Experimental Extension Keybinding (first cut).

ui/base/accelerators/accelerator_manager.cc

 // Copyright (c) 2012 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 "ui/base/accelerators/accelerator_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 
 namespace ui {
 
 AcceleratorManager::AcceleratorManager() : last_event_type_(ET_KEY_PRESSED) {
 }
 
 AcceleratorManager::~AcceleratorManager() {
 }
 
 void AcceleratorManager::Register(const Accelerator& accelerator,
+                                  HandlerPriority priority,
                                   AcceleratorTarget* target) {
-  AcceleratorTargetList& targets = accelerators_[accelerator];
+  AcceleratorTargetList& targets = accelerators_[accelerator].second;
   DCHECK(std::find(targets.begin(), targets.end(), target) == targets.end())
       << "Registering the same target multiple times";
-  targets.push_front(target);
+
+  // All priority accelerators go to the front of the line.
+  if (priority) {
+    DCHECK(!accelerators_[accelerator].first)
+        << "Only one _priority_ handler can be registered";
+    targets.push_front(target);
+    // Mark that we have a priority accelerator at the front.
+    accelerators_[accelerator].first = true;
+    return;
+  }
+
+  // We are registering a normal priority handler. If no priority accelerator
+  // handler has been registered before us, just add the new handler to the
+  // front. Otherwise, register it after the first (only) priority handler.
+  if (!accelerators_[accelerator].first)
+    targets.push_front(target);
+  else
+    targets.insert(++targets.begin(), target);
 }
 
 void AcceleratorManager::Unregister(const Accelerator& accelerator,
                                     AcceleratorTarget* target) {
   AcceleratorMap::iterator map_iter = accelerators_.find(accelerator);
   if (map_iter == accelerators_.end()) {
     NOTREACHED() << "Unregistering non-existing accelerator";
     return;
   }
 
-  AcceleratorTargetList* targets = &map_iter->second;
+  AcceleratorTargetList* targets = &map_iter->second.second;
   AcceleratorTargetList::iterator target_iter =
       std::find(targets->begin(), targets->end(), target);
   if (target_iter == targets->end()) {
     NOTREACHED() << "Unregistering accelerator for wrong target";
     return;
   }
 
+  // Check to see if we have a priority handler and whether we are removing it.
+  if (accelerators_[accelerator].first && target_iter == targets->begin()) {
+    // We've are taking the priority accelerator away, flip the priority flag.
+    accelerators_[accelerator].first = false;
+  }
+
   targets->erase(target_iter);
 }
 
 void AcceleratorManager::UnregisterAll(AcceleratorTarget* target) {
   for (AcceleratorMap::iterator map_iter = accelerators_.begin();
        map_iter != accelerators_.end(); ++map_iter) {
-    AcceleratorTargetList* targets = &map_iter->second;
+    AcceleratorTargetList* targets = &map_iter->second.second;
     targets->remove(target);
   }
 }
 
 bool AcceleratorManager::Process(const Accelerator& accelerator) {
   bool result = false;
   AcceleratorMap::iterator map_iter = accelerators_.find(accelerator);
   if (map_iter != accelerators_.end() && ShouldHandle(accelerator)) {
     // We have to copy the target list here, because an AcceleratorPressed
     // event handler may modify the list.
-    AcceleratorTargetList targets(map_iter->second);
+    AcceleratorTargetList targets(map_iter->second.second);
     for (AcceleratorTargetList::iterator iter = targets.begin();
          iter != targets.end(); ++iter) {
       if ((*iter)->CanHandleAccelerators() &&
           (*iter)->AcceleratorPressed(accelerator)) {
         result = true;
         break;
       }
     }
   }
   last_event_type_ = accelerator.type();
   return result;
 }
 
 AcceleratorTarget* AcceleratorManager::GetCurrentTarget(
     const Accelerator& accelerator) const {
   AcceleratorMap::const_iterator map_iter = accelerators_.find(accelerator);
-  if (map_iter == accelerators_.end() || map_iter->second.empty())
+  if (map_iter == accelerators_.end() || map_iter->second.second.empty())
     return NULL;
-  return map_iter->second.front();
+  return map_iter->second.second.front();
+}
+
+bool AcceleratorManager::HasPriorityHandler(
+    const Accelerator& accelerator) const {
+  AcceleratorMap::const_iterator map_iter = accelerators_.find(accelerator);
+  if (map_iter == accelerators_.end() || map_iter->second.second.empty())
+    return false;
+
+  // Check if we have a priority handler. If not, there's no more work needed.
+  if (!map_iter->second.first)
+    return false;
+
+  // If the priority handler says it cannot handle the accelerator, we must not
+  // count it as one.
+  return map_iter->second.second.front()->CanHandleAccelerators();
 }
 
 bool AcceleratorManager::ShouldHandle(const Accelerator& accelerator) const {
   if (accelerator.type() != ET_KEY_RELEASED &&
       accelerator.type() != ET_TRANSLATED_KEY_RELEASE) {
     return true;
   }
   // This check is necessary e.g. not to process the Shift+Alt+ET_KEY_RELEASED
   // Accelerator for Chrome OS (see ash/accelerators/accelerator_controller.cc)
   // when Shift+Alt+Tab is pressed and then Tab is released.
   if (last_event_type_ == ET_KEY_PRESSED ||
       last_event_type_ == ET_TRANSLATED_KEY_PRESS) {
     return true;
   }
   return false;
 }
 
 }  // namespace ui