Use animated vector icon for app menu notification animation.

ui/views/controls/animated_icon_view.cc

+// Copyright 2017 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/controls/animated_icon_view.h"
+
+#include "ui/compositor/compositor.h"
+#include "ui/gfx/canvas.h"
+#include "ui/gfx/color_palette.h"
+#include "ui/gfx/paint_vector_icon.h"
+#include "ui/views/widget/widget.h"
+
+namespace views {
+
+AnimatedIconView::AnimatedIconView(const gfx::VectorIcon& icon)
+    : icon_(icon),
+      color_(gfx::kPlaceholderColor),
+      duration_(gfx::GetDurationOfAnimation(icon)) {
+  set_can_process_events_within_subtree(false);

[sadrul, 2017/05/23 18:01:14]

Why? Shouldn't this be something the creator of AnimatedIconView decide?

[Evan Stade, 2017/05/23 23:38:42]

I don't think there will be any instances of this class that want it to handle
events, but if so they can change it away from the default.

[sadrul, 2017/05/24 17:35:14]

When you create a View, the default expectation should be that it can receive
events. If the creator does not want the View to receive events, which is
typically the case when one control View embeds other Views (e.g.
|LabelButton::image_|), then the creator should turn the flag off.

[Evan Stade, 2017/05/24 17:47:53]

ok, I will move this to AppMenuButton.

+  UpdateStaticImage();
+}
+
+AnimatedIconView::~AnimatedIconView() {}
+
+void AnimatedIconView::Animate(State target) {
+  SetState(target);
+  start_time_ = base::TimeTicks::Now();
+  if (!IsAnimating())
+    GetWidget()->GetCompositor()->AddAnimationObserver(this);
+}
+
+void AnimatedIconView::SetState(State state) {
+  state_ = state;
+  UpdateStaticImage();
+}
+
+void AnimatedIconView::OnPaint(gfx::Canvas* canvas) {
+  if (!IsAnimating()) {
+    views::ImageView::OnPaint(canvas);

[sadrul, 2017/05/23 18:01:14]

How does this work when the animation ends? (i.e. when does UpdateStaticImage()
get called for the end of the animation?)

[Evan Stade, 2017/05/23 23:38:42]

Animate() calls SetState() calls UpdateStaticImage(). When the animation is over
that image will be visible.

[sadrul, 2017/05/24 17:35:14]

Who is calling Animate(END)? Shouldn't that happen in OnAnimationStep() when
elapsed > duration_?

[Evan Stade, 2017/05/24 17:47:53]

The client is calling it. In this case, AppMenuButton::AnimateIconIfPossible().

Right now, Animate(START) is never called, but when we have buttons that want to
toggle, e.g. a bluetooth icon with or without a strikethrough to indicate
disabled/enabled, this will change.

[sadrul, 2017/05/26 19:44:47]

The client having to track when the animation ends, and explicitly having to
call Animate(END) does not look like a good API. Why can AnimatedIconView() not
do that in OnAnimationStep()?

[Evan Stade, 2017/05/26 20:48:52]

The client doesn't have to do anything when the animation ends. The client is
calling Animation(END) to initiate the animation to the end state.

[sadrul, 2017/05/30 17:06:51]

I see. So I guess I don't quite understand how OnPaint() would do the right
thing at the end of an animation. Consider the following sequence of events:
 . AnimatedIconView is created. It sets the 'static image' to the start state.
 . The client starts animation with Animate(START); The 'static image' is again
set to the start of the animation state.
 . The animation happens, and completes. So IsAnimating() would now return
false.
 . Some damage happens on the view, and OnPaint() is called again.
 . Because it's not animating, it will paint the 'static image', which is the
start-state of the animation, instead of the end-state. This is a bug, right?

I am probably missing something?

[Evan Stade, 2017/05/30 18:53:45]

You would have called Animate(END), not Animate(START). If you called
Animate(START) while already in the initial state, it would jump to the end of
the animation and progress backwards to the start state again.

[sadrul, 2017/05/30 19:48:33]

Aah, yes. That makes sense now. Thanks for explaining.

+    return;
+  }
+
+  auto timestamp = base::TimeTicks::Now();
+  base::TimeDelta elapsed = timestamp - start_time_;
+  if (state_ == END)
+    elapsed = start_time_ + duration_ - timestamp;
+
+  gfx::Rect target_bounds = GetContentsBounds();
+  target_bounds.ClampToCenteredSize(GetImage().size());

[sadrul, 2017/05/23 18:01:14]

Can this use GetImageBounds()?

[Evan Stade, 2017/05/23 23:38:42]

seems so, thanks!

+  canvas->Translate(gfx::Vector2d(target_bounds.OffsetFromOrigin()));

[sadrul, 2017/05/23 18:01:14]

OffsetFromOrigin() already returns a Vector2d, right?

[Evan Stade, 2017/05/23 23:38:42]

Done.

+  gfx::PaintVectorIcon(canvas, icon_, color_, elapsed);
+}
+
+void AnimatedIconView::OnAnimationStep(base::TimeTicks timestamp) {
+  base::TimeDelta elapsed = timestamp - start_time_;
+  if (elapsed > duration_)
+    GetWidget()->GetCompositor()->RemoveAnimationObserver(this);
+
+  SchedulePaint();
+}
+
+void AnimatedIconView::OnCompositingShuttingDown(ui::Compositor* compositor) {}
+
+bool AnimatedIconView::IsAnimating() {
+  return GetWidget()->GetCompositor()->HasAnimationObserver(this);

[sadrul, 2017/05/23 18:01:14]

Can we maintain a flag instead?

[Evan Stade, 2017/05/23 23:38:42]

how's this?

+}
+
+void AnimatedIconView::UpdateStaticImage() {
+  gfx::IconDescription description(
+      icon_, 0, color_, state_ == START ? base::TimeDelta() : duration_,
+      gfx::kNoneIcon);
+  SetImage(gfx::CreateVectorIcon(description));
+}
+
+}  // namespace views