Aura overlay scrollbars adjust color for dark backgrounds

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 17 matching lines @@
 
 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;
-constexpr SkColor kOverlayScrollbarThumbColor = SK_ColorBLACK;
+constexpr SkColor kOverlayScrollbarThumbDefaultColor = SK_ColorBLACK;
+constexpr SkColor kOverlayScrollbarThumbLightColor = SK_ColorWHITE;
 constexpr SkColor kOverlayScrollbarStrokeColor = SK_ColorWHITE;
 
 SkAlpha ThumbAlphaForState(NativeTheme::State state) {
   bool overlay = IsOverlayScrollbarEnabled();
   switch (state) {
     case NativeTheme::kDisabled:
       return 0x00;
     case NativeTheme::kHovered:
       return overlay ? kOverlayScrollbarAlphaHovered : 0x4D;
     case NativeTheme::kNormal:
@@ skipping 121 matching lines @@
     State state,
     const ScrollbarTrackExtraParams& extra_params,
     const gfx::Rect& rect) const {
   // Overlay Scrollbar should never paint a scrollbar track.
   DCHECK(!IsOverlayScrollbarEnabled());
   SkPaint paint;
   paint.setColor(kTrackColor);
   canvas->drawIRect(gfx::RectToSkIRect(rect), paint);
 }
 
-void NativeThemeAura::PaintScrollbarThumb(SkCanvas* canvas,
-                                          Part part,
-                                          State state,
-                                          const gfx::Rect& rect) const {
+void NativeThemeAura::PaintScrollbarThumb(
+    SkCanvas* canvas,
+    Part part,
+    State state,
+    const gfx::Rect& rect,
+    ScrollbarOverlayColorTheme theme) const {
   // Do not paint if state is disabled.
   if (state == kDisabled)
     return;
 
-  PaintScrollbarThumbStateTransition(canvas, part, state, state, 1.0, rect);
+  PaintScrollbarThumbStateTransition(canvas, part, state, state, 1.0, rect,
+                                     theme);
 }
 
 void NativeThemeAura::PaintScrollbarThumbStateTransition(
     SkCanvas* canvas,
     Part part,
     State start_state,
     State end_state,
     double progress,
-    const gfx::Rect& rect) const {
+    const gfx::Rect& rect,
+    ScrollbarOverlayColorTheme theme) const {
   TRACE_EVENT0("blink", "NativeThemeAura::PaintScrollbarThumbStateTransition");
   gfx::Rect thumb_rect(rect);
   SkColor thumb_color;
   if (IsOverlayScrollbarEnabled()) {
     // In overlay mode, draw a stroke (border).
     constexpr int kStrokeWidth = kOverlayScrollbarStrokeWidth;
     SkAlpha stroke_alpha = gfx::Tween::IntValueBetween(
         progress, ThumbAlphaForState(start_state),
         ThumbAlphaForState(end_state));
     SkPaint paint;
     paint.setColor(SkColorSetA(kOverlayScrollbarStrokeColor, stroke_alpha));

[bokan, 2016/10/21 16:57:14]

You'll need to do the same thing for the stroke color (if the thumb is white,
the stroke outline should be black)

     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);
-    thumb_color = kOverlayScrollbarThumbColor;
+    if (theme == ScrollbarOverlayColorThemeLight)
+      thumb_color = kOverlayScrollbarThumbLightColor;
+    else
+      thumb_color = kOverlayScrollbarThumbDefaultColor;
   } else {
     // If there are no scrollbuttons then provide some padding so that the thumb
     // doesn't touch the top of the track.
     const int kThumbPadding = 2;
     const int extra_padding =
         (scrollbar_button_length() == 0) ? kThumbPadding : 0;
     if (part == NativeTheme::kScrollbarVerticalThumb)
       thumb_rect.Inset(kThumbPadding, extra_padding);
     else
       thumb_rect.Inset(extra_padding, kThumbPadding);
@@ skipping 39 matching lines @@
         // branch return 0 for parts that don't exist or assert NOTREACHED.
         // crbug.com/657159.
         break;
     }
   }
 
   return NativeThemeBase::GetPartSize(part, state, extra);
 }
 
 }  // namespace ui