[Mac] Factor out keyboard shortcut handling from ChromeEventProcessingWindow.

ui/base/cocoa/command_dispatcher.h

+// Copyright 2015 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.
+
+#ifndef UI_BASE_COCOA_COMMAND_DISPATCHER_H_
+#define UI_BASE_COCOA_COMMAND_DISPATCHER_H_
+
+#import <Cocoa/Cocoa.h>
+
+#import "base/mac/scoped_nsobject.h"
+
+@protocol CommandDispatcherDelegate;
+@protocol CommandDispatchingWindow;
+
+// CommandDispatcher guides the processing of key events to ensure key commands
+// are executed in the appropriate order. In particular, it allows a first
+// responder implementing CommandDispatcherTarget to handle an event
+// asynchronously and return unhandled events via -redispatchKeyEvent. An
+// NSWindow can use CommandDispatcher by implementing CommandDispatchingWindow
+// and overriding -[NSWindow -performKeyEquivalent:] and -[NSWindow -sendEvent:]
+// to call the respective CommandDispatcher methods.
+@interface CommandDispatcher : NSObject {
+ @private
+  BOOL redispatchingEvent_;
+  BOOL eventHandled_;
+  NSWindow<CommandDispatchingWindow>* owner_;  // Weak, owns us.
+}
+
+@property(retain, nonatomic) id<CommandDispatcherDelegate> delegate;
+
+- (id)initWithOwner:(NSWindow<CommandDispatchingWindow>*)owner;
+
+// The main entry point for key events. The CommandDispatchingWindow should
+// override -[NSResponder performKeyEquivalent:] and call this instead. Returns
+// YES if the event is handled.
+- (BOOL)performKeyEquivalent:(NSEvent*)event;
+
+// Sends a key event to -[NSApp sendEvent:], but also ensures it is not short-
+// circuited to the CommandDispatcherTarget. This is used to allow default
+// AppKit handling of an event that comes back from CommandDispatcherTarget,
+// e.g. key equivalents in the menu, or window manager commands like Cmd+`. The
+// event must be of type |NSKeyDown|, |NSKeyUp|, or |NSFlagsChanged|. Returns
+// YES if the event is handled.
+- (BOOL)redispatchKeyEvent:(NSEvent*)event;
+
+// The CommandDispatchingWindow should call this before a native -sendEvent.
+// Ensures that a redispatched event is not reposted infinitely. Returns YES if
+// the event is handled.
+- (BOOL)preSendEvent:(NSEvent*)event;
+
+@end
+
+// If the NSWindow's firstResponder implements CommandDispatcherTarget, it is
+// given the first opportunity to process a command. To handle an event

[tapted, 2015/08/26 06:46:54]

nit: Move from "To handle an event..." onto a comment on performKeyEquivalent,
and add some vertical whitespace

[jackhou1, 2015/08/26 07:38:17]

Done.

+// asynchronously, return YES. If the event is ultimately not handled, return
+// the event to the CommandDispatchingWindow via -[[event window]
+// redispatchKeyEvent:event].
+@protocol CommandDispatcherTarget
+- (BOOL)performKeyEquivalent:(NSEvent*)event;
+@end
+
+// Provides CommandDispatcher with the means to redirect key equivalents at
+// different stages of event handling.
+@protocol CommandDispatcherDelegate<NSObject>
+
+// Called before any other event handling, and possibly again if an unhandled
+// event comes back from CommandDispatcherTarget.
+- (BOOL)handledByExtensionCommand:(NSEvent*)event
+                     isRedispatch:(BOOL)isRedispatch;
+
+// Called before the default -performKeyEquivalent, but after the
+// CommandDispatcherTarget has had a chance to intercept it.
+- (BOOL)prePerformKeyEquivalent:(NSEvent*)event window:(NSWindow*)window;
+
+// Called after the default -performKeyEquivalent.
+- (BOOL)postPerformKeyEquivalent:(NSEvent*)event window:(NSWindow*)window;
+
+@end
+
+// The set of methods an NSWindow subclass needs to implement to use
+// CommandDispatcher.
+@protocol CommandDispatchingWindow
+
+// This can be implemented with -[CommandDispatcher -redispatchKeyEvent:]. It's
+// so that callers can simply return events to the NSWindow.
+- (BOOL)redispatchKeyEvent:(NSEvent*)event;
+
+// Short-circuit to the default -[NSResponder performKeyEquivalent:] which
+// CommandDispatcher calls as part of its -performKeyEquivalent flow.
+- (BOOL)defaultPerformKeyEquivalent:(NSEvent*)event;
+
+@end
+
+#endif  // UI_BASE_COCOA_COMMAND_DISPATCHER_H_