Fix and simplify bookmark bar detach/attach animation.

chrome/browser/ui/views/frame/browser_view.cc

 // Copyright 2012 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/frame/browser_view.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/command_line.h"
@@ skipping 394 matching lines @@
     BookmarkBarView* bookmark_bar_view,
     Browser* browser)
     : browser_view_(browser_view),
       bookmark_bar_view_(bookmark_bar_view),
       browser_(browser) {
 }
 
 void BookmarkBarViewBackground::Paint(gfx::Canvas* canvas,
                                       views::View* view) const {
   int toolbar_overlap = bookmark_bar_view_->GetToolbarOverlap();
-  if (!bookmark_bar_view_->IsDetached()) {
-    PaintAttachedBookmarkBar(canvas,
-                             bookmark_bar_view_,
-                             browser_view_,
-                             browser_->host_desktop_type(),
-                             toolbar_overlap);
-    return;
-  }
 
   // As 'hidden' according to the animation is the full in-tab state, we invert
-  // the value - when current_state is at '0', we expect the bar to be docked.
-  double current_state = 1 - bookmark_bar_view_->GetAnimationValue();
-
-  if (current_state == 0.0 || current_state == 1.0) {
-    PaintDetachedBookmarkBar(canvas, bookmark_bar_view_, browser_->profile());
-    return;
-  }
-  // While animating, set opacity to cross-fade between attached and detached
-  // backgrounds including their respective separators.
-  int detached_alpha = static_cast<uint8>(current_state * 255);
-  int attached_alpha = 255 - detached_alpha;
-  if (browser_->bookmark_bar_state() == BookmarkBar::DETACHED) {
-    // To animate from attached to detached state:
-    // - fade out attached background
-    // - fade in detached background.
-    canvas->SaveLayerAlpha(attached_alpha);
-    PaintAttachedBookmarkBar(canvas,
-                             bookmark_bar_view_,
-                             browser_view_,
-                             browser_->host_desktop_type(),
-                             toolbar_overlap);
-    canvas->Restore();
-    canvas->SaveLayerAlpha(detached_alpha);
-    PaintDetachedBookmarkBar(canvas, bookmark_bar_view_, browser_->profile());
-  } else {
-    // To animate from detached to attached state:
-    // - fade out detached background
-    // - fade in attached background.
-    canvas->SaveLayerAlpha(detached_alpha);
-    PaintDetachedBookmarkBar(canvas, bookmark_bar_view_, browser_->profile());
-    canvas->Restore();
-    canvas->SaveLayerAlpha(attached_alpha);
+  // the value - when detach_percent is at '0', we expect the bar to be docked.
+  double detach_percent = 1 - bookmark_bar_view_->GetAnimationValue();

[Peter Kasting, 2015/12/22 05:52:42]

Nit: Since this is the only callsite for GetAnimationValue(), perhaps that
function should be changed to:

SkAlpha BookmarkBarView::GetAnimationValue() const {
  return static_cast<SkAlpha>(size_animation_->CurrentValueBetween(255, 0));
}

Then the code here simply becomes:

  SkAlpha detached_alpha = bookmark_bar_view_->GetAnimationValue();
  if (detached_alpha < 255) {
    ...
  }
  ...

Nitpicky note: I use SkAlpha instead of uint8 in part because we're trying to
kill uint8 (see Avi's ongoing changes) and in part because SkAlpha, while
typedefed to the same thing, is a more logical and descriptive type for alpha
values, and I'm hoping to move toward using it directly in the various canvas
APIs.

[Evan Stade, 2015/12/29 17:14:16]

I changed uint8 to SkAlpha and changed BookmarkBarView to expose the animation
directly (since there were a couple of single-use pass throughs that can use
this instead).

+  if (detach_percent != 1.0) {
     PaintAttachedBookmarkBar(canvas,
                              bookmark_bar_view_,
                              browser_view_,
                              browser_->host_desktop_type(),
                              toolbar_overlap);
   }
+
+  if (!bookmark_bar_view_->IsDetached() || detach_percent == 0.0)
+    return;
+
+  // While animating, set opacity to cross-fade between attached and detached
+  // backgrounds including their respective separators.
+  int detached_alpha = static_cast<uint8>(detach_percent * 255);
+  canvas->SaveLayerAlpha(detached_alpha);
+  PaintDetachedBookmarkBar(canvas, bookmark_bar_view_, browser_->profile());
   canvas->Restore();
 }
 
 ///////////////////////////////////////////////////////////////////////////////
 // BrowserView, public:
 
 // static
 const char BrowserView::kViewClassName[] = "BrowserView";
 
 BrowserView::BrowserView()
@@ skipping 2230 matching lines @@
   return immersive_mode_controller()->IsEnabled();
 }
 
 views::Widget* BrowserView::GetBubbleAssociatedWidget() {
   return GetWidget();
 }
 
 gfx::Rect BrowserView::GetTopContainerBoundsInScreen() {
   return top_container_->GetBoundsInScreen();
 }