.cc

@@ -4,6 +4,9 @@
 
 #include "third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.h"
 
+#include "third_party/blink/renderer/core/editing/drag_caret.h"
+#include "third_party/blink/renderer/core/editing/frame_selection.h"
+#include "third_party/blink/renderer/core/frame/local_frame.h"
 #include "third_party/blink/renderer/core/layout/background_bleed_avoidance.h"
 #include "third_party/blink/renderer/core/layout/hit_test_location.h"
 #include "third_party/blink/renderer/core/layout/hit_test_result.h"
@@ -17,6 +20,7 @@
 #include "third_party/blink/renderer/core/layout/ng/inline/ng_physical_text_fragment.h"
 #include "third_party/blink/renderer/core/layout/ng/layout_ng_mixin.h"
 #include "third_party/blink/renderer/core/layout/ng/ng_physical_box_fragment.h"
+#include "third_party/blink/renderer/core/page/page.h"
 #include "third_party/blink/renderer/core/paint/background_image_geometry.h"
 #include "third_party/blink/renderer/core/paint/box_decoration_data.h"
 #include "third_party/blink/renderer/core/paint/list_marker_painter.h"
@@ -260,12 +264,25 @@ void NGBoxFragmentPainter::PaintObject(
 
   if (ShouldPaintSelfOutline(paint_phase))
     NGFragmentPainter(box_fragment_).PaintOutline(paint_info, paint_offset);
-  // TODO(layout-dev): Implement once we have selections in LayoutNG.
-  // If the caret's node's layout object's containing block is this block, and
+
+  // If the caret's node's fragment's containing block is this block, and
   // the paint action is PaintPhaseForeground, then paint the caret.
-  // if (paint_phase == PaintPhase::kForeground &&
-  //     box_fragment_.ShouldPaintCarets())
-  //  PaintCarets(paint_info, paint_offset);
+  if (paint_phase == PaintPhase::kForeground &&
+      box_fragment_.ShouldPaintCarets())
+    PaintCarets(paint_info, paint_offset);
+}
+
+void NGBoxFragmentPainter::PaintCarets(const PaintInfo& paint_info,
+                                       const LayoutPoint& paint_offset) {
+  LocalFrame* frame = box_fragment_.GetLayoutObject()->GetFrame();
+
+  if (box_fragment_.ShouldPaintCursorCaret())
+    frame->Selection().PaintCaret(paint_info.context, paint_offset);
+
+  if (box_fragment_.ShouldPaintDragCaret()) {
+    frame->GetPage()->GetDragCaret().PaintDragCaret(frame, paint_info.context,
+                                                    paint_offset);
+  }
 }
 
 void NGBoxFragmentPainter::PaintBlockFlowContents(

third_party/blink/renderer/core/paint/ng/ng_box_fragment_painter.h

@@ -109,6 +109,7 @@ class NGBoxFragmentPainter : public BoxPainterBase {
   void PaintSymbol(const NGPaintFragment&,
                    const PaintInfo&,
                    const LayoutPoint& paint_offset);
+  void PaintCarets(const PaintInfo&, const LayoutPoint& paint_offset);
 
   bool IsInSelfHitTestingPhase(HitTestAction) const;
   bool VisibleToHitTestRequest(const HitTestRequest&) const;

third_party/blink/renderer/core/paint/ng/ng_paint_fragment.cc

@@ -695,6 +695,22 @@ Node* NGPaintFragment::NodeForHitTest() const {
   return nullptr;
 }
 
+bool NGPaintFragment::ShouldPaintCursorCaret() const {
+  // TODO(xiaochengh): Merge cursor caret painting functions from LayoutBlock to
+  // FrameSelection.
+  if (!GetLayoutObject()->IsLayoutBlock())
+    return false;
+  return ToLayoutBlock(GetLayoutObject())->ShouldPaintCursorCaret();
+}
+
+bool NGPaintFragment::ShouldPaintDragCaret() const {
+  // TODO(xiaochengh): Merge drag caret painting functions from LayoutBlock to
+  // DragCaret.
+  if (!GetLayoutObject()->IsLayoutBlock())
+    return false;
+  return ToLayoutBlock(GetLayoutObject())->ShouldPaintDragCaret();
+}
+
 // ----
 
 NGPaintFragment& NGPaintFragment::FragmentRange::front() const {

third_party/blink/renderer/core/paint/ng/ng_paint_fragment.h

@@ -144,6 +144,14 @@ class CORE_EXPORT NGPaintFragment : public DisplayItemClient,
   // from GetNode() when this fragment is content of a pseudo node.
   Node* NodeForHitTest() const;
 
+  // Utility functions for caret painting. Note that carets are painted as part
+  // of the containing block's foreground.
+  bool ShouldPaintCursorCaret() const;
+  bool ShouldPaintDragCaret() const;
+  bool ShouldPaintCarets() const {
+    return ShouldPaintCursorCaret() || ShouldPaintDragCaret();
+  }
+
   // A range of fragments for |FragmentsFor()|.
   class CORE_EXPORT FragmentRange {
    public: