[WebPayments] Implement state transitions in desktop WebPayments dialog.

chrome/browser/ui/views/payments/view_stack.h

+// Copyright 2016 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 CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_
+#define CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_
+
+#include "ui/views/view.h"
+#include "ui/views/animation/bounds_animator.h"
+#include "ui/views/animation/bounds_animator_observer.h"
+
+class ViewStackState;
+
+// This view represents a stack of views that slide in over one another from
+// left to right. It manages the animation of views that are created by
+// ViewStackState instances, as well as the lifetime of those ViewStackStates.
+// To use this class, add it to a view hierarchy, subclass ViewStackState to
+// create the views that can be pushed on the stack and call PushState/PopState
+// to animate views in and out.
+class ViewStack : public views::BoundsAnimatorObserver,
+                  public views::View {
+ public:
+  explicit ViewStack(std::unique_ptr<ViewStackState> initial_state);
+  ~ViewStack() override;
+
+  // Adds a state to the stack and starts animating it in from the right.
+  void PushState(std::unique_ptr<ViewStackState> state);
+
+  // Removes a state from the stack, animates it out of view, and makes sure
+  // it's properly deleted after the animation.
+  void PopState();
+
+  // views::View:
+  // The children of this view must not be able to process events when the views

[sky, 2016/12/12 01:54:32]

do you really want to disable all events when animating, or just events to the
view being animated out?

[anthonyvd, 2016/12/12 17:01:56]

I think we want all events disabled when animating in and out. Considering the
speed of the animation, it's unlikely that the user will try to perform an event
on the view that's not being animated anyways. It'll also prevent accidental
events in a partially obscured view.

Since this attempts to implement some Material Design style behavior, I can run
it past UXers once this lands to see what they think.

+  // are being animated so this returns false when an animation is in progress.
+  bool CanProcessEventsWithinSubtree() const override;
+
+ private:
+  FRIEND_TEST_ALL_PREFIXES(
+      ViewStackTest, TestPopStateRemovesChildViewAndCleansUpState);
+
+  FRIEND_TEST_ALL_PREFIXES(ViewStackTest, TestDeletingViewCleansUpState);
+
+  // Returns the top state of the stack, used in tests.
+  ViewStackState* top() { return state_stack_.top().get(); }
+
+  // views::BoundsAnimatorObserver:
+  void OnBoundsAnimatorProgressed(views::BoundsAnimator* animator) override {}
+  void OnBoundsAnimatorDone(views::BoundsAnimator* animator) override;
+
+  std::stack<std::unique_ptr<ViewStackState>> state_stack_;
+
+  std::unique_ptr<views::BoundsAnimator> slide_in_animator_;
+  std::unique_ptr<views::BoundsAnimator> slide_out_animator_;
+
+  bool can_process_events_within_subtree_;
+
+  DISALLOW_COPY_AND_ASSIGN(ViewStack);
+};
+
+#endif  // CHROME_BROWSER_UI_VIEWS_PAYMENTS_VIEW_STACK_H_