Hover cards: do not show placeholder image if image data is available.

Previously, the placeholder image could be shown for a frame or two
while the hover card is sliding between tabs, while we're waiting for
the uncompressed version of a cached thumbnail image. This change keeps
the old image around instead (leading to a more smooth hover card
transition as a side effect).


Change-Id: Iecc3f7f31616906c7c9a9d9b62cea31b67cf5f50
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1896240Reviewed-by: Caroline Rising <corising@chromium.org>
Commit-Queue: Caroline Rising <corising@chromium.org>
Auto-Submit: Dana Fried <dfried@chromium.org>
Cr-Commit-Position: refs/heads/master@{#712292}

chrome/browser/ui/thumbnails/thumbnail_image.h

@@ -71,6 +71,8 @@ class ThumbnailImage : public base::RefCounted<ThumbnailImage> {
 
   explicit ThumbnailImage(Delegate* delegate);
 
+  bool has_data() const { return data_.get(); }
+
   void AddObserver(Observer* observer);
   void RemoveObserver(Observer* observer);
   bool HasObserver(const Observer* observer) const;

chrome/browser/ui/views/tabs/tab_hover_card_bubble_view.cc

@@ -255,6 +255,7 @@ class TabHoverCardBubbleView::WidgetSlideAnimationDelegate
 
   void AnimationEnded(const gfx::Animation* animation) override {
     desired_anchor_view_ = nullptr;
+    bubble_delegate_->OnHoverCardLanded();
   }
 
   void AnimationCanceled(const gfx::Animation* animation) override {
@@ -411,6 +412,7 @@ void TabHoverCardBubbleView::UpdateAndShow(Tab* tab) {
       !slide_animation_delegate_->is_animating()) {
     widget_->SetBounds(slide_animation_delegate_->CalculateTargetBounds(tab));
     slide_animation_delegate_->SetCurrentBounds();
+    OnHoverCardLanded();
     return;
   }
 
@@ -424,6 +426,7 @@ void TabHoverCardBubbleView::UpdateAndShow(Tab* tab) {
       SetAnchorView(tab);
     widget_->SetBounds(slide_animation_delegate_->CalculateTargetBounds(tab));
     slide_animation_delegate_->SetCurrentBounds();
+    OnHoverCardLanded();
   }
 
   if (!widget_->IsVisible()) {
@@ -599,8 +602,6 @@ void TabHoverCardBubbleView::UpdateCardContent(const Tab* tab) {
 
   // If the preview image feature is not enabled, |preview_image_| will be null.
   if (preview_image_ && preview_image_->GetVisible()) {
-    if (tab->data().thumbnail != thumbnail_image_)
-      ClearPreviewImage();
     RegisterToThumbnailImageUpdates(tab->data().thumbnail);
   }
 }
@@ -609,11 +610,18 @@ void TabHoverCardBubbleView::RegisterToThumbnailImageUpdates(
     scoped_refptr<ThumbnailImage> thumbnail_image) {
   if (thumbnail_image_ == thumbnail_image)
     return;
+
   if (thumbnail_image_) {
     thumbnail_observer_.Remove(thumbnail_image_.get());
     thumbnail_image_.reset();
   }
+
   if (thumbnail_image) {
+    if (!thumbnail_image->has_data())
+      ClearPreviewImage();
+    else
+      waiting_for_decompress_ = true;
+
     thumbnail_image_ = thumbnail_image;
     thumbnail_observer_.Add(thumbnail_image_.get());
     thumbnail_image->RequestThumbnailImage();
@@ -645,6 +653,17 @@ void TabHoverCardBubbleView::ClearPreviewImage() {
     preview_image_->SetBackground(
         views::CreateSolidBackground(background_color));
   }
+
+  waiting_for_decompress_ = false;
+}
+
+void TabHoverCardBubbleView::OnHoverCardLanded() {
+  // If we were waiting for a preview image with data to load, we don't want to
+  // keep showing the old image while hovering on the new tab, so clear it. This
+  // shouldn't happen very often for slide animations, but could on slower
+  // computers.
+  if (waiting_for_decompress_)
+    ClearPreviewImage();
 }
 
 void TabHoverCardBubbleView::OnThumbnailImageAvailable(
@@ -654,6 +673,7 @@ void TabHoverCardBubbleView::OnThumbnailImageAvailable(
   preview_image_->SetImageSize(preview_size);
   preview_image_->SetPreferredSize(preview_size);
   preview_image_->SetBackground(nullptr);
+  waiting_for_decompress_ = false;
 }
 
 base::Optional<gfx::Size> TabHoverCardBubbleView::GetThumbnailSizeHint() const {

chrome/browser/ui/views/tabs/tab_hover_card_bubble_view.h

@@ -83,6 +83,11 @@ class TabHoverCardBubbleView : public views::BubbleDialogDelegateView,
 
   void ClearPreviewImage();
 
+  // Called when a hover card lands on the tab it's supposed to be a preview
+  // for; happens immediately if there is no slide animation, otherwise when the
+  // animation completes.
+  void OnHoverCardLanded();
+
   // ThumbnailImage::Observer:
   void OnThumbnailImageAvailable(gfx::ImageSkia thumbnail_image) override;
   base::Optional<gfx::Size> GetThumbnailSizeHint() const override;
@@ -115,12 +120,13 @@ class TabHoverCardBubbleView : public views::BubbleDialogDelegateView,
   views::Label* domain_label_ = nullptr;
   views::ImageView* preview_image_ = nullptr;
 
-  // Counter used to keey track of the number of tab hover cards seen before a
+  // Counter used to keep track of the number of tab hover cards seen before a
   // tab is selected by mouse press.
   size_t hover_cards_seen_count_ = 0;
   scoped_refptr<ThumbnailImage> thumbnail_image_;
   ScopedObserver<ThumbnailImage, ThumbnailImage::Observer> thumbnail_observer_{
       this};
+  bool waiting_for_decompress_ = false;
 
   base::WeakPtrFactory<TabHoverCardBubbleView> weak_factory_{this};