Experimental alignment layout manager using state retained in the layout manager

ui/views/layout/align_layout_state.cc

Index: ui/views/layout/align_layout_state.cc
diff --git a/ui/views/layout/align_layout_state.cc b/ui/views/layout/align_layout_state.cc
new file mode 100644
index 0000000000000000000000000000000000000000..8c8eaf2830a862046dc10dc5ce3ecbd122a4ea08
--- /dev/null
+++ b/ui/views/layout/align_layout_state.cc
@@ -0,0 +1,347 @@
+// Copyright (c) 2011 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.
+
+#include "ui/views/layout/align_layout_state.h"
+
+#include "base/logging.h"
+
+namespace views {
+
+// This special value represents the absence of the align attribute.
+static constexpr Align Align_None =
+    static_cast<Align>(static_cast<int>(Align::Content) + 1);
+
+AlignLayoutState::AnchorState::AnchorState()
+    : anchors({Anchor::Top, Anchor::Left}), anchor_basis(0, 0) {}
+
+AlignLayoutState::AnchorState::AnchorState(Anchors anchors)
+    : anchors(anchors), anchor_basis(0, 0) {}
+
+AlignLayoutState::AnchorState::AnchorState(const AnchorState& state)
+    : anchors(state.anchors), anchor_basis(state.anchor_basis) {}
+
+AlignLayoutState::AnchorState::~AnchorState() {}
+
+AlignLayoutState::AlignLayoutState() {}
+
+AlignLayoutState::~AlignLayoutState() {}
+
+void AlignLayoutState::AlignView(View* view, Align align) {
+  AlignMap::iterator pos = align_map_.find(view);
+  if (pos == align_map_.end())
+    align_map_.emplace(std::make_pair(view, align));
+  else
+    pos->second = align;
+  UpdateAnchorAlign(view, align);
+}
+
+void AlignLayoutState::AnchorView(View* view, Anchors anchors) {
+  AnchorMap::iterator pos = anchor_map_.find(view);
+  if (pos == anchor_map_.end())
+    pos = anchor_map_.emplace(std::make_pair(view, AnchorState(anchors))).first;
+  else
+    pos->second.anchors = anchors;
+  UpdateAnchorBasis(view);
+}
+
+void AlignLayoutState::AnchorView(
+    View* view,
+    const std::initializer_list<Anchor>& anchors) {
+  AnchorView(view, Anchors(anchors));
+}
+
+void AlignLayoutState::AlignViews(View* host,
+                                  views::Align align,
+                                  gfx::Rect& contents) {
+  View::Views align_list;
+  for (int i = 0; i < host->child_count(); ++i) {
+    Align child_align;
+    View* child = host->child_at(i);
+    if (child->visible() && FindAlign(child, &child_align)
+            ? child_align == align
+            : align == Align_None) {
+      View::Views::iterator j = align_list.begin();
+      while (j < align_list.end() && !ShouldInsert(child, *j, align))
+        j++;
+      align_list.insert(j, child);
+    }
+  }
+  for (View* child : align_list) {
+    PlaceView(child, align, contents);
+    UpdateAnchorBasis(child);
+  }
+}
+
+bool AlignLayoutState::FindAlign(View* view, Align* align) {
+  AlignMap::iterator pos = align_map_.find(view);
+  if (pos != align_map_.end()) {
+    if (align)
+      *align = pos->second;
+    return true;
+  }
+  return false;
+}
+
+bool AlignLayoutState::FindAlign(const View* view, Align* align) const {
+  return const_cast<AlignLayoutState*>(this)->FindAlign(const_cast<View*>(view),
+                                                        align);
+}
+
+bool AlignLayoutState::FindAnchorState(View* view, AnchorState** state) {
+  AnchorMap::iterator pos = anchor_map_.find(view);
+  if (pos != anchor_map_.end()) {
+    if (state)
+      *state = &pos->second;
+    return true;
+  }
+  return false;
+}
+
+void AlignLayoutState::InternalUpdateAnchorBasis(View* view,
+                                                 AnchorMap::iterator pos) {
+  AnchorState& state = pos->second;
+  gfx::Point center_point = view->bounds().CenterPoint();
+  if (state.anchors.Has(Anchor::Right))
+    if (state.anchors.Has(Anchor::Left))
+      state.anchor_basis.set_x(view->width());
+    else
+      state.anchor_basis.set_x(view->x());
+  else
+    state.anchor_basis.set_x(center_point.x());
+  if (state.anchors.Has(Anchor::Bottom))
+    if (state.anchors.Has(Anchor::Top))
+      state.anchor_basis.set_y(view->height());
+    else
+      state.anchor_basis.set_y(view->y());
+  else
+    state.anchor_basis.set_y(center_point.y());
+}
+
+void AlignLayoutState::Installed(View* host) {
+  last_host_size_ = host->size();
+}
+
+void AlignLayoutState::Layout(View* host) {
+  static const Align alignstyle[] = {
+      views::Align::Top,   views::Align::Bottom,  views::Align::Left,
+      views::Align::Right, views::Align::Content, Align_None};
+  if (ShouldAlign(host)) {
+    gfx::Rect contents = host->GetContentsBounds();
+    for (std::size_t i = 0; i < sizeof(alignstyle) / sizeof(alignstyle[0]); i++)
+      AlignViews(host, alignstyle[i], contents);
+    last_host_size_ = host->size();
+  }
+}
+
+void AlignLayoutState::NoAlignView(View* view) {
+  AlignMap::iterator pos = align_map_.find(view);
+  if (pos != align_map_.end())
+    align_map_.erase(pos);
+}
+
+void AlignLayoutState::NoAnchorView(View* view) {
+  AnchorMap::iterator pos = anchor_map_.find(view);
+  if (pos != anchor_map_.end())
+    anchor_map_.erase(pos);
+}
+
+gfx::Size AlignLayoutState::GetPreferredSize(const View* host) const {
+  return gfx::Size(0, GetPreferredHeightForWidth(host, 0));
+}
+
+int AlignLayoutState::GetPreferredHeightForWidth(const View* host,
+                                                 int width) const {
+  int height = 0;
+  for (int i = 0; i < host->child_count(); ++i) {
+    Align align;
+    const View* child = host->child_at(i);
+    if (child->visible() && FindAlign(child, &align) &&
+        (align == views::Align::Top || align == views::Align::Bottom ||
+         align == views::Align::Content)) {
+      height += child->GetPreferredSize().height();
+    }
+  }
+  return height;
+}
+
+static int MulDiv(int Number, int Numerator, int Denominator) {
+  return static_cast<int>((static_cast<int64_t>(Number) * Numerator) /
+                          Denominator);
+}
+
+void AlignLayoutState::PlaceView(View* view,
+                                 views::Align align,
+                                 gfx::Rect& contents) {
+  AnchorState state;
+  AnchorState* anchor_state = &state;
+  FindAnchorState(view, &anchor_state);
+  if (align == Align_None ||
+      anchor_state->anchors != AnchorContent::AnchorAlign(align)) {
+    if (!last_host_size_.IsEmpty()) {
+      int new_left = view->x();
+      int new_top = view->y();
+      int new_width = view->width();
+      int new_height = view->height();
+      Anchors anchors = anchor_state->anchors;
+      gfx::Size parent_size = view->parent()->GetContentsBounds().size();
+      if (anchors.Has(Anchor::Right))
+        if (anchors.Has(Anchor::Left))
+          new_width = parent_size.width() -
+                      (last_host_size_.width() -
+                       anchor_state->anchor_basis.x());
+        else
+          new_left = parent_size.width() -
+                     (last_host_size_.width() - anchor_state->anchor_basis.x());
+      else if (!anchors.Has(Anchor::Left))
+        new_left = MulDiv(anchor_state->anchor_basis.x(), parent_size.width(),
+                          last_host_size_.width()) -
+                   new_width / 2;
+      if (anchors.Has(Anchor::Bottom))
+        if (anchors.Has(Anchor::Top))
+          new_height = parent_size.height() - (last_host_size_.height() -
+                                               anchor_state->anchor_basis.y());
+        else
+          new_top = parent_size.height() -
+                    (last_host_size_.height() - anchor_state->anchor_basis.y());
+      else if (!anchors.Has(Anchor::Top))
+        new_top = MulDiv(anchor_state->anchor_basis.y(), parent_size.height(),
+                         last_host_size_.height()) -
+                  new_height / 2;
+      view->SetBounds(new_left, new_top, new_width, new_height);
+    }
+    if (align == Align_None)
+      return;
+  }
+  gfx::Size preferred_size = view->GetPreferredSize();
+  if (preferred_size.IsEmpty()) {
+    // TODO(robliao): Remove this once views has a way to handle preferred size
+    //                correctly.
+    preferred_size = view->size();
+  }
+  int new_width = contents.size().width();
+  if (new_width < 0 || align == views::Align::Left ||
+      align == views::Align::Right) {
+    new_width = preferred_size.width();
+  }
+
+  int new_height = contents.size().height();
+  if (new_height < 0 || align == views::Align::Top ||
+      align == views::Align::Bottom)
+    new_height = preferred_size.height();
+  int new_left = contents.x();
+  int new_top = contents.y();
+  switch (align) {
+    case views::Align::Top: {
+      contents.Inset(0, new_height, 0, 0);
+      break;
+    }
+    case views::Align::Bottom: {
+      contents.Inset(0, 0, 0, new_height);
+      new_top = contents.bottom();
+      break;
+    }
+    case views::Align::Left: {
+      contents.Inset(new_width, 0, 0, 0);
+      break;
+    }
+    case views::Align::Right: {
+      contents.Inset(0, 0, new_width, 0);
+      new_left = contents.right();
+      // Fall through
+    }
+    default:
+      break;
+  }
+  view->SetBounds(new_left, new_top, new_width, new_height);
+  // If the view's bounds are constrained in some other manner, this
+  // will ensure the content rect is adjusted based on the actual
+  // size of the view.
+  if (view->width() != new_width || view->height() != new_height) {
+    switch (align) {
+      case views::Align::Top: {
+        contents.set_y(contents.y() - (new_height - view->height()));
+        break;
+      }
+      case views::Align::Bottom: {
+        contents.set_height(contents.height() + (new_height - view->height()));
+        break;
+      }
+      case views::Align::Left: {
+        contents.set_x(contents.x() - (new_width - view->width()));
+        break;
+      }
+      case views::Align::Right: {
+        contents.set_width(contents.width() + (new_width - view->width()));
+        break;
+      }
+      case views::Align::Content: {
+        contents.set_width(contents.width() + (new_width - view->width()));
+        contents.set_height(contents.height() + (new_height - view->width()));
+      }
+    }
+  }
+}
+
+void AlignLayoutState::SetViewBounds(View* view,
+                                     int x,
+                                     int y,
+                                     int width,
+                                     int height) {
+  DCHECK(view);
+  view->SetBounds(x, y, width, height);
+  UpdateAnchorBasis(view);
+}
+
+bool AlignLayoutState::ShouldAlign(View* host) {
+  for (int i = 0; i < host->child_count(); ++i) {
+    View* view = host->child_at(i);
+    if (view->visible() &&
+        (FindAlign(view, nullptr) || FindAnchorState(view, nullptr)))
+      return true;
+  }
+  return false;
+}
+
+bool AlignLayoutState::ShouldInsert(View* child1,
+                                    View* child2,
+                                    Align align) {
+  switch (align) {
+    case views::Align::Top:
+      return child1->y() < child2->y();
+    case views::Align::Bottom:
+      return child1->bounds().bottom() >= child2->bounds().bottom();
+    case views::Align::Left:
+      return child1->x() < child2->x();
+    case views::Align::Right:
+      return child1->bounds().right() >= child2->bounds().right();
+    default:
+      return false;
+  }
+}
+
+void AlignLayoutState::UpdateAnchorAlign(View* view, Align align) {
+  AnchorMap::iterator pos = anchor_map_.find(view);
+  if (pos != anchor_map_.end()) {
+    pos->second.anchors = AnchorContent::AnchorAlign(align);
+    InternalUpdateAnchorBasis(view, pos);
+  }
+}
+
+void AlignLayoutState::UpdateAnchorBasis(View* view) {
+  AnchorMap::iterator pos = anchor_map_.find(view);
+  if (pos != anchor_map_.end() &&
+      pos->second.anchors != Anchors({Anchor::Left, Anchor::Top}))
+    InternalUpdateAnchorBasis(view, pos);
+}
+
+void AlignLayoutState::ViewAdded(View* host, View* view) {
+  UpdateAnchorBasis(view);
+}
+
+void AlignLayoutState::ViewRemoved(View* host, View* view) {
+  NoAlignView(view);
+  NoAnchorView(view);
+}
+
+}  // namespace views