114 lines
5 KiB
C++
114 lines
5 KiB
C++
/////////////////////////////////////////////////////////////////////////////
|
|
// Name: docs/doxygen/overviews/persistence.h
|
|
// Purpose: overview of persistent objects
|
|
// Author: Vadim Zeitlin
|
|
// Created: 2009-01-23
|
|
// Copyright: (c) 2009 Vadim Zeitlin <vadim@wxwidgets.org>
|
|
// Licence: wxWindows licence
|
|
/////////////////////////////////////////////////////////////////////////////
|
|
|
|
/**
|
|
|
|
@page overview_persistence Persistent Objects Overview
|
|
|
|
@tableofcontents
|
|
|
|
Persistent objects are simply the objects which automatically save their state
|
|
when they are destroyed and restore it when they are recreated, even during
|
|
another program invocation.
|
|
|
|
Most often, persistent objects are, in fact, persistent windows as it is
|
|
especially convenient to automatically restore the UI state when the program is
|
|
restarted but an object of any class can be made persistent. Moreover,
|
|
persistence is implemented in a non-intrusive way so that the original object
|
|
class doesn't need to be modified at all in order to add support for saving and
|
|
restoring its properties.
|
|
|
|
The persistence framework includes the following components:
|
|
|
|
- wxPersistenceManager which all persistent objects register themselves with.
|
|
This class handles actual saving and restoring of persistent data as well as
|
|
various global aspects of persistence, e.g. it can be used to disable
|
|
restoring the saved data.
|
|
- wxPersistentObject is the base class for all persistent objects or, rather,
|
|
adaptors for the persistent objects as this class main purpose is to provide
|
|
the bridge between the original class -- which has no special persistence
|
|
support -- and wxPersistenceManager,
|
|
- wxPersistentWindow<> which derives from wxPersistentObject and implements some
|
|
of its methods using wxWindow-specific functionality. Notably,
|
|
wxPersistenceManager handles the destruction of persistent windows
|
|
automatically implicitly while it has to be done explicitly for the
|
|
arbitrary persistent objects.
|
|
- wxCreatePersistentObject() function which is used to create the
|
|
appropriate persistence adapter for the object.
|
|
|
|
|
|
@section persistence_using Using Persistent Windows
|
|
|
|
wxWidgets has built-in support for a (constantly growing) number of controls.
|
|
Currently the following classes are supported:
|
|
|
|
- wxTopLevelWindow (and hence wxFrame and wxDialog)
|
|
- wxBookCtrlBase (i.e. wxNotebook, wxListbook, wxToolbook and wxChoicebook)
|
|
- wxTreebook
|
|
|
|
To automatically save and restore the properties of the windows of classes
|
|
listed above you need to:
|
|
|
|
-# Set a unique name for the window using wxWindow::SetName(): this step is
|
|
important as the name is used in the configuration file and so must be
|
|
unique among all windows of the same class.
|
|
-# Call wxPersistenceManager::Register() at any moment after creating the
|
|
window and then wxPersistenceManager::Restore() when the settings may be
|
|
restored (which can't be always done immediately, e.g. often the window
|
|
needs to be populated first). If settings can be restored immediately after
|
|
the window creation, as is often the case for wxTopLevelWindow, for
|
|
example, then wxPersistenceManager::RegisterAndRestore() can be used to do
|
|
both at once.
|
|
-# If you do not want the settings for the window to be saved (for example
|
|
the changes to the dialog size are usually not saved if the dialog was
|
|
cancelled), you need to call wxPersistenceManager::Unregister() manually.
|
|
Otherwise the settings will be automatically saved when the control itself
|
|
is destroyed.
|
|
|
|
Example of using a notebook control which automatically remembers the last open
|
|
page:
|
|
|
|
@code
|
|
wxNotebook *book = new wxNotebook(parent, wxID_ANY);
|
|
book->SetName("MyBook"); // do not use the default name
|
|
book->AddPage(...);
|
|
book->AddPage(...);
|
|
book->AddPage(...);
|
|
if ( !wxPersistenceManager::RegisterAndRestore(book) )
|
|
{
|
|
// nothing was restored, so choose the default page ourselves
|
|
book->SetSelection(0);
|
|
}
|
|
@endcode
|
|
|
|
|
|
@section persistence_defining Defining Custom Persistent Windows
|
|
|
|
User-defined classes can be easily integrated with wxPersistenceManager. To add
|
|
support for your custom class @c MyWidget you just need to:
|
|
|
|
-# Define a new @c MyPersistentWidget class inheriting from
|
|
wxPersistentWindow<MyWidget>.
|
|
-# Implement its pure virtual GetKind() method returning a unique string
|
|
identifying all @c MyWidget objects, typically something like @c "widget"
|
|
-# Implement its pure virtual Save() and Restore() methods to actually save
|
|
and restore the widget settings using wxPersistentObject::SaveValue() and
|
|
wxPersistentObject::RestoreValue() methods.
|
|
-# Define wxCreatePersistentObject() overload taking @c MyWidget * and
|
|
returning a new @c MyPersistentWidget object.
|
|
|
|
If you want to add persistence support for a class not deriving from wxWindow,
|
|
you need to derive @c MyPersistentWidget directly from wxPersistentObject and
|
|
so implement its pure virtual wxPersistentObject::GetName() method too.
|
|
Additionally, you must ensure that wxPersistenceManager::SaveAndUnregister() is
|
|
called when your object is destroyed as this can be only done automatically for
|
|
windows.
|
|
|
|
*/
|