Add scrollBounce option and disable it by default

atom/browser/web_contents_preferences.cc

@@ -141,6 +141,14 @@ void WebContentsPreferences::AppendExtraCommandLineSwitches(
     command_line->AppendSwitchASCII(switches::kOpenerID,
                                     base::IntToString(opener_id));
 
+#if defined(OS_MACOSX)
+  // Enable scroll bounce.
+  bool scroll_bounce;
+  if (web_preferences.GetBoolean(options::kScrollBounce, &scroll_bounce) &&
+      scroll_bounce)
+    command_line->AppendSwitch(switches::kScrollBounce);
+#endif
+
   // Enable blink features.
   std::string blink_features;
   if (web_preferences.GetString(options::kBlinkFeatures, &blink_features))

atom/common/options_switches.cc

@@ -103,6 +103,9 @@ const char kExperimentalCanvasFeatures[] = "experimentalCanvasFeatures";
 // Opener window's ID.
 const char kOpenerID[] = "openerId";
 
+// Enable the rubber banding effect.
+const char kScrollBounce[] = "scrollBounce";
+
 // Enable blink features.
 const char kBlinkFeatures[] = "blinkFeatures";
 
@@ -146,6 +149,7 @@ const char kPreloadURL[]      = "preload-url";
 const char kNodeIntegration[] = "node-integration";
 const char kGuestInstanceID[] = "guest-instance-id";
 const char kOpenerID[]        = "opener-id";
+const char kScrollBounce[]    = "scroll-bounce";
 
 // Widevine options
 // Path to Widevine CDM binaries.

atom/common/options_switches.h

@@ -56,6 +56,7 @@ extern const char kGuestInstanceID[];
 extern const char kExperimentalFeatures[];
 extern const char kExperimentalCanvasFeatures[];
 extern const char kOpenerID[];
+extern const char kScrollBounce[];
 extern const char kBlinkFeatures[];
 
 }   // namespace options
@@ -82,6 +83,7 @@ extern const char kPreloadURL[];
 extern const char kNodeIntegration[];
 extern const char kGuestInstanceID[];
 extern const char kOpenerID[];
+extern const char kScrollBounce[];
 
 extern const char kWidevineCdmPath[];
 extern const char kWidevineCdmVersion[];

atom/renderer/atom_renderer_client.cc

@@ -36,6 +36,11 @@
 #include "third_party/WebKit/public/web/WebRuntimeFeatures.h"
 #include "third_party/WebKit/public/web/WebView.h"
 
+#if defined(OS_MACOSX)
+#include "base/mac/mac_util.h"
+#include "base/strings/sys_string_conversions.h"
+#endif
+
 #if defined(OS_WIN)
 #include <shlobj.h>
 #endif
@@ -97,6 +102,7 @@ void AtomRendererClient::RenderThreadStarted() {
   content::RenderThread::Get()->AddObserver(this);
 
 #if defined(OS_WIN)
+  // Set ApplicationUserModelID in renderer process.
   base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
   base::string16 app_id =
       command_line->GetSwitchValueNative(switches::kAppUserModelId);
@@ -104,6 +110,19 @@ void AtomRendererClient::RenderThreadStarted() {
     SetCurrentProcessExplicitAppUserModelID(app_id.c_str());
   }
 #endif
+
+#if defined(OS_MACOSX)
+  // Disable rubber banding by default.
+  base::CommandLine* command_line = base::CommandLine::ForCurrentProcess();
+  if (!command_line->HasSwitch(switches::kScrollBounce)) {
+    base::ScopedCFTypeRef<CFStringRef> key(
+        base::SysUTF8ToCFStringRef("NSScrollViewRubberbanding"));
+    base::ScopedCFTypeRef<CFStringRef> value(
+        base::SysUTF8ToCFStringRef("false"));
+    CFPreferencesSetAppValue(key, value, kCFPreferencesCurrentApplication);
+    CFPreferencesAppSynchronize(kCFPreferencesCurrentApplication);
+  }
+#endif
 }
 
 void AtomRendererClient::RenderFrameCreated(

docs/api/browser-window.md

@@ -170,6 +170,8 @@ The `webPreferences` option is an object that can have following properties:
   canvas features. Default is `false`.
 * `directWrite` Boolean - Enables DirectWrite font rendering system on
   Windows. Default is `true`.
+* `scrollBounce` Boolean - Enables scroll bounce (rubber banding) effect on
+  OS X. Default is `false`.
 * `blinkFeatures` String - A list of feature strings separated by `,`, like
   `CSSVariables,KeyboardEventKey`. The full list of supported feature strings
   can be found in the [setFeatureEnabledFromString][blink-feature-string]