[Mac][MC] Allow popup notifications to be dismissed with a swipe gesture.

ui/message_center/cocoa/popup_controller.mm

Index: ui/message_center/cocoa/popup_controller.mm
diff --git a/ui/message_center/cocoa/popup_controller.mm b/ui/message_center/cocoa/popup_controller.mm
index f574fc08062d87bb0ea1ba5d4ce5b43e124436c0..05635b7ce66713b4c7c04fe36a023ca819e0edb4 100644
--- a/ui/message_center/cocoa/popup_controller.mm
+++ b/ui/message_center/cocoa/popup_controller.mm
@@ -4,6 +4,9 @@
 
 #import "ui/message_center/cocoa/popup_controller.h"
 
+#include <cmath>
+
+#import "base/mac/foundation_util.h"
 #import "ui/base/cocoa/window_size_constants.h"
 #import "ui/message_center/cocoa/notification_controller.h"
 #include "ui/message_center/message_center.h"
@@ -13,21 +16,117 @@
 enum {
   NSWindowCollectionBehaviorFullScreenAuxiliary = 1 << 8
 };
+
+enum {

[Robert Sesek, 2013/05/22 23:54:29]

This is copied verbatim from RenderWidgetHostViewDelegateMac (or something).
Should we centralize it in base/ like we did with protocols?

[Nico, 2013/05/23 01:02:56]

Probably a good idea. Can be in a follow-up if you want.

+  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)
+- (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  // MAC_OS_X_VERSION_10_7
 
+////////////////////////////////////////////////////////////////////////////////
+
+@interface MCPopupController (Private)
+- (void)notificationSwipeStarted;
+- (void)notificationSwipeMoved:(CGFloat)amount;
+- (void)notificationSwipeEnded:(BOOL)ended complete:(BOOL)isComplete;
+@end
+
+// Window Subclass /////////////////////////////////////////////////////////////
+
+@interface MCPopupWindow : NSWindow {
+  // The cumulative X and Y scrollingDeltas since the -scrollWheel: event began.
+  NSPoint totalScrollDelta_;
+}
+@end
+
+@implementation MCPopupWindow
+
+- (void)scrollWheel:(NSEvent*)event {
+  // Gesture swiping only exists on 10.7+.
+  if (![event respondsToSelector:@selector(phase)])
+    return;
+
+  NSEventPhase phase = [event phase];
+  BOOL shouldTrackSwipe = NO;
+
+  if (phase == NSEventPhaseBegan) {
+    totalScrollDelta_ = NSZeroPoint;
+  } else if (phase == NSEventPhaseChanged) {
+    shouldTrackSwipe = YES;
+    totalScrollDelta_.x += [event scrollingDeltaX];
+    totalScrollDelta_.y += [event scrollingDeltaY];
+  }
+
+  // Only allow horizontal scrolling.
+  if (std::abs(totalScrollDelta_.x) < std::abs(totalScrollDelta_.y))
+    return;
+
+  if (shouldTrackSwipe) {
+    MCPopupController* controller =
+        base::mac::ObjCCastStrict<MCPopupController>([self windowController]);
+
+    auto handler = ^(CGFloat gestureAmount, NSEventPhase phase,
+                     BOOL isComplete, BOOL* stop) {
+        if (phase == NSEventPhaseBegan) {
+          [controller notificationSwipeStarted];
+          return;
+        }
+
+        [controller notificationSwipeMoved:gestureAmount];
+
+        BOOL ended = phase == NSEventPhaseEnded;
+        if (ended || isComplete)
+          [controller notificationSwipeEnded:ended complete:isComplete];
+    };
+    [event trackSwipeEventWithOptions:0
+             dampenAmountThresholdMin:-1
+                                  max:1
+                         usingHandler:handler];
+  }
+}
+
+@end
+
+////////////////////////////////////////////////////////////////////////////////
+
 @implementation MCPopupController
 
 - (id)initWithNotification:(const message_center::Notification*)notification
     messageCenter:(message_center::MessageCenter*)messageCenter {
-  scoped_nsobject<NSWindow> window(
-      [[NSWindow alloc] initWithContentRect:ui::kWindowSizeDeterminedLater
-                                  styleMask:NSBorderlessWindowMask
-                                    backing:NSBackingStoreBuffered
-                                      defer:YES]);
+  scoped_nsobject<MCPopupWindow> window(
+      [[MCPopupWindow alloc] initWithContentRect:ui::kWindowSizeDeterminedLater
+                                       styleMask:NSBorderlessWindowMask
+                                         backing:NSBackingStoreBuffered
+                                           defer:YES]);
   if ((self = [super initWithWindow:window])) {
+    messageCenter_ = messageCenter;
     notificationController_.reset(
         [[MCNotificationController alloc] initWithNotification:notification
-                                                 messageCenter:messageCenter]);
+                                                 messageCenter:messageCenter_]);
     [window setReleasedWhenClosed:NO];
 
     [window setLevel:NSFloatingWindowLevel];
@@ -55,4 +154,28 @@ enum {
   return [notificationController_ notificationID];
 }
 
+// Private /////////////////////////////////////////////////////////////////////
+
+- (void)notificationSwipeStarted {
+  originalFrame_ = [[self window] frame];
+  swipeGestureEnded_ = NO;
+}
+
+- (void)notificationSwipeMoved:(CGFloat)amount {
+  NSWindow* window = [self window];
+
+  [window setAlphaValue:1.0 - std::abs(amount)];

[dewittj, 2013/05/23 16:28:37]

Is the linear reduction of alpha the most natural?  Should we experiment with
different rates of fadeout?

[Robert Sesek, 2013/05/23 16:31:13]

This isn't actually linear. |amount| is done through some elastic graduation
provided by AppKit.

+  NSRect frame = [window frame];
+  CGFloat originalMin = NSMinX(originalFrame_);
+  frame.origin.x = originalMin + (NSMidX(originalFrame_) - originalMin) *
+                   -amount;
+  [window setFrame:frame display:YES];
+}
+
+- (void)notificationSwipeEnded:(BOOL)ended complete:(BOOL)isComplete {
+  swipeGestureEnded_ |= ended;
+  if (swipeGestureEnded_ && isComplete)
+    messageCenter_->RemoveNotification([self notificationID], /*by_user=*/true);

[Nico, 2013/05/23 01:02:56]

If the user cancels a swipe, does appkit animate back to amount of 0
automatically? i.e. do you need to reset the frame to originalFrame_ or does
that just work?

[Robert Sesek, 2013/05/23 13:00:58]

Yup! AppKit will run the animation back for us.

[dewittj, 2013/05/23 16:28:37]

nit: spaces between comment markers and other text (unless this is a common ObjC
way)

[Robert Sesek, 2013/05/23 16:31:13]

When doing this to "name" parameters, I think this is pretty common:

https://code.google.com/p/chromium/codesearch#search/&q==%5C*/&sq=package:chr...

+}
+
 @end