Restore elevation to holding space tray icon previews.

Per UX request, restoring slight elevation to holding space tray icon
previews to add depth and dilineation.

This CL also makes a slight tweak to shrinking of white backgrounds
that was done to prevent paint artifacts from showing behind images.
Previously we shrunk backgrounds by twice as much as was necessary.

Bug: 1163304
Change-Id: I1b65bb65de3e331f2e58c2993fe1634d5dabcb98
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2618560Reviewed-by: Toni Baržić <tbarzic@chromium.org>
Commit-Queue: David Black <dmblack@google.com>
Cr-Commit-Position: refs/heads/master@{#841669}

ash/system/holding_space/holding_space_drag_util.cc

@@ -159,8 +159,8 @@ class DragImageItemView : public views::View {
     // painting the background outside content bounds as might otherwise occur
     // due to pixel rounding. Failure to do so could result in white paint
     // artifacts.
-    gfx::Rect bounds(GetContentsBounds());
-    bounds.Inset(gfx::Insets(1));
+    gfx::RectF bounds(GetContentsBounds());
+    bounds.Inset(gfx::InsetsF(0.5f));
 
     cc::PaintFlags flags;
     flags.setAntiAlias(true);

ash/system/holding_space/holding_space_item_chip_view.cc

@@ -4,6 +4,8 @@
 
 #include "ash/system/holding_space/holding_space_item_chip_view.h"
 
+#include <algorithm>
+
 #include "ash/public/cpp/holding_space/holding_space_constants.h"
 #include "ash/public/cpp/holding_space/holding_space_item.h"
 #include "ash/public/cpp/rounded_image_view.h"
@@ -17,9 +19,41 @@
 #include "ui/views/layout/box_layout.h"
 #include "ui/views/layout/fill_layout.h"
 #include "ui/views/metadata/metadata_impl_macros.h"
+#include "ui/views/painter.h"
 
 namespace ash {
 
+// CirclePainter ---------------------------------------------------------------
+
+class CirclePainter : public views::Painter {
+ public:
+  CirclePainter(SkColor color, const gfx::InsetsF& insets)
+      : color_(color), insets_(insets) {}
+  CirclePainter(const CirclePainter&) = delete;
+  CirclePainter& operator=(const CirclePainter&) = delete;
+  ~CirclePainter() override = default;
+
+ private:
+  // views::Painter:
+  gfx::Size GetMinimumSize() const override { return gfx::Size(); }
+
+  void Paint(gfx::Canvas* canvas, const gfx::Size& size) override {
+    gfx::RectF bounds{gfx::SizeF(size)};
+    bounds.Inset(insets_);
+
+    cc::PaintFlags flags;
+    flags.setAntiAlias(true);
+    flags.setColor(color_);
+
+    canvas->DrawCircle(
+        bounds.CenterPoint(),
+        std::min(bounds.size().width(), bounds.size().height()) / 2.f, flags);
+  }
+
+  const SkColor color_;
+  const gfx::InsetsF insets_;
+};
+
 // HoldingSpaceItemChipView::LabelMaskOwner ------------------------------------
 
 class HoldingSpaceItemChipView::LabelMaskLayerOwner : public ui::LayerDelegate {
@@ -88,8 +122,12 @@ HoldingSpaceItemChipView::HoldingSpaceItemChipView(
 
   image_ = AddChildView(std::make_unique<RoundedImageView>(
       kHoldingSpaceChipIconSize / 2, RoundedImageView::Alignment::kLeading));
-  image_->SetBackground(views::CreateRoundedRectBackground(
-      SK_ColorWHITE, kHoldingSpaceChipIconSize / 2));
+
+  // Shrink circular background by a single pixel to prevent painting outside of
+  // the image which may otherwise occur due to pixel rounding. Failure to do so
+  // could result in white paint artifacts.
+  image_->SetBackground(views::CreateBackgroundFromPainter(
+      std::make_unique<CirclePainter>(SK_ColorWHITE, gfx::InsetsF(0.5f))));
 
   // Subscribe to be notified of changes to `item_`'s image.
   image_subscription_ =

ash/system/holding_space/holding_space_tray_icon_preview.cc

@@ -4,6 +4,8 @@
 
 #include "ash/system/holding_space/holding_space_tray_icon_preview.h"
 
+#include <algorithm>
+
 #include "ash/public/cpp/holding_space/holding_space_constants.h"
 #include "ash/public/cpp/holding_space/holding_space_image.h"
 #include "ash/public/cpp/holding_space/holding_space_item.h"
@@ -20,12 +22,16 @@
 #include "ui/gfx/image/image_skia.h"
 #include "ui/gfx/image/image_skia_operations.h"
 #include "ui/gfx/image/image_skia_source.h"
+#include "ui/gfx/shadow_util.h"
 #include "ui/gfx/skia_paint_util.h"
 
 namespace ash {
 
 namespace {
 
+// Appearance.
+constexpr int kElevation = 1;
+
 // The duration of each of the preview icon bounce animation.
 constexpr base::TimeDelta kBounceAnimationSegmentDuration =
     base::TimeDelta::FromMilliseconds(250);
@@ -47,6 +53,13 @@ gfx::Size GetPreviewSize() {
                    kHoldingSpaceTrayIconPreviewSize);
 }
 
+// Returns the shadow details for painting elevation.
+const gfx::ShadowDetails& GetShadowDetails() {
+  const gfx::Size size(GetPreviewSize());
+  const int radius = std::min(size.height(), size.width()) / 2;
+  return gfx::ShadowDetails::Get(kElevation, radius);
+}
+
 // Returns whether the specified `shelf_alignment` is horizontal.
 bool IsHorizontal(ShelfAlignment shelf_alignment) {
   switch (shelf_alignment) {
@@ -307,13 +320,16 @@ void HoldingSpaceTrayIconPreview::OnPaintLayer(
   cc::PaintFlags flags;
   flags.setAntiAlias(true);
   flags.setColor(SK_ColorWHITE);
+  flags.setLooper(gfx::CreateShadowDrawLooper(GetShadowDetails().values));
   canvas->DrawCircle(
-      contents_bounds.CenterPoint(),
-      std::min(contents_bounds.width(), contents_bounds.height()) / 2 - 1,
+      gfx::PointF(contents_bounds.CenterPoint()),
+      std::min(contents_bounds.width(), contents_bounds.height()) / 2 - 0.5,
       flags);
 
   // Contents.
+  // NOTE: The `contents_image_` should already be resized.
   if (!contents_image_.isNull()) {
+    DCHECK_EQ(contents_image_.size(), contents_bounds.size());
     canvas->DrawImageInt(contents_image_, contents_bounds.x(),
                          contents_bounds.y());
   }