[WebPayments] Implement state transitions in desktop WebPayments dialog.

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

+// 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.
+
+#include "chrome/browser/ui/views/payments/view_stack.h"
+
+#include "chrome/browser/ui/views/payments/view_stack_state.h"
+#include "ui/views/layout/fill_layout.h"
+
+// Observes the Slide Out state animation and removes the view when it's done
+// being animated, then deletes itself. This takes ownership of the state so
+// it's garanteed to be properly disposed of when the animation is over.
+class SlideOutObserver : public views::BoundsAnimatorObserver {

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

Move to anonymous namespace?

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

Done.

+ public:
+  explicit SlideOutObserver(std::unique_ptr<ViewStackState> state_animating_out)
+    : state_animating_out_(std::move(state_animating_out)) {}
+
+  views::View* GetAnimatedView() {
+    return state_animating_out_->GetView();
+  }
+
+ private:
+  // views::BoundsAnimatorObserver:
+  void OnBoundsAnimatorProgressed(views::BoundsAnimator* animator) override {}
+
+  void OnBoundsAnimatorDone(views::BoundsAnimator* animator) override {
+    animator->RemoveObserver(this);
+    delete this;
+  }
+
+  std::unique_ptr<ViewStackState> state_animating_out_;
+
+  DISALLOW_COPY_AND_ASSIGN(SlideOutObserver);
+};
+
+ViewStack::ViewStack(std::unique_ptr<ViewStackState> initial_state)
+    : slide_in_animator_(new views::BoundsAnimator(this)),
+      slide_out_animator_(new views::BoundsAnimator(this)),
+      can_process_events_within_subtree_(true) {
+  SetLayoutManager(new views::FillLayout());
+
+  state_stack_.push(std::move(initial_state));
+  AddChildView(state_stack_.top()->GetView());
+
+  slide_in_animator_->AddObserver(this);
+  slide_out_animator_->AddObserver(this);
+}
+
+ViewStack::~ViewStack() {
+  // Cancel animations to make sure their observer's OnBoundsAnimatorDone is
+  // called.
+  slide_in_animator_->Cancel();
+  slide_out_animator_->Cancel();
+}
+
+void ViewStack::PushState(std::unique_ptr<ViewStackState> state) {
+  can_process_events_within_subtree_ = false;
+
+  // First add the new view out of bounds since it'll slide in from right to
+  // left.
+  state->GetView()->SetBounds(width(), 0, width(), height());

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

You should call Layout() on the view after changing the bounds.

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

Done.

+
+  AddChildView(state->GetView());
+  // Animate the new view to be right on top of this one.
+  gfx::Rect destination = bounds();
+  destination.set_origin(gfx::Point(0, 0));
+  slide_in_animator_->AnimateViewTo(state->GetView(), destination);
+
+  // Add the new state to the stack so it can be popped later when navigating
+  // back to the previous screen.
+  state_stack_.push(std::move(state));
+}
+
+void ViewStack::PopState() {
+  can_process_events_within_subtree_ = false;
+
+  gfx::Rect destination = bounds();
+  destination.set_origin(gfx::Point(width(), 0));
+
+  // This deletes itself.
+  SlideOutObserver* observer =
+      new SlideOutObserver(std::move(state_stack_.top()));
+  slide_out_animator_->AddObserver(observer);
+
+  state_stack_.pop();
+  DCHECK(!state_stack_.empty()) << "State stack should never be empty";
+
+  slide_out_animator_->AnimateViewTo(observer->GetAnimatedView(), destination);
+}
+
+bool ViewStack::CanProcessEventsWithinSubtree() const {
+  return can_process_events_within_subtree_;
+}
+
+void ViewStack::OnBoundsAnimatorDone(
+    views::BoundsAnimator* animator) {
+  can_process_events_within_subtree_ = true;
+}