Mac: Don't repaint scrollbars every frame

third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp

Index: third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp
diff --git a/third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp b/third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp
index 13487d835d657377cc8cd2af7d229436487fdd1a..ac80728789b86a04cf08729f922f21849d81794a 100644
--- a/third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp
+++ b/third_party/WebKit/Source/platform/scroll/ScrollableAreaTest.cpp
@@ -5,6 +5,8 @@
 #include "config.h"
 #include "platform/scroll/ScrollableArea.h"
 
+#include "platform/scroll/ScrollbarTheme.h"
+#include "platform/scroll/ScrollbarThemeMock.h"
 #include "platform/testing/TestingPlatformSupport.h"
 #include "public/platform/Platform.h"
 #include "public/platform/WebScheduler.h"
@@ -127,4 +129,36 @@ TEST_F(ScrollableAreaTest, ScrollAnimatorCurrentPositionShouldBeSync)
     EXPECT_EQ(100.0, scrollableArea->scrollAnimator()->currentPosition().y());
 }
 
+TEST_F(ScrollableAreaTest, ScrollbarTrackAndThumbRepaint)

[chrishtr, 2015/11/24 21:15:12]

This doesn't test the mac code...

[ccameron, 2015/11/25 00:23:02]

You're referring to ScrollAnimatorMac? I put quite some time into looking at
what would be required to test the behavior for that. And, I don't think that
exercise should block this patch.

The APIs that ScrollAnimatorMac uses are undocumented and have different
behavior on different OSes (which complicates writing tests that aren't total
flakes). This is probably part of the reason that it has zero existing tests for
its behaviors (and in fact many tests explicitly avoid touching
ScrollAnimatorMac, see [1]).

ScrollAnimatorMac deserves some attention and cleanup (for starters it needs to
change how it animates -- it just fires a timer at 60 Hz -- that shouldn't be
done), and probably a rewrite. But that's an independent issue to this patch.

[1]
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...

+{
+    ScrollbarTheme::setMockScrollbarsEnabled(true);
+    ScrollbarThemeMock::setShouldRepaintAllPartsOnInvalidation(true);
+
+    OwnPtrWillBeRawPtr<MockScrollableArea> scrollableArea = MockScrollableArea::create(IntPoint(0, 100));
+    RefPtrWillBeRawPtr<Scrollbar> scrollbar = Scrollbar::create(scrollableArea.get(), HorizontalScrollbar, RegularScrollbar);
+
+    EXPECT_TRUE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_TRUE(scrollbar->thumbNeedsRepaint());
+    scrollbar->setNeedsPaintInvalidation();
+    EXPECT_TRUE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_TRUE(scrollbar->thumbNeedsRepaint());
+
+    scrollbar->setTrackBackgroundNeedsRepaint(false);
+    scrollbar->setThumbNeedsRepaint(false);
+    EXPECT_FALSE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_FALSE(scrollbar->thumbNeedsRepaint());
+    scrollbar->setNeedsPaintInvalidation();
+    EXPECT_TRUE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_TRUE(scrollbar->thumbNeedsRepaint());
+
+    ScrollbarThemeMock::setShouldRepaintAllPartsOnInvalidation(false);
+    scrollbar->setTrackBackgroundNeedsRepaint(false);
+    scrollbar->setThumbNeedsRepaint(false);
+    EXPECT_FALSE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_FALSE(scrollbar->thumbNeedsRepaint());
+    scrollbar->setNeedsPaintInvalidation();
+    EXPECT_FALSE(scrollbar->trackBackgroundNeedsRepaint());
+    EXPECT_FALSE(scrollbar->thumbNeedsRepaint());
+}
+
 } // namespace blink