refactoring mouse lock to support pepper and WebKit

content/renderer/mouse_lock_dispatcher.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 "content/renderer/mouse_lock_dispatcher.h"
+
+#include "content/common/view_messages.h"
+#include "content/renderer/render_view_impl.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebInputEvent.h"
+#include "third_party/WebKit/Source/WebKit/chromium/public/WebWidget.h"
+
+MouseLockDispatcher::MouseLockDispatcher(RenderViewImpl* render_view_impl)
+    : content::RenderViewObserver(render_view_impl),
+      render_view_impl_(render_view_impl),
+      mouse_locked_(false),
+      pending_lock_request_(false),
+      pending_unlock_request_(false),
+      mouse_lock_webwidget_owner_(NULL),
+      mouse_lock_plugin_owner_(NULL) {
+}
+
+MouseLockDispatcher::~MouseLockDispatcher() {
+}
+
+bool MouseLockDispatcher::LockMouse(WebKit::WebWidget* webwidget,
+                                    webkit::ppapi::PluginInstance* plugin) {
+  DCHECK(!(webwidget && plugin)); // Only one mouse lock target at a time.

[piman, 2012/01/18 19:00:59]

Is it valid to lock with no owner at all?

[scheib, 2012/01/24 01:51:42]

Refactoring has removed this issue, there is only one target now.

+
+  if (MouseLockedOrPendingAction())
+    return false;
+
+  pending_lock_request_ = true;
+  DCHECK(!mouse_lock_webwidget_owner_ && !mouse_lock_plugin_owner_);
+  mouse_lock_webwidget_owner_ = webwidget;
+  mouse_lock_plugin_owner_ = plugin;
+
+  Send(new ViewHostMsg_LockMouse(routing_id()));
+  return true;
+}
+
+void MouseLockDispatcher::UnlockMouse(WebKit::WebWidget* webwidget,
+                                      webkit::ppapi::PluginInstance* plugin) {

[piman, 2012/01/18 19:00:59]

This gets called when the plugin instance gets deleted. From my reading of the
logic, we're still hanging on to the PluginInstance pointer so that we can send
a callback when the unlock actually happened. But at that point the pointer will
be stale.

[scheib, 2012/01/24 01:51:42]

Addressed by creating a new method UnlockMouseAndClearPointer(). Also, verified
the old error by upgrading the mouse_lock sample and that the new code works.

+  if (!MouseLockedOrPendingAction() || pending_unlock_request_)
+    return;
+
+  // Ignore unless the unlock request is for the current lock holder.
+  if (webwidget == mouse_lock_webwidget_owner_ ||
+      plugin == mouse_lock_plugin_owner_) {

[piman, 2012/01/18 19:00:59]

This test should be stricter. E.g. if I do LockMouse(NULL, plugin_instance1);
UnlockMouse(NULL, plugin_instance2); then mouse_lock_webwidget_owner_==NULL, and
webwidget==NULL here, so it will succeed.

[scheib, 2012/01/24 01:51:42]

Done.

+    pending_unlock_request_ = true;
+    Send(new ViewHostMsg_UnlockMouse(routing_id()));
+  }
+}
+
+bool MouseLockDispatcher::IsPointerLockedTo(WebKit::WebWidget* webwidget) {
+  return mouse_locked_ && mouse_lock_webwidget_owner_ == webwidget;
+}
+
+bool MouseLockDispatcher::IsMouseLockedTo(
+    webkit::ppapi::PluginInstance* plugin) {
+  return mouse_locked_ && mouse_lock_plugin_owner_ == plugin;
+}
+
+bool MouseLockDispatcher::WillHandleMouseEvent(
+    const WebKit::WebMouseEvent& event) {
+  if (mouse_locked_ && mouse_lock_plugin_owner_) {
+    DCHECK(!mouse_lock_webwidget_owner_);
+    mouse_lock_plugin_owner_->HandleMouseLockedInputEvent(event);
+
+    // mouse_lock_webwidget_owner_ handles mouse lock in handleInputEvent().
+
+    // If the mouse is locked, only the current owner of the mouse lock can
+    // process mouse events.
+    return true;
+  }
+  return false;
+}
+
+bool MouseLockDispatcher::OnMessageReceived(const IPC::Message& message) {
+  bool handled = true;
+  IPC_BEGIN_MESSAGE_MAP(MouseLockDispatcher, message)
+    IPC_MESSAGE_HANDLER(ViewMsg_LockMouse_ACK, OnLockMouseACK)
+    IPC_MESSAGE_HANDLER(ViewMsg_MouseLockLost, OnMouseLockLost)
+    IPC_MESSAGE_UNHANDLED(handled = false)
+  IPC_END_MESSAGE_MAP()
+  return handled;
+}
+
+void MouseLockDispatcher::OnLockMouseACK(bool succeeded) {
+  // Mouse Lock removes the system cursor and provides all mouse motion as
+  // .movementX/Y values on events all sent to a fixed target. This requires
+  // content to specifically request the mode to be entered.
+  // Mouse Capture is implicitly given for the duration of a drag event, and
+  // sends all mouse events to the initial target of the drag.
+  // If Lock is entered it supercedes any in progress Capture.
+  if (succeeded && render_view_impl_->webwidget())
+      render_view_impl_->webwidget()->mouseCaptureLost();

[piman, 2012/01/18 19:00:59]

could this callback re-enter and cause, say, the content to try to release the
lock? Are we doing the right thing in that case?

[scheib, 2012/01/24 01:51:42]

Moved to after all state changes to prevent reentrant issues.

+
+  DCHECK(!mouse_locked_ && pending_lock_request_);
+
+  mouse_locked_ = succeeded;
+  pending_lock_request_ = false;
+  if (pending_unlock_request_ && !succeeded) {
+    // We have sent an unlock request after the lock request. However, since
+    // the lock request has failed, the unlock request will be ignored by the
+    // browser side and there won't be any response to it.
+    pending_unlock_request_ = false;
+  }
+
+  if (mouse_lock_webwidget_owner_ || mouse_lock_plugin_owner_) {

[piman, 2012/01/18 19:00:59]

(similar question as above) can this be false?

[scheib, 2012/01/24 01:51:42]

Now with UnlockAndClearPointer it is possible for no owner to be on record when
a response comes in. However, I've removed the if() bracket because the code is
safe to false/null owners regardless. 

+    WebKit::WebWidget* last_webwidget_owner = mouse_lock_webwidget_owner_;
+    webkit::ppapi::PluginInstance* last_plugin_owner =
+        mouse_lock_plugin_owner_;
+
+    if (!succeeded) {
+      // Reset mouse lock owner to NULL before calling OnLockMouseACK(), so
+      // that if OnLockMouseACK() results in calls to any mouse lock method
+      // (e.g., LockMouse()), the method will see consistent internal state.
+      mouse_lock_webwidget_owner_ = NULL;
+      mouse_lock_plugin_owner_ = NULL;
+    }
+
+    DCHECK(!mouse_lock_webwidget_owner_ || !mouse_lock_plugin_owner_);
+    if (last_webwidget_owner) {
+      // TODO(scheib): Enable after WebKit pointer lock API has landed.
+      //
+      // if (succeeded)
+      //   last_webwidget_owner->didCompletePointerLock();
+      // else
+      //   last_webwidget_owner->didNotCompletePointerLock();
+    }
+    if (last_plugin_owner)
+      last_plugin_owner->OnLockMouseACK(succeeded);
+  }
+}
+
+void MouseLockDispatcher::OnMouseLockLost() {
+  DCHECK(mouse_locked_ && !pending_lock_request_);
+
+  mouse_locked_ = false;
+  pending_unlock_request_ = false;
+  if (mouse_lock_webwidget_owner_ || mouse_lock_plugin_owner_) {
+    // TODO(scheib): Enable after WebKit pointer lock API has landed.
+    //
+    // WebKit::WebWidget* last_webwidget_owner = mouse_lock_webwidget_owner_;
+    webkit::ppapi::PluginInstance* last_plugin_owner =
+        mouse_lock_plugin_owner_;
+
+    // Reset mouse lock owner to NULL before calling
+    // didLosePointerLock/OnMouseLockLost(), so
+    // that a reentrant call (e.g. to, LockMouse()) will see consistent
+    // internal state.
+    mouse_lock_webwidget_owner_ = NULL;
+    mouse_lock_plugin_owner_ = NULL;
+
+    DCHECK(!mouse_lock_webwidget_owner_ || !mouse_lock_plugin_owner_);
+    // TODO(scheib): Enable after WebKit pointer lock API has landed.
+    //
+    // if (last_webwidget_owner)
+    //   last_webwidget_owner->didLosePointerLock();
+    if (last_plugin_owner)
+      last_plugin_owner->OnMouseLockLost();
+  }
+}
+