Linux Aura: Fix overlay shadows on notifications

ui/message_center/views/toast_contents_view.cc

 // Copyright (c) 2013 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/message_center/views/toast_contents_view.h"
 
 #include <memory>
 
 #include "base/bind.h"
 #include "base/compiler_specific.h"
@@ skipping 41 matching lines @@
 ToastContentsView::ToastContentsView(
     const std::string& notification_id,
     PopupAlignmentDelegate* alignment_delegate,
     base::WeakPtr<MessagePopupCollection> collection)
     : collection_(collection),
       id_(notification_id),
       is_closing_(false),
       closing_animation_(NULL) {
   DCHECK(alignment_delegate);
   set_notify_enter_exit_on_child(true);
   // Sets the transparent background. Then, when the message view is slid out,

[sky, 2016/10/07 15:21:08]

I'm not familiar enough with this code to know if it's also using a transparent
background. Based on this comment it looks to me as though it is. Could you ask
a more local owner?

[dewittj, 2016/10/07 18:59:26]

+mukai@, the original author

Seems like we aren't actually using an alpha channel per se, but we are sliding
out the content and relying on the fact that the background is transparent. 
Unfortunately I know too little about the mechanics to really know if that's
what we want here.  Can I recommend a little test using
https://tests.peter.sh/notification-generator/ and sliding out the notification
using your finger on a touch device?

If this is about shadows on notifications, it appears that shadows are working
on ToT.  

[Jun Mukai, 2016/10/07 20:46:49]

It's hard for me to remember everything... Sorry.
Probably, the motivation is that the notification card (the content view) is a
slide view
(https://chromium.googlesource.com/chromium/src/+/master/ui/message_center/vie...)
because we want the slide-out behavior even inside of the notification center.
So the slide-out and touch event handling is within the content view, not here.

In that case, when the user swipes finger on the notification popup, only the
content view moves horizontally and fades out -- thus the popup widget itself
has a transparent background to make the popup itself looks like slid out.

   // the whole toast seems to slide although the actual bound of the widget
   // remains. This is hacky but easier to keep the consistency.
   set_background(views::Background::CreateSolidBackground(0, 0, 0, 0));
 
   fade_animation_.reset(new gfx::SlideAnimation(this));
   fade_animation_->SetSlideDuration(kFadeInOutDuration);
 
   CreateWidget(alignment_delegate);
 }
 
@@ skipping 143 matching lines @@
     collection_->DecrementDeferCounter();
 }
 
 // gfx::AnimationDelegate
 void ToastContentsView::AnimationProgressed(const gfx::Animation* animation) {
   if (animation == bounds_animation_.get()) {
     gfx::Rect current(animation->CurrentValueBetween(
         animated_bounds_start_, animated_bounds_end_));
     GetWidget()->SetBounds(current);
   } else if (animation == fade_animation_.get()) {
     GetWidget()->SetOpacity(

[sky, 2016/10/06 21:44:56]

I'm confused, this is changing the opacity. Doesn't that mean we want
translucent?

[Jun Mukai, 2016/10/07 20:46:49]

This is for normal show/disappear animation. The hack of translucent background
above is for user's swipe handling.

It uses normal animation and uses translucency as usual (possibly this should
use normal corewm window animation though. When I wrote this, Windows was not
yet Aura and couldn't rely on corewm).

         static_cast<float>(fade_animation_->GetCurrentValue()));
   }
 }
 
 void ToastContentsView::AnimationEnded(const gfx::Animation* animation) {
   OnBoundsAnimationEndedOrCancelled(animation);
 }
 
 void ToastContentsView::AnimationCanceled(
     const gfx::Animation* animation) {
@@ skipping 121 matching lines @@
     const std::string& notification_id,
     int button_index) {
   if (collection_)
     collection_->ClickOnNotificationButton(notification_id, button_index);
 }
 
 void ToastContentsView::CreateWidget(
     PopupAlignmentDelegate* alignment_delegate) {
   views::Widget::InitParams params(views::Widget::InitParams::TYPE_POPUP);
   params.keep_on_top = true;
-  params.opacity = views::Widget::InitParams::TRANSLUCENT_WINDOW;
+  params.opacity = views::Widget::InitParams::INFER_OPACITY;
   params.delegate = this;
   views::Widget* widget = new views::Widget();
   alignment_delegate->ConfigureWidgetInitParamsForContainer(widget, &params);
   widget->set_focus_on_creation(false);
 
 #if defined(OS_WIN)
   // We want to ensure that this toast always goes to the native desktop,
   // not the Ash desktop (since there is already another toast contents view
   // there.
   if (!params.parent)
     params.native_widget = new views::DesktopNativeWidgetAura(widget);
 #endif
 
   widget->Init(params);
 }
 
 gfx::Rect ToastContentsView::GetClosedToastBounds(gfx::Rect bounds) {
   return gfx::Rect(bounds.x() + bounds.width() - kClosedToastWidth,
                    bounds.y(),
                    kClosedToastWidth,
                    bounds.height());
 }
 
 }  // namespace message_center