[Mac] Respect natural/inverted scroll direction on Lion when gesturing.

chrome/browser/ui/cocoa/browser_window_controller.mm

 // Copyright (c) 2011 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.
 
 #import "chrome/browser/ui/cocoa/browser_window_controller.h"
 
 #include <Carbon/Carbon.h>
 #include <numeric>
 
 #include "base/command_line.h"
@@ skipping 1655 matching lines @@
   // The button shouldn't do anything in incognito.
   [avatarButton_ setOpenMenuOnClick:!browser_->profile()->IsOffTheRecord()];
 
   // Install the view.
   [[[[self window] contentView] superview] addSubview:avatarButton_];
 }
 
 // Documented in 10.6+, but present starting in 10.5. Called when we get a
 // three-finger swipe.
 - (void)swipeWithEvent:(NSEvent*)event {
+  CGFloat deltaX = [event deltaX];
+  CGFloat deltaY = [event deltaY];
+
+  // On Lion, the user can choose to use a "natural" scroll direction with
+  // inverted axes.
+  if ([self isScrollDirectionInverted]) {
+    deltaX *= -1;
+    deltaY *= -1;
+  }
+
   // Map forwards and backwards to history; left is positive, right is negative.
   unsigned int command = 0;
-  if ([event deltaX] > 0.5) {
+  if (deltaX > 0.5) {
     command = IDC_BACK;
-  } else if ([event deltaX] < -0.5) {
+  } else if (deltaX < -0.5) {
     command = IDC_FORWARD;
-  } else if ([event deltaY] > 0.5) {
+  } else if (deltaY > 0.5) {
     // TODO(pinkerton): figure out page-up, http://crbug.com/16305
   } else if ([event deltaY] < -0.5) {
     // TODO(pinkerton): figure out page-down, http://crbug.com/16305
     browser_->ExecuteCommand(IDC_TABPOSE);
   }
 
   // Ensure the command is valid first (ExecuteCommand() won't do that) and
   // then make it so.
   if (browser_->command_updater()->IsCommandEnabled(command))
     browser_->ExecuteCommandWithDisposition(command,
@@ skipping 87 matching lines @@
     // The |normalizedPosition| is scaled from (0,1).
     magnitudes.push_back(touch.normalizedPosition.x -
         beginTouch.normalizedPosition.x);
   }
 
   // Need at least two points to gesture.
   if (magnitudes.size() < 2)
     return;
 
   CGFloat sum = std::accumulate(magnitudes.begin(), magnitudes.end(), 0.0f);
+  // On Lion, the user can choose to use a "natural" scroll direction with
+  // inverted axes.
+  if ([self isScrollDirectionInverted])
+    sum *= -1;
+
   int command_id = 0;
   if (sum > 0.3)
     command_id = IDC_FORWARD;
   else if (sum < -0.3)
     command_id = IDC_BACK;
   else
     return;
 
   if (browser_->command_updater()->IsCommandEnabled(command_id)) {
     browser_->ExecuteCommandWithDisposition(command_id,
@@ skipping 483 matching lines @@
 
 - (BOOL)supportsBookmarkBar {
   return [self supportsWindowFeature:Browser::FEATURE_BOOKMARKBAR];
 }
 
 - (BOOL)isTabbedWindow {
   return browser_->is_type_tabbed();
 }
 
 @end  // @implementation BrowserWindowController(WindowType)