Move CalculateScrollbarModes from FrameView to LayoutView.

third_party/WebKit/Source/core/paint/PaintLayerScrollableArea.cpp

 /*
  * Copyright (C) 2006, 2007, 2008, 2009, 2010, 2011, 2012 Apple Inc. All rights
  * reserved.
  *
  * Portions are Copyright (C) 1998 Netscape Communications Corporation.
  *
  * Other contributors:
  *   Robert O'Callahan <roc+@cs.cmu.edu>
  *   David Baron <dbaron@fas.harvard.edu>
  *   Christian Biesinger <cbiesinger@gmail.com>
@@ skipping 647 matching lines @@
     if (FrameView* frame_view = frame->View())
       frame_view->RemoveAnimatingScrollableArea(this);
   }
 }
 
 bool PaintLayerScrollableArea::UserInputScrollable(
     ScrollbarOrientation orientation) const {
   if (Box().IsIntrinsicallyScrollable(orientation))
     return true;
 
   if (Box().IsLayoutView()) {

[szager1, 2017/05/22 18:29:35]

General observation: we should probably work towards eliminating calls to
Box().IsLayoutView(), and instead delegate to virtual methods defined on
LayoutBox.  UserInputScrollable is a good candidate, because its logic doesn't
use any information from PLSA, it's all from Box().

No need to do anything for this patch, just a suggestion going forward.

[skobes, 2017/05/22 19:15:10]

Agreed.  Scrollability is a big mess right now with lots of near redundancy and
similar-sounding methods that do different things.  I initially thought of
making CalculateScrollbarModes virtual on LayoutBox, but in that case it should
probably take on the rest of the logic currently in
PLSA::ComputeScrollbarExistence and replace other LayoutBox APIs like
ScrollsOverflow{X,Y} and HasAuto{Horizontal,Vertical}Scrollbar... it was looking
like a huge ball of yarn to untangle so I backed off from that idea.  Would be
nice to clean it all up somehow.

-    if (LocalFrame* frame = Box().GetFrame()) {
-      if (FrameView* frame_view = frame->View()) {
-        ScrollbarMode h_mode;
-        ScrollbarMode v_mode;
-        frame_view->CalculateScrollbarModes(h_mode, v_mode);
-        if (orientation == kHorizontalScrollbar &&
-            h_mode == kScrollbarAlwaysOff)
-          return false;
-        if (orientation == kVerticalScrollbar && v_mode == kScrollbarAlwaysOff)
-          return false;
-      }
-    }
+    ScrollbarMode h_mode;
+    ScrollbarMode v_mode;
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
+    if (orientation == kHorizontalScrollbar && h_mode == kScrollbarAlwaysOff)
+      return false;
+    if (orientation == kVerticalScrollbar && v_mode == kScrollbarAlwaysOff)
+      return false;
   }
 
   EOverflow overflow_style = (orientation == kHorizontalScrollbar)
                                  ? Box().Style()->OverflowX()
                                  : Box().Style()->OverflowY();
   return (overflow_style == EOverflow::kScroll ||
           overflow_style == EOverflow::kAuto ||
           overflow_style == EOverflow::kOverlay);
 }
 
@@ skipping 593 matching lines @@
         Box().IsRooted() && this->HasVerticalOverflow() &&
         Box().PixelSnappedClientWidth() + Box().VerticalScrollbarWidth() > 0;
   }
 
   // Look for the scrollbarModes and reset the needs Horizontal & vertical
   // Scrollbar values based on scrollbarModes, as during force style change
   // StyleResolver::styleForDocument returns documentStyle with no overflow
   // values, due to which we are destroying the scrollbars that were already
   // present.
   if (Box().IsLayoutView()) {
-    if (LocalFrame* frame = Box().GetFrame()) {
-      if (FrameView* frame_view = frame->View()) {
-        ScrollbarMode h_mode;
-        ScrollbarMode v_mode;
-        frame_view->CalculateScrollbarModes(h_mode, v_mode);
-        if (h_mode == kScrollbarAlwaysOn)
-          needs_horizontal_scrollbar = true;
-        else if (h_mode == kScrollbarAlwaysOff)
-          needs_horizontal_scrollbar = false;
-        if (v_mode == kScrollbarAlwaysOn)
-          needs_vertical_scrollbar = true;
-        else if (v_mode == kScrollbarAlwaysOff)
-          needs_vertical_scrollbar = false;
-      }
-    }
+    ScrollbarMode h_mode;
+    ScrollbarMode v_mode;
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
+    if (h_mode == kScrollbarAlwaysOn)
+      needs_horizontal_scrollbar = true;
+    else if (h_mode == kScrollbarAlwaysOff)
+      needs_horizontal_scrollbar = false;
+    if (v_mode == kScrollbarAlwaysOn)
+      needs_vertical_scrollbar = true;
+    else if (v_mode == kScrollbarAlwaysOff)
+      needs_vertical_scrollbar = false;
   }
 }
 
 bool PaintLayerScrollableArea::SetHasHorizontalScrollbar(bool has_scrollbar) {
   if (FreezeScrollbarsScope::ScrollbarsAreFrozen())
     return false;
 
   if (has_scrollbar == HasHorizontalScrollbar())
     return false;
 
@@ skipping 454 matching lines @@
 
   FrameView* frame_view = frame->View();
   if (!frame_view)
     return;
 
   bool is_visible_to_hit_test = Box().Style()->VisibleToHitTesting();
   bool did_scroll_overflow = scrolls_overflow_;
   if (Box().IsLayoutView()) {
     ScrollbarMode h_mode;
     ScrollbarMode v_mode;
-    frame_view->CalculateScrollbarModes(h_mode, v_mode);
+    ToLayoutView(Box()).CalculateScrollbarModes(h_mode, v_mode);
     if (h_mode == kScrollbarAlwaysOff && v_mode == kScrollbarAlwaysOff)
       has_overflow = false;
   }
   scrolls_overflow_ = has_overflow && is_visible_to_hit_test;
   if (did_scroll_overflow == ScrollsOverflow())
     return;
 
   if (RuntimeEnabledFeatures::slimmingPaintInvalidationEnabled()) {
     // The scroll and scroll offset properties depend on |scrollsOverflow| (see:
     // PaintPropertyTreeBuilder::updateScrollAndScrollTranslation).
@@ skipping 400 matching lines @@
 
 void PaintLayerScrollableArea::DelayScrollOffsetClampScope::
     ClampScrollableAreas() {
   for (auto& scrollable_area : *needs_clamp_)
     scrollable_area->ClampScrollOffsetAfterOverflowChange();
   delete needs_clamp_;
   needs_clamp_ = nullptr;
 }
 
 }  // namespace blink