Mac global keybindings

chrome/browser/extensions/global_shortcut_listener_mac.mm

+// Copyright (c) 2013 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/extensions/global_shortcut_listener_mac.h"
+
+#include <ApplicationServices/ApplicationServices.h>
+#import <Cocoa/Cocoa.h>
+#include <IOKit/hidsystem/ev_keymap.h>
+
+#include "base/mac/foundation_util.h"
+#include "chrome/browser/extensions/api/commands/command_service.h"
+#include "content/public/browser/browser_thread.h"
+#include "ui/base/accelerators/accelerator.h"
+#include "ui/events/event.h"
+#import "ui/events/keycodes/keyboard_code_conversion_mac.h"
+
+using content::BrowserThread;
+using extensions::GlobalShortcutListenerMac;
+
+namespace {
+
+// The media keys subtype. No official docs found, but widely known.
+// http://lists.apple.com/archives/cocoa-dev/2007/Aug/msg00499.html
+const int kSystemDefinedEventMediaKeys = 8;
+
+OSStatus HotKeyHandler(
+    EventHandlerCallRef next_handler, EventRef event, void* user_data) {
+  // Extract the hotkey from the event.
+  EventHotKeyID hot_key_id;
+  int result = GetEventParameter(event, kEventParamDirectObject,
+      typeEventHotKeyID, NULL, sizeof(hot_key_id), NULL, &hot_key_id);
+  if (result != noErr)
+    return result;
+
+  GlobalShortcutListenerMac* shortcut_listener =
+      static_cast<GlobalShortcutListenerMac*>(user_data);
+  shortcut_listener->OnKeyEvent(hot_key_id);
+  return noErr;
+}
+
+ui::KeyboardCode MediaKeyCodeToKeyboardCode(int key_code) {
+  switch (key_code) {
+    case NX_KEYTYPE_PLAY:
+      return ui::VKEY_MEDIA_PLAY_PAUSE;
+    case NX_KEYTYPE_PREVIOUS:
+    case NX_KEYTYPE_REWIND:
+      return ui::VKEY_MEDIA_PREV_TRACK;
+    case NX_KEYTYPE_NEXT:
+    case NX_KEYTYPE_FAST:
+      return ui::VKEY_MEDIA_NEXT_TRACK;
+  }
+  return ui::VKEY_UNKNOWN;
+}
+
+static GlobalShortcutListenerMac* g_instance = NULL;
+
+}  // namespace
+
+namespace extensions {
+
+// static
+GlobalShortcutListener* GlobalShortcutListener::GetInstance() {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+  if (g_instance == NULL) {

[Mark Mentovai, 2013/12/10 03:25:21]

Yes, this is what I meant.

But also:

 - the “static” keyword on line 56 doesn’t contribute anything useful, since
you’re already in an unnamed namespace there.
 - since this function is the only thing that uses g_instance, you might as well
move it right into this function, in which case you should keep the “static”,
obviously.

I would advise changing the other-platform implementations if they also have the
single-threaded property and a CHECK to enforce it.

+    g_instance = new GlobalShortcutListenerMac();
+  }
+  return g_instance;
+}
+
+GlobalShortcutListenerMac::GlobalShortcutListenerMac()
+    : is_listening_(false),
+      hot_key_id_(0),
+      event_tap_(NULL),
+      event_tap_source_(NULL) {
+  CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
+}
+
+GlobalShortcutListenerMac::~GlobalShortcutListenerMac() {
+  // By this point, UnregisterAccelerator should have been called for all
+  // keyboard shortcuts.
+  if (is_listening_)
+    StopListening();
+
+  // If media keys are still registered, make sure we stop the tap.
+  if (IsAnyMediaKeyRegistered())
+    StopWatchingMediaKeys();
+}
+
+void GlobalShortcutListenerMac::StartListening() {
+  DCHECK(!is_listening_);  // Don't start twice.
+  DCHECK(!hot_key_ids_.empty());  // Don't start if no hot key registered.
+  DCHECK(!id_hot_keys_.empty());
+  is_listening_ = true;
+
+  // Install an event handler for hot keys.
+  EventHandlerUPP hot_key_function = NewEventHandlerUPP(HotKeyHandler);
+  EventTypeSpec event_type;
+  event_type.eventClass = kEventClassKeyboard;
+  event_type.eventKind = kEventHotKeyPressed;
+  InstallApplicationEventHandler(
+      hot_key_function, 1, &event_type, this, &event_handler_);
+}
+
+void GlobalShortcutListenerMac::StopListening() {
+  DCHECK(is_listening_);  // No point if we are not already listening.
+  DCHECK(hot_key_ids_.empty());  // Make sure the set is clean.
+  DCHECK(id_hot_keys_.empty());
+  is_listening_ = false;
+
+  // Remove the hot key event handler.
+  RemoveEventHandler(event_handler_);
+}
+
+void GlobalShortcutListenerMac::OnKeyEvent(EventHotKeyID hot_key_id) {
+  // Look up the accelerator based on this hot key ID.
+  const ui::Accelerator& accelerator = id_hot_keys_[hot_key_id.id];
+  NotifyKeyPressed(accelerator);
+}
+
+bool GlobalShortcutListenerMac::OnMediaKeyEvent(int media_key_code) {
+  ui::KeyboardCode key_code = MediaKeyCodeToKeyboardCode(media_key_code);
+  // Create an accelerator corresponding to the keyCode.
+  ui::Accelerator accelerator(key_code, 0);
+  // Look for a match with a bound hot_key.
+  if (hot_key_ids_.find(accelerator) != hot_key_ids_.end()) {
+    // If matched, callback to the event handling system.
+    NotifyKeyPressed(accelerator);
+    return true;
+  }
+  return false;
+}
+
+void GlobalShortcutListenerMac::RegisterAccelerator(
+    const ui::Accelerator& accelerator,
+    GlobalShortcutListener::Observer* observer) {
+  if (hot_key_ids_.find(accelerator) != hot_key_ids_.end()) {
+    // The shortcut has already been registered. Some shortcuts, such as
+    // MediaKeys can have multiple targets, all keyed off of the same
+    // accelerator.
+    return;
+  }
+
+  // If this is the first media key registered, start the event tap.
+  if (CommandService::IsMediaKey(accelerator) && !IsAnyMediaKeyRegistered()) {
+    StartWatchingMediaKeys();
+  }
+
+  // Register hot_key if they are non-media keyboard shortcuts.
+  if (!CommandService::IsMediaKey(accelerator))
+    RegisterHotKey(accelerator, hot_key_id_);
+
+  // Store the hotkey-ID mappings we will need for lookup later.
+  id_hot_keys_[hot_key_id_] = accelerator;
+  hot_key_ids_[accelerator] = hot_key_id_;
+  ++hot_key_id_;
+  GlobalShortcutListener::RegisterAccelerator(accelerator, observer);
+}
+
+void GlobalShortcutListenerMac::UnregisterAccelerator(
+    const ui::Accelerator& accelerator,
+    GlobalShortcutListener::Observer* observer) {
+  // Unregister the hot_key if it's a keyboard shortcut.
+  if (!CommandService::IsMediaKey(accelerator))
+    UnregisterHotKey(accelerator);
+
+  // Remove hot_key from the mappings.
+  int id = hot_key_ids_[accelerator];
+  id_hot_keys_.erase(id);
+  hot_key_ids_.erase(accelerator);
+  GlobalShortcutListener::UnregisterAccelerator(accelerator, observer);
+
+  // If we unregistered a media key, and now if no media keys are registered,
+  // stop the media key tap.
+  if (CommandService::IsMediaKey(accelerator) && !IsAnyMediaKeyRegistered()) {
+    StopWatchingMediaKeys();
+  }
+}
+
+void GlobalShortcutListenerMac::RegisterHotKey(
+    const ui::Accelerator& accelerator, int hot_key_id) {
+  EventHotKeyRef hot_key_ref;
+  EventHotKeyID event_hot_key_id;
+
+  // Signature uniquely identifies the application that owns this hot_key.
+  event_hot_key_id.signature = base::mac::CreatorCodeForApplication();
+  event_hot_key_id.id = hot_key_id;
+
+  // Translate ui::Accelerator modifiers to cmdKey, altKey, etc.
+  int modifiers = 0;
+  modifiers |= (accelerator.IsShiftDown() ? shiftKey : 0);
+  modifiers |= (accelerator.IsCtrlDown() ? controlKey : 0);
+  modifiers |= (accelerator.IsAltDown() ? optionKey : 0);
+  modifiers |= (accelerator.IsCmdDown() ? cmdKey : 0);
+
+  unichar character;
+  unichar character_nomods;
+  int key_code = ui::MacKeyCodeForWindowsKeyCode(accelerator.key_code(), 0,
+      &character, &character_nomods);
+
+  // Register the event hot key.
+  RegisterEventHotKey(key_code, modifiers, event_hot_key_id,
+      GetApplicationEventTarget(), 0, &hot_key_ref);
+
+  id_hot_key_refs_[hot_key_id] = hot_key_ref;
+}
+
+void GlobalShortcutListenerMac::UnregisterHotKey(
+    const ui::Accelerator& accelerator) {
+  // Get the ref corresponding to this accelerator.
+  int id = hot_key_ids_[accelerator];
+  EventHotKeyRef ref = id_hot_key_refs_[id];
+  // Unregister the event hot key.
+  UnregisterEventHotKey(ref);
+
+  // Remove the event from the mapping.
+  id_hot_key_refs_.erase(id);
+}
+
+void GlobalShortcutListenerMac::StartWatchingMediaKeys() {
+  // Make sure there's no existing event tap.
+  DCHECK(event_tap_ == NULL);
+
+  // Add an event tap to intercept the system defined media key events.
+  event_tap_ = CGEventTapCreate(kCGSessionEventTap,
+      kCGHeadInsertEventTap,
+      kCGEventTapOptionDefault,
+      CGEventMaskBit(NX_SYSDEFINED),
+      EventTapCallback,
+      this);
+  if (event_tap_ == NULL) {
+    LOG(ERROR) << "Error: failed to create event tap.";
+    return;
+  }
+
+  event_tap_source_ = CFMachPortCreateRunLoopSource(kCFAllocatorSystemDefault,
+      event_tap_, 0);
+  if (event_tap_source_ == NULL) {
+    LOG(ERROR) << "Error: failed to create new run loop source.";
+    return;
+  }
+
+  CFRunLoopAddSource(CFRunLoopGetCurrent(), event_tap_source_,
+      kCFRunLoopCommonModes);
+}
+
+void GlobalShortcutListenerMac::StopWatchingMediaKeys() {
+  CFRunLoopRemoveSource(CFRunLoopGetCurrent(), event_tap_source_,
+      kCFRunLoopCommonModes);
+
+  // Invalidate the event tap.
+  DCHECK(event_tap_ != NULL);
+  CFMachPortInvalidate(event_tap_);
+  CFRelease(event_tap_);
+  event_tap_ = NULL;
+
+  // Release the event tap source.
+  DCHECK(event_tap_source_ != NULL);
+  CFRelease(event_tap_source_);
+  event_tap_source_ = NULL;
+}
+
+bool GlobalShortcutListenerMac::IsAnyMediaKeyRegistered() {
+  // Iterate through registered accelerators, looking for media keys.
+  HotKeyIdMap::iterator iter;
+  for (iter = hot_key_ids_.begin(); iter != hot_key_ids_.end(); ++iter) {
+    if (CommandService::IsMediaKey(iter->first))
+      return true;
+  }
+  return false;
+}
+
+// Processed events should propagate if they aren't handled by any listeners.
+// For events that don't matter, this handler should return as quickly as
+// possible.
+// Returning event causes the event to propagate to other applications.
+// Returning NULL prevents the event from propagating.
+// static
+CGEventRef GlobalShortcutListenerMac::EventTapCallback(
+    CGEventTapProxy proxy, CGEventType type, CGEventRef event, void* refcon) {
+  GlobalShortcutListenerMac* shortcut_listener =
+      static_cast<GlobalShortcutListenerMac*>(refcon);
+
+  // Handle the timeout case by re-enabling the tap.
+  if (type == kCGEventTapDisabledByTimeout) {
+    CGEventTapEnable(shortcut_listener->event_tap_, TRUE);
+    return event;
+  }
+
+  // Convert the CGEvent to an NSEvent for access to the data1 field.
+  NSEvent* ns_event = [NSEvent eventWithCGEvent:event];
+  if (ns_event == nil) {
+    return event;
+  }
+
+  // Ignore events that are not system defined media keys.
+  if (type != NX_SYSDEFINED ||
+      [ns_event type] != NSSystemDefined ||
+      [ns_event subtype] != kSystemDefinedEventMediaKeys) {
+    return event;
+  }
+
+  NSInteger data1 = [ns_event data1];
+  // Ignore media keys that aren't previous, next and play/pause.
+  // Magical constants are from http://weblog.rogueamoeba.com/2007/09/29/
+  int key_code = ((data1 & 0xFFFF0000) >> 16);
+  if (key_code != NX_KEYTYPE_PLAY && key_code != NX_KEYTYPE_NEXT &&
+      key_code != NX_KEYTYPE_PREVIOUS && key_code != NX_KEYTYPE_FAST &&
+      key_code != NX_KEYTYPE_REWIND) {
+    return event;
+  }
+
+  int key_flags = (data1 & 0x0000FFFF);
+  bool is_key_pressed = (((key_flags & 0xFF00) >> 8)) == 0xA;
+
+  // If the key wasn't pressed (eg. was released), ignore this event.
+  if (!is_key_pressed)
+    return event;
+
+  // Now we have a media key that we care about. Send it to the caller.
+  bool was_handled = shortcut_listener->OnMediaKeyEvent(key_code);
+
+  // Prevent event from proagating to other apps if handled by Chrome.
+  if (was_handled)
+    return NULL;
+
+  // By default, pass the event through.
+  return event;
+}
+
+}  // namespace extensions