Use refs for non-null GraphicsContext, Scrollbar, etc. in scrollbar related code

third_party/WebKit/Source/platform/scroll/ScrollbarThemeMacCommon.mm

 /*
  * Copyright (C) 2008, 2011 Apple Inc. All Rights Reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 51 matching lines @@
 {
     DEFINE_STATIC_LOCAL(ScrollbarSet, set, ());
     return set;
 }
 
 static float gInitialButtonDelay = 0.5f;
 static float gAutoscrollButtonDelay = 0.05f;
 static NSScrollerStyle gPreferredScrollerStyle = NSScrollerStyleLegacy;
 static bool gScrollAnimationEnabledForSystem = false;
 
-ScrollbarTheme* ScrollbarTheme::nativeTheme()
+ScrollbarTheme& ScrollbarTheme::nativeTheme()
 {
-    static ScrollbarThemeMacCommon* theme = NULL;
-    if (theme)
-        return theme;
     if (ScrollbarThemeMacCommon::isOverlayAPIAvailable()) {
         DEFINE_STATIC_LOCAL(ScrollbarThemeMacOverlayAPI, overlayTheme, ());
-        theme = &overlayTheme;
-    } else {
+        return overlayTheme;
+    }
+    {
         DEFINE_STATIC_LOCAL(ScrollbarThemeMacNonOverlayAPI, nonOverlayTheme, ());
-        theme = &nonOverlayTheme;
+        return nonOverlayTheme;
     }
-    return theme;
 }
 
-void ScrollbarThemeMacCommon::registerScrollbar(ScrollbarThemeClient* scrollbar)
+void ScrollbarThemeMacCommon::registerScrollbar(ScrollbarThemeClient& scrollbar)
 {
-    scrollbarSet().add(scrollbar);
+    scrollbarSet().add(&scrollbar);
 }
 
-void ScrollbarThemeMacCommon::unregisterScrollbar(ScrollbarThemeClient* scrollbar)
+void ScrollbarThemeMacCommon::unregisterScrollbar(ScrollbarThemeClient& scrollbar)
 {
-    scrollbarSet().remove(scrollbar);
+    scrollbarSet().remove(&scrollbar);
 }
 
-void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const ScrollbarThemeClient* scrollbar, const IntRect& rect, const Vector<IntRect>& tickmarks)
+void ScrollbarThemeMacCommon::paintGivenTickmarks(SkCanvas* canvas, const ScrollbarThemeClient& scrollbar, const IntRect& rect, const Vector<IntRect>& tickmarks)
 {
-    if (scrollbar->orientation() != VerticalScrollbar)
+    if (scrollbar.orientation() != VerticalScrollbar)
         return;
 
     if (rect.height() <= 0 || rect.width() <= 0)
         return;  // nothing to draw on.
 
     if (!tickmarks.size())
         return;
 
     SkAutoCanvasRestore stateSaver(canvas, true);
 
     SkPaint strokePaint;
     strokePaint.setAntiAlias(false);
     strokePaint.setColor(SkColorSetRGB(0xCC, 0xAA, 0x00));
     strokePaint.setStyle(SkPaint::kStroke_Style);
 
     SkPaint fillPaint;
     fillPaint.setAntiAlias(false);
     fillPaint.setColor(SkColorSetRGB(0xFF, 0xDD, 0x00));
     fillPaint.setStyle(SkPaint::kFill_Style);
 
     for (Vector<IntRect>::const_iterator i = tickmarks.begin(); i != tickmarks.end(); ++i) {
         // Calculate how far down (in %) the tick-mark should appear.
-        const float percent = static_cast<float>(i->y()) / scrollbar->totalSize();
+        const float percent = static_cast<float>(i->y()) / scrollbar.totalSize();
         if (percent < 0.0 || percent > 1.0)
             continue;
 
         // Calculate how far down (in pixels) the tick-mark should appear.
         const int yPos = rect.y() + (rect.height() * percent);
 
         // Paint.
         FloatRect tickRect(rect.x(), yPos, rect.width(), 2);
         canvas->drawRect(tickRect, fillPaint);
         canvas->drawRect(tickRect, strokePaint);
     }
 }
 
-void ScrollbarThemeMacCommon::paintTickmarks(GraphicsContext* context, const ScrollbarThemeClient* scrollbar, const IntRect& rect)
+void ScrollbarThemeMacCommon::paintTickmarks(GraphicsContext& context, const ScrollbarThemeClient& scrollbar, const IntRect& rect)
 {
     // Note: This is only used for css-styled scrollbars on mac.
-    if (scrollbar->orientation() != VerticalScrollbar)
+    if (scrollbar.orientation() != VerticalScrollbar)
         return;
 
     if (rect.height() <= 0 || rect.width() <= 0)
         return;
 
     Vector<IntRect> tickmarks;
-    scrollbar->getTickmarks(tickmarks);
+    scrollbar.getTickmarks(tickmarks);
     if (!tickmarks.size())
         return;
 
-    if (DrawingRecorder::useCachedDrawingIfPossible(*context, *scrollbar, DisplayItem::ScrollbarTickmarks))
+    if (DrawingRecorder::useCachedDrawingIfPossible(context, scrollbar, DisplayItem::ScrollbarTickmarks))
         return;
 
-    DrawingRecorder recorder(*context, *scrollbar, DisplayItem::ScrollbarTickmarks, rect);
+    DrawingRecorder recorder(context, scrollbar, DisplayItem::ScrollbarTickmarks, rect);
 
     // Inset a bit.
     IntRect tickmarkTrackRect = rect;
     tickmarkTrackRect.setX(tickmarkTrackRect.x() + 1);
     tickmarkTrackRect.setWidth(tickmarkTrackRect.width() - 2);
-    paintGivenTickmarks(context->canvas(), scrollbar, tickmarkTrackRect, tickmarks);
+    paintGivenTickmarks(context.canvas(), scrollbar, tickmarkTrackRect, tickmarks);
 }
 
 ScrollbarThemeMacCommon::~ScrollbarThemeMacCommon()
 {
 }
 
 void ScrollbarThemeMacCommon::preferencesChanged(float initialButtonDelay, float autoscrollButtonDelay, NSScrollerStyle preferredScrollerStyle, bool redraw, bool scrollAnimationEnabled, ScrollbarButtonsPlacement buttonPlacement)
 {
     updateButtonPlacement(buttonPlacement);
     gInitialButtonDelay = initialButtonDelay;
@@ skipping 24 matching lines @@
 double ScrollbarThemeMacCommon::initialAutoscrollTimerDelay()
 {
     return gInitialButtonDelay;
 }
 
 double ScrollbarThemeMacCommon::autoscrollTimerDelay()
 {
     return gAutoscrollButtonDelay;
 }
 
-bool ScrollbarThemeMacCommon::shouldDragDocumentInsteadOfThumb(const ScrollbarThemeClient*, const PlatformMouseEvent& event)
+bool ScrollbarThemeMacCommon::shouldDragDocumentInsteadOfThumb(const ScrollbarThemeClient&, const PlatformMouseEvent& event)
 {
     return event.altKey();
 }
 
 int ScrollbarThemeMacCommon::scrollbarPartToHIPressedState(ScrollbarPart part)
 {
     switch (part) {
         case BackButtonStartPart:
             return kThemeTopOutsideArrowPressed;
         case BackButtonEndPart:
@@ skipping 20 matching lines @@
 // static
 bool ScrollbarThemeMacCommon::isOverlayAPIAvailable()
 {
     static bool apiAvailable =
         [NSClassFromString(@"NSScrollerImp") respondsToSelector:@selector(scrollerImpWithStyle:controlSize:horizontal:replacingScrollerImp:)]
         && [NSClassFromString(@"NSScrollerImpPair") instancesRespondToSelector:@selector(scrollerStyle)];
     return apiAvailable;
 }
 
 } // namespace blink