Alpha for overlay scrollbars decreased when hovered.

ui/native_theme/native_theme_aura.cc

 // Copyright (c) 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 "ui/native_theme/native_theme_aura.h"
 
 #include <limits>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 14 matching lines @@
 #include "ui/native_theme/overlay_scrollbar_constants_aura.h"
 
 namespace ui {
 
 namespace {
 
 // Constants for painting overlay scrollbars. Other properties needed outside
 // this painting code are defined in overlay_scrollbar_constants_aura.h.
 constexpr int kOverlayScrollbarStrokeWidth = 1;
 constexpr int kOverlayScrollbarMinimumLength = 12;
-constexpr SkAlpha kOverlayScrollbarAlphaNormal = 0x4D;
-constexpr SkAlpha kOverlayScrollbarAlphaHovered = 0x80;
-constexpr SkAlpha kOverlayScrollbarAlphaPressed = 0x80;
-
-// Indexed by ScrollbarOverlayColorTheme.
-constexpr SkColor kOverlayScrollbarThumbColor[] = {SK_ColorBLACK,
-                                                   SK_ColorWHITE};
-constexpr SkColor kOverlayScrollbarStrokeColor[] = {SK_ColorWHITE,
-                                                    SK_ColorBLACK};
 
 const SkColor kTrackColor = SkColorSetRGB(0xF1, 0xF1, 0xF1);
 
 }  // namespace
 
 ////////////////////////////////////////////////////////////////////////////////
 // NativeTheme:
 
 // static
 NativeTheme* NativeTheme::GetInstanceForWeb() {
@@ skipping 133 matching lines @@
     Part part,
     State state,
     const gfx::Rect& rect,
     ScrollbarOverlayColorTheme theme) const {
   // Do not paint if state is disabled.
   if (state == kDisabled)
     return;
 
   TRACE_EVENT0("blink", "NativeThemeAura::PaintScrollbarThumb");
 
+  // Constants used for painting overlay scrollbar thumb.
+  constexpr SkAlpha kOverlayScrollbarFillAlphaNormal = 0x4D;
+  constexpr SkAlpha kOverlayScrollbarFillAlphaHovered = 0x80;
+  constexpr SkAlpha kOverlayScrollbarFillAlphaPressed = 0x80;
+  constexpr SkAlpha kOverlayScrollbarStrokeAlphaNormal = 0x4D;
+  constexpr SkAlpha kOverlayScrollbarStrokeAlphaHovered = 0x58;
+  constexpr SkAlpha kOverlayScrollbarStrokeAlphaPressed = 0x80;
+
+  // Indexed by ScrollbarOverlayColorTheme.
+  constexpr SkColor kOverlayScrollbarThumbColor[] = {SK_ColorBLACK,
+                                                     SK_ColorWHITE};
+  constexpr SkColor kOverlayScrollbarStrokeColor[] = {SK_ColorWHITE,
+                                                      SK_ColorBLACK};
+
   SkAlpha thumb_alpha = SK_AlphaTRANSPARENT;
+  SkAlpha stroke_alpha = SK_AlphaTRANSPARENT;
   const bool overlay = use_overlay_scrollbars_;
   switch (state) {
     case NativeTheme::kDisabled:
       thumb_alpha = SK_AlphaTRANSPARENT;
+      stroke_alpha = SK_AlphaTRANSPARENT;
       break;
     case NativeTheme::kHovered:
-      thumb_alpha = overlay ? kOverlayScrollbarAlphaHovered : 0x4D;
+      thumb_alpha = overlay ? kOverlayScrollbarFillAlphaHovered : 0x4D;
+      stroke_alpha = overlay ? kOverlayScrollbarStrokeAlphaHovered : 0x4D;
       break;
     case NativeTheme::kNormal:
-      thumb_alpha = overlay ? kOverlayScrollbarAlphaNormal : 0x33;
+      thumb_alpha = overlay ? kOverlayScrollbarFillAlphaNormal : 0x33;
+      stroke_alpha = overlay ? kOverlayScrollbarStrokeAlphaNormal : 0x33;
       break;
     case NativeTheme::kPressed:
-      thumb_alpha = overlay ? kOverlayScrollbarAlphaPressed : 0x80;
+      thumb_alpha = overlay ? kOverlayScrollbarFillAlphaPressed : 0x80;
+      stroke_alpha = overlay ? kOverlayScrollbarStrokeAlphaPressed : 0x80;

[Evan Stade, 2016/12/19 16:06:56]

this ternary still doesn't make sense to me because you never use it in the non
overlay case.

[sahel, 2016/12/19 17:57:26]

You are right, it's only used for overlay case. I wanted to do all the alpha
assignments in one part of code with one switch-case.
Done, moved it to overlay specific part of the function. 

       break;
     case NativeTheme::kNumStates:
       NOTREACHED();
       break;
   }
 
   gfx::Rect thumb_rect(rect);
   SkColor thumb_color;
   if (overlay) {
     thumb_color = kOverlayScrollbarThumbColor[theme];
 
     // In overlay mode, draw a stroke (border).
     constexpr int kStrokeWidth = kOverlayScrollbarStrokeWidth;
     SkPaint paint;
     paint.setColor(
-        SkColorSetA(kOverlayScrollbarStrokeColor[theme], thumb_alpha));
+        SkColorSetA(kOverlayScrollbarStrokeColor[theme], stroke_alpha));
     paint.setStyle(SkPaint::kStroke_Style);
     paint.setStrokeWidth(kStrokeWidth);
 
     gfx::RectF stroke_rect(thumb_rect);
     constexpr float kHalfStrokeWidth = kStrokeWidth / 2.f;
     stroke_rect.Inset(kHalfStrokeWidth, kHalfStrokeWidth);
     canvas->drawRect(gfx::RectFToSkRect(stroke_rect), paint);
 
     // Inset the all the edges edges so we fill-in the stroke below.
     thumb_rect.Inset(kStrokeWidth, kStrokeWidth);
@@ skipping 45 matching lines @@
         // scrollbars isn't asking for part sizes that don't exist.
         // crbug.com/657159.
         break;
     }
   }
 
   return NativeThemeBase::GetPartSize(part, state, extra);
 }
 
 }  // namespace ui