Experimental alignment layout manager using a property on the views

ui/views/layout/align_layout.cc

+// 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.h"
+
+#include "base/logging.h"
+#include "ui/views/anchor_attribute.h"
+
+namespace views {
+
+// This special value represents the absence of the align attribute.
+static constexpr Fill Fill_None =
+    static_cast<Fill>(static_cast<int>(Fill::Content) + 1);
+
+AlignLayout::AlignLayout() {}
+
+AlignLayout::~AlignLayout() {}
+
+void AlignLayout::AlignViews(View* host,
+                             views::Fill fill,
+                             gfx::Rect& contents) {
+  View::Views fill_list;
+  for (int i = 0; i < host->child_count(); ++i) {
+    FillAttribute* fill_attr;
+    View* child = host->child_at(i);
+    if (child->visible() && child->attributes().Find(fill_attr)
+            ? fill_attr->fill() == fill
+            : fill == Fill_None) {
+      View::Views::iterator j = fill_list.begin();
+      while (j < fill_list.end() && !ShouldInsert(child, *j, fill))
+        j++;
+      fill_list.insert(j, child);
+    }
+  }
+  for (View* child : fill_list)
+    PlaceView(child, fill, contents);
+}
+
+void AlignLayout::Layout(View* host) {
+  static const Fill fillstyles[] = {
+      views::Fill::Top,   views::Fill::Bottom,  views::Fill::Left,
+      views::Fill::Right, views::Fill::Content, Fill_None};
+  if (ShouldAlign(host)) {
+    gfx::Rect contents = host->GetContentsBounds();
+    for (std::size_t i = 0; i < sizeof(fillstyles) / sizeof(fillstyles[0]); i++)
+      AlignViews(host, fillstyles[i], contents);
+  }
+}
+
+gfx::Size AlignLayout::GetPreferredSize(const View* host) const {
+  return gfx::Size();
+}
+
+int AlignLayout::GetPreferredHeightForWidth(const View* host, int width) const {
+  return 0;
+}
+
+static int MulDiv(int Number, int Numerator, int Denominator) {
+  return static_cast<int>((static_cast<int64_t>(Number) * Numerator) /
+                          Denominator);
+}
+
+void AlignLayout::PlaceView(View* view,
+                            views::Fill fill,
+                            gfx::Rect& contents) {
+  AnchorAttribute* anchor = nullptr;
+  AnchorContent local_content;
+  AnchorContent& content =
+      view->attributes().Find(anchor) ? anchor->GetContent() : local_content;
+  if (fill == Fill_None ||
+      content.anchors() != AnchorContent::AnchorFill(fill)) {
+    if (!content.LastParentSize().IsEmpty()) {
+      int new_left = view->x();
+      int new_top = view->y();
+      int new_width = view->width();
+      int new_height = view->height();
+      Anchors anchors = content.anchors();
+      gfx::Size parent_size = view->parent()->GetContentsBounds().size();
+      if (anchors.Contains(Anchor::Right))
+        if (anchors.Contains(Anchor::Left))
+          new_width = parent_size.width() - (content.LastParentSize().width() -
+                                             content.anchorBasis().x());
+        else
+          new_left = parent_size.width() - (content.LastParentSize().width() -
+                                            content.anchorBasis().x());
+      else if (!anchors.Contains(Anchor::Left))
+        new_left = MulDiv(content.anchorBasis().x(), parent_size.width(),
+                          content.LastParentSize().width()) -
+                   new_width / 2;
+      if (anchors.Contains(Anchor::Bottom))
+        if (anchors.Contains(Anchor::Top))
+          new_height =
+              parent_size.height() -
+              (content.LastParentSize().height() - content.anchorBasis().y());
+        else
+          new_top = parent_size.height() - (content.LastParentSize().height() -
+                                            content.anchorBasis().y());
+      else if (!anchors.Contains(Anchor::Top))
+        new_top = MulDiv(content.anchorBasis().y(), parent_size.height(),
+                         content.LastParentSize().height()) -
+                  new_height / 2;
+      view->SetBounds(new_left, new_top, new_width, new_height);
+    }
+    if (fill == Fill_None)
+      return;
+  }
+  int new_width = contents.size().width();
+  if (new_width < 0 || fill == views::Fill::Left ||
+      fill == views::Fill::Right)
+    new_width = view->width();
+  int new_height = contents.size().height();
+  if (new_height < 0 || fill == views::Fill::Top ||
+      fill == views::Fill::Bottom)
+    new_height = view->height();
+  int new_left = contents.x();
+  int new_top = contents.y();
+  switch (fill) {
+    case views::Fill::Top: {
+      contents.Inset(0, new_height, 0, 0);
+      break;
+    }
+    case views::Fill::Bottom: {
+      contents.Inset(0, 0, 0, new_height);
+      new_top = contents.bottom();
+      break;
+    }
+    case views::Fill::Left: {
+      contents.Inset(new_width, 0, 0, 0);
+      break;
+    }
+    case views::Fill::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 (fill) {
+      case views::Fill::Top: {
+        contents.set_y(contents.y() - (new_height - view->height()));
+        break;
+      }
+      case views::Fill::Bottom: {
+        contents.set_height(contents.height() + (new_height - view->height()));
+        break;
+      }
+      case views::Fill::Left: {
+        contents.set_x(contents.x() - (new_width - view->width()));
+        break;
+      }
+      case views::Fill::Right: {
+        contents.set_width(contents.width() + (new_width - view->width()));
+        break;
+      }
+      case views::Fill::Content: {
+        contents.set_width(contents.width() + (new_width - view->width()));
+        contents.set_height(contents.height() + (new_height - view->width()));
+      }
+    }
+  }
+}
+
+bool AlignLayout::ShouldAlign(View* host) {
+  for (int i = 0; i < host->child_count(); ++i) {
+    FillAttribute* fill_attr;
+    AnchorAttribute* anchor_attr;
+    View* view = host->child_at(i);
+    if (view->visible() && (view->attributes().Find(fill_attr) ||
+                            view->attributes().Find(anchor_attr)))
+      return true;
+  }
+  return false;
+}
+
+bool AlignLayout::ShouldInsert(View* child1, View* child2, views::Fill fill) {
+  switch (fill) {
+    case views::Fill::Top:
+      return child1->y() < child2->y();
+    case views::Fill::Bottom:
+      return child1->bounds().bottom() >= child2->bounds().bottom();
+    case views::Fill::Left:
+      return child1->x() < child2->x();
+    case views::Fill::Right:
+      return child1->bounds().right() >= child2->bounds().right();
+    default:
+      return false;
+  }
+}
+
+}  // namespace views