chrome/browser/tabs/tab_strip_model_observer.h

// Copyright (c) 2011 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 CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
#define CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_
#pragma once

class TabContentsWrapper;
class TabStripModel;

////////////////////////////////////////////////////////////////////////////////
//
// TabStripModelObserver
//
//  Objects implement this interface when they wish to be notified of changes
//  to the TabStripModel.
//
//  Two major implementers are the TabStrip, which uses notifications sent
//  via this interface to update the presentation of the strip, and the Browser
//  object, which updates bookkeeping and shows/hides individual TabContentses.
//
//  Register your TabStripModelObserver with the TabStripModel using its
//  Add/RemoveObserver methods.
//
////////////////////////////////////////////////////////////////////////////////
class TabStripModelObserver {
 public:
  // Enumeration of the possible values supplied to TabChangedAt.
  enum TabChangeType {
    // Only the loading state changed.
    LOADING_ONLY,

    // Only the title changed and page isn't loading.
    TITLE_NOT_LOADING,

    // Change not characterized by LOADING_ONLY or TITLE_NOT_LOADING.
    ALL
  };

  // A new TabContents was inserted into the TabStripModel at the specified
  // index. |foreground| is whether or not it was opened in the foreground
  // (selected).
  virtual void TabInsertedAt(TabContentsWrapper* contents,
                             int index,
                             bool foreground);

  // The specified TabContents at |index| is being closed (and eventually
  // destroyed). |tab_strip_model| is the TabStripModel the tab was part of.
  virtual void TabClosingAt(TabStripModel* tab_strip_model,
                            TabContentsWrapper* contents,
                            int index);

  // The specified TabContents at |index| is being detached, perhaps to be
  // inserted in another TabStripModel. The implementer should take whatever
  // action is necessary to deal with the TabContents no longer being present.
  virtual void TabDetachedAt(TabContentsWrapper* contents, int index);

  // The selected TabContents is about to change from |old_contents|.
  // This gives observers a chance to prepare for an impending switch before it
  // happens.
  virtual void TabDeselected(TabContentsWrapper* contents);

  // Sent when the selection changes. The previously selected tab is identified
  // by |old_contents| and the newly selected tab by |new_contents|. |index| is
  // the index of |new_contents|. When using multiple selection this may be sent
  // even when the active tab has not changed. For example, if the selection is
  // extended this method is invoked to inform observers the selection has
  // changed, but |old_contents| and |new_contents| are the same.  If you only
  // care about when the active tab changes, check for when |old_contents|
  // differs from |new_contents|. |user_gesture| specifies whether or not this
  // was done by a user input event (e.g. clicking on a tab, keystroke) or as a
  // side-effect of some other function.
  //
  // TODO(sky): consider not overloading this. Instead rename this to
  // TabActivatedAt (or something) and have TabSelectionChanged as well.
  // TabSelectedAt. This requires renaming everyone to use new terms instead of
  // selection.
  virtual void TabSelectedAt(TabContentsWrapper* old_contents,
                             TabContentsWrapper* new_contents,
                             int index,
                             bool user_gesture);

  // The specified TabContents at |from_index| was moved to |to_index|.
  virtual void TabMoved(TabContentsWrapper* contents,
                        int from_index,
                        int to_index);

  // The specified TabContents at |index| changed in some way. |contents| may
  // be an entirely different object and the old value is no longer available
  // by the time this message is delivered.
  //
  // See TabChangeType for a description of |change_type|.
  virtual void TabChangedAt(TabContentsWrapper* contents,
                            int index,
                            TabChangeType change_type);

  // The tab contents was replaced at the specified index. This is invoked when
  // instant is enabled and the user navigates by way of instant.
  virtual void TabReplacedAt(TabStripModel* tab_strip_model,
                             TabContentsWrapper* old_contents,
                             TabContentsWrapper* new_contents,
                             int index);

  // Invoked when the pinned state of a tab changes. See note in
  // TabMiniStateChanged as to how this relates to TabMiniStateChanged.
  virtual void TabPinnedStateChanged(TabContentsWrapper* contents, int index);

  // Invoked if the mini state of a tab changes.
  // NOTE: this is sent when the pinned state of a non-app tab changes and is
  // sent in addition to TabPinnedStateChanged. UI code typically need not care
  // about TabPinnedStateChanged, but instead this.
  virtual void TabMiniStateChanged(TabContentsWrapper* contents, int index);

  // Invoked when the blocked state of a tab changes.
  // NOTE: This is invoked when a tab becomes blocked/unblocked by a tab modal
  // window.
  virtual void TabBlockedStateChanged(TabContentsWrapper* contents, int index);

  // The TabStripModel now no longer has any tabs. The implementer may
  // use this as a trigger to try and close the window containing the
  // TabStripModel, for example...
  virtual void TabStripEmpty();

  // Sent when the tabstrip model is about to be deleted and any reference held
  // must be dropped.
  virtual void TabStripModelDeleted();

 protected:
  virtual ~TabStripModelObserver() {}
};

#endif  // CHROME_BROWSER_TABS_TAB_STRIP_MODEL_OBSERVER_H_