mac: Only let two-finger-scrolling trigger history if web doesn't swallow gesture

chrome/browser/renderer_host/render_widget_host_view_mac.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.
 
+#include "chrome/browser/renderer_host/render_widget_host_view_mac.h"
+
 #include <QuartzCore/QuartzCore.h>
 
-#include "chrome/browser/renderer_host/render_widget_host_view_mac.h"
+#include <cmath>
 
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
 #include "base/mac/mac_util.h"
 #include "base/mac/scoped_cftyperef.h"
 #import "base/mac/scoped_nsautorelease_pool.h"
 #include "base/metrics/histogram.h"
 #import "base/memory/scoped_nsobject.h"
 #include "base/string_util.h"
 #include "base/sys_info.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/browser_trial.h"
+#include "chrome/browser/mac/closure_blocks_leopard_compat.h"
 #import "chrome/browser/renderer_host/accelerated_plugin_view_mac.h"
 #import "chrome/browser/renderer_host/text_input_client_mac.h"
 #include "chrome/browser/spellchecker/spellchecker_platform_engine.h"
+#include "chrome/browser/ui/browser.h"
+#include "chrome/browser/ui/browser_list.h"
 #import "chrome/browser/ui/cocoa/rwhvm_editcommand_helper.h"
 #import "chrome/browser/ui/cocoa/view_id_util.h"
 #include "chrome/common/render_messages.h"
 #include "chrome/common/spellcheck_messages.h"
 #import "content/browser/accessibility/browser_accessibility_cocoa.h"
 #include "content/browser/browser_thread.h"
 #include "content/browser/gpu/gpu_process_host.h"
 #include "content/browser/gpu/gpu_process_host_ui_shim.h"
 #include "content/browser/plugin_process_host.h"
 #include "content/browser/renderer_host/backing_store_mac.h"
@@ skipping 16 matching lines @@
 #include "ui/gfx/surface/io_surface_support_mac.h"
 #include "webkit/glue/webaccessibility.h"
 #include "webkit/plugins/npapi/webplugin.h"
 
 using WebKit::WebInputEvent;
 using WebKit::WebInputEventFactory;
 using WebKit::WebMouseEvent;
 using WebKit::WebMouseWheelEvent;
 using WebKit::WebGestureEvent;
 
+// Forward-declare symbols that are part of the 10.7 SDK.

[Mark Mentovai, 2011/08/15 16:55:36]

These are just declarations. Not too much about them is specifically “forward.”

(Did you swipe the comment from somewhere? I just mentioned the same nit on a
recent Avi change.)

[Nico, 2011/08/15 17:05:30]

Removed "Forward-".
Yes, that was from browser_window_controller.mm where I deleted the comment.

+#if !defined(MAC_OS_X_VERSION_10_7) || \
+    MAC_OS_X_VERSION_MAX_ALLOWED < MAC_OS_X_VERSION_10_7
+
+enum {
+    NSEventPhaseNone        = 0, // event not associated with a phase.
+    NSEventPhaseBegan       = 0x1 << 0,
+    NSEventPhaseStationary  = 0x1 << 1,
+    NSEventPhaseChanged     = 0x1 << 2,
+    NSEventPhaseEnded       = 0x1 << 3,
+    NSEventPhaseCancelled   = 0x1 << 4,
+};
+typedef NSUInteger NSEventPhase;
+
+enum {
+     NSEventSwipeTrackingLockDirection = 0x1 << 0,
+     NSEventSwipeTrackingClampGestureAmount = 0x1 << 1
+};
+typedef NSUInteger NSEventSwipeTrackingOptions;
+
+
+@interface NSEvent (LionAPI)
++ (BOOL)isSwipeTrackingFromScrollEventsEnabled;
+
+- (NSEventPhase)phase;
+- (CGFloat)scrollingDeltaX;
+- (CGFloat)scrollingDeltaY;
+- (void)trackSwipeEventWithOptions:(NSEventSwipeTrackingOptions)options
+          dampenAmountThresholdMin:(CGFloat)minDampenThreshold
+                               max:(CGFloat)maxDampenThreshold
+                      usingHandler:(void (^)(CGFloat gestureAmount,
+                                             NSEventPhase phase,
+                                             BOOL isComplete,
+                                             BOOL *stop))trackingHandler;
+@end
+
+#endif  // 10.7
+
 static inline int ToWebKitModifiers(NSUInteger flags) {
   int modifiers = 0;
   if (flags & NSControlKeyMask) modifiers |= WebInputEvent::ControlKey;
   if (flags & NSShiftKeyMask) modifiers |= WebInputEvent::ShiftKey;
   if (flags & NSAlternateKeyMask) modifiers |= WebInputEvent::AltKey;
   if (flags & NSCommandKeyMask) modifiers |= WebInputEvent::MetaKey;
   return modifiers;
 }
 
 // Private methods:
@@ skipping 942 matching lines @@
 
 void RenderWidgetHostViewMac::ForceTextureReload() {
   plugin_container_manager_.ForceTextureReload();
 }
 
 void RenderWidgetHostViewMac::SetVisuallyDeemphasized(const SkColor* color,
                                                       bool animate) {
   // This is not used on mac.
 }
 
+void RenderWidgetHostViewMac::UnhandledWheelEvent(
+    const WebKit::WebMouseWheelEvent& event) {
+  [cocoa_view_ setGotUnhandledWheelEvent:YES];
+}
+
+void RenderWidgetHostViewMac::SetHasHorizontalScrollbar(
+    bool has_horizontal_scrollbar) {
+  [cocoa_view_ setHasHorizontalScrollbar:has_horizontal_scrollbar];
+}
+
+void RenderWidgetHostViewMac::SetScrollOffsetPinning(
+    bool is_pinned_to_left, bool is_pinned_to_right) {
+  [cocoa_view_ setPinnedLeft:is_pinned_to_left];
+  [cocoa_view_ setPinnedRight:is_pinned_to_right];
+}
+
 void RenderWidgetHostViewMac::ShutdownHost() {
   shutdown_factory_.RevokeAll();
   render_widget_host_->Shutdown();
   // Do not touch any members at this point, |this| has been deleted.
 }
 
 gfx::Rect RenderWidgetHostViewMac::GetViewCocoaBounds() const {
   return gfx::Rect(NSRectToCGRect([cocoa_view_ bounds]));
 }
 
@@ skipping 63 matching lines @@
       DisablePasswordInput();
   }
 }
 
 // RenderWidgetHostViewCocoa ---------------------------------------------------
 
 @implementation RenderWidgetHostViewCocoa
 
 @synthesize selectedRange = selectedRange_;
 @synthesize markedRange = markedRange_;
+@synthesize gotUnhandledWheelEvent = gotUnhandledWheelEvent_;
+@synthesize isPinnedLeft = isPinnedLeft_;
+@synthesize isPinnedRight = isPinnedRight_;
+@synthesize hasHorizontalScrollbar = hasHorizontalScrollbar_;
 
 - (id)initWithRenderWidgetHostViewMac:(RenderWidgetHostViewMac*)r {
   self = [super initWithFrame:NSZeroRect];
   if (self) {
     editCommand_helper_.reset(new RWHVMEditCommandHelper);
     editCommand_helper_->AddEditingSelectorsToClass([self class]);
 
     renderWidgetHostView_.reset(r);
     canBeKeyView_ = YES;
     focusedPluginIdentifier_ = -1;
@@ skipping 110 matching lines @@
     renderWidgetHostView_->render_widget_host_->ForwardMouseEvent(event);
 }
 
 - (void)beginGestureWithEvent:(NSEvent*)event {
   if (base::mac::IsOSLionOrLater() &&
       [event subtype] == kIOHIDEventTypeScroll &&
       renderWidgetHostView_->render_widget_host_) {
     WebGestureEvent webEvent = WebInputEventFactory::gestureEvent(event, self);
     renderWidgetHostView_->render_widget_host_->ForwardGestureEvent(webEvent);
   }
-
-  // Forward the gesture event to the next responder so that the browser window
-  // controller has a chance to act on back/forward gestures.
-  [[self nextResponder] beginGestureWithEvent:event];

[Mark Mentovai, 2011/08/15 16:55:36]

Nice subtraction. Thanks to Alexei for catching it.

 }
 
 - (void)endGestureWithEvent:(NSEvent*)event {
   if (base::mac::IsOSLionOrLater() &&
       [event subtype] == kIOHIDEventTypeScroll &&
       renderWidgetHostView_->render_widget_host_) {
     WebGestureEvent webEvent = WebInputEventFactory::gestureEvent(event, self);
     renderWidgetHostView_->render_widget_host_->ForwardGestureEvent(webEvent);
   }
-
-  // Forward the gesture event to the next responder so that the browser window
-  // controller has a chance to act on back/forward gestures.
-  [[self nextResponder] endGestureWithEvent:event];
 }
 
 - (BOOL)performKeyEquivalent:(NSEvent*)theEvent {
   // |performKeyEquivalent:| is sent to all views of a window, not only down the
   // responder chain (cf. "Handling Key Equivalents" in
   // http://developer.apple.com/mac/library/documentation/Cocoa/Conceptual/EventOverview/HandlingKeyEvents/HandlingKeyEvents.html
   // ). We only want to handle key equivalents if we're first responder.
   if ([[self window] firstResponder] != self)
     return NO;
 
@@ skipping 229 matching lines @@
       event.skip_in_browser = true;
       widgetHost->ForwardKeyboardEvent(event);
     }
   }
 
   // Possibly autohide the cursor.
   if ([RenderWidgetHostViewCocoa shouldAutohideCursorForEvent:theEvent])
     [NSCursor setHiddenUntilMouseMoves:YES];
 }
 
-- (void)scrollWheel:(NSEvent *)theEvent {
+- (BOOL)maybeHandleHistorySwiping:(NSEvent*)theEvent {

[Mark Mentovai, 2011/08/15 16:55:36]

Since you don’t declare this in an @interface, you should stick a
one-or-two-line comment above it just letting readers know what it does and what
it returns.

[Nico, 2011/08/15 17:05:30]

Done.

+  BOOL canUseLionApis = [theEvent respondsToSelector:@selector(phase)];
+  if (!canUseLionApis)
+    return NO;
+
+  // Scroll events always go to the web first, and can only trigger history
+  // swiping if they come back unhandled.
+  if ([theEvent phase] == NSEventPhaseBegan) {
+    totalScrollDelta_ = NSZeroSize;
+    gotUnhandledWheelEvent_ = false;
+  }
+
+  if (gotUnhandledWheelEvent_ &&
+      [NSEvent isSwipeTrackingFromScrollEventsEnabled] &&
+      [theEvent phase] == NSEventPhaseChanged) {
+    totalScrollDelta_.width += [theEvent scrollingDeltaX];
+    totalScrollDelta_.height += [theEvent scrollingDeltaY];
+
+    bool isHorizontalGesture =
+      std::abs(totalScrollDelta_.width) > std::abs(totalScrollDelta_.height);

[Mark Mentovai, 2011/08/15 16:55:36]

Are the |abs| calls helpful here at all? Can’t we do the inequality in the
floating-point domain? (Drop the <cmath> #include if so.)

[Nico, 2011/08/15 17:05:30]

Yes, width and height can be both positive or negative depending on the
direction of the swipe. We care only about "is this more horizontal than
vertical", not the sign, so abs is what we want. (If I understood the question
correctly.)

[Mark Mentovai, 2011/08/15 17:58:24]

Nico wrote:
My question was bogus anyway. Need more 0xc0ffee.

+
+    bool isRightScroll = [theEvent scrollingDeltaX] < 0;
+    bool goForward = isRightScroll;
+
+    if (isHorizontalGesture &&
+        // If "forward" is inactive and the user rubber-bands to the right,
+        // "isPinnedLeft" will be false.  When the user then rubber-bands to
+        // the left in the same gesture, that should trigger history
+        // immediately if there's no scrollbar, hence the check for
+        // hasHorizontalScrollbar_.
+        (!hasHorizontalScrollbar_ ||
+        // One would think we have to check canGoBack / canGoForward here, but
+        // that's actually done in the renderer
+        // (ChromeClientImpl::shouldRubberBand()), when it decides if it should
+        // rubberband or send back an event unhandled.
+            (isPinnedLeft_ && !isRightScroll) ||
+            (isPinnedRight_ && isRightScroll))) {
+      // The way this api works: gestureAmount is between -1 and 1 (float). If
+      // the user does the gesture for more than about 25% (i.e. < -0.25 or >
+      // 0.25) and then lets go, it is accepted, we get a NSEventPhaseEnded,
+      // and after that the block is called with amounts animating towards 1
+      // (or -1, depending on the direction).  If the user lets go below that
+      // threshold, we get NSEventPhaseCancelled, and the amount animates
+      // toward 0.
+      [theEvent trackSwipeEventWithOptions:0
+                  dampenAmountThresholdMin:-1
+                                       max:1
+                              usingHandler:^(CGFloat gestureAmount,
+                                             NSEventPhase phase,
+                                             BOOL isComplete,
+                                             BOOL *stop) {
+          // |gestureAmount| obeys -[NSEvent isDirectionInvertedFromDevice]
+          // automatically.
+          // TODO(thakis): UI.
+          Browser* browser = BrowserList::GetLastActive();
+          if (phase == NSEventPhaseEnded && browser) {
+            if (goForward)
+              browser->GoForward(CURRENT_TAB);
+            else
+              browser->GoBack(CURRENT_TAB);
+          }
+        }];
+      return YES;
+    }
+  }
+  return NO;
+}
+
+- (void)scrollWheel:(NSEvent*)theEvent {
   [self cancelChildPopups];
 
+  if ([self maybeHandleHistorySwiping:theEvent])
+    return;
+
   const WebMouseWheelEvent& event =
       WebInputEventFactory::mouseWheelEvent(theEvent, self);
   if (renderWidgetHostView_->render_widget_host_)
     renderWidgetHostView_->render_widget_host_->ForwardWheelEvent(event);
 }
 
 // See the comment in RenderWidgetHostViewMac::Destroy() about cancellation
 // events. On the Mac we must kill popups on outside events, thus this lovely
 // case of filicide caused by events on parent views.
 - (void)cancelChildPopups {
@@ skipping 1248 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end