Made section names more globally unique

[wxWidgets.git] / docs / doxygen / overviews / propgrid.h

/////////////////////////////////////////////////////////////////////////////
// Name:        propgrid.h
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id:
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/**

@page overview_propgrid wxPropertyGrid Overview

Key Classes:
@li wxPGProperty
@li wxPropertyGrid
@li wxPropertyGridEvent
@li wxPropertyGridManager
@li wxPropertyGridPage

  wxPropertyGrid is a specialized grid for editing properties such as strings,
numbers, flagsets, fonts, and colours. It is possible, for example, to categorize
properties, set up a complete tree-hierarchy, add multiple columns, and set
arbitrary per-property attributes.

@li @ref propgrid_basics
@li @ref propgrid_categories
@li @ref propgrid_parentprops
@li @ref propgrid_enumandflags
@li @ref propgrid_advprops
@li @ref propgrid_iterating
@li @ref propgrid_operations
@li @ref propgrid_events
@li @ref propgrid_validating
@li @ref propgrid_populating
@li @ref propgrid_cellrender
@li @ref propgrid_customizing
@li @ref propgrid_usage2
@li @ref propgrid_subclassing
@li @ref propgrid_misc
@li @ref propgrid_proplist
@li @ref propgrid_userhelp
@li @ref propgrid_notes
@li @ref propgrid_newprops
@li @ref propgrid_neweditors

@section propgrid_basics Creating and Populating wxPropertyGrid

As seen here, wxPropertyGrid is constructed in the same way as
other wxWidgets controls:

@code

// Necessary header file
#include <wx/propgrid/propgrid.h>

...

    // Assumes code is in frame/dialog constructor

    // Construct wxPropertyGrid control
    wxPropertyGrid* pg = new wxPropertyGrid(
        this, // parent
        PGID, // id
        wxDefaultPosition, // position
        wxDefaultSize, // size
        // Here are just some of the supported window styles
        wxPG_AUTO_SORT | // Automatic sorting after items added
        wxPG_SPLITTER_AUTO_CENTER | // Automatically center splitter until user manually adjusts it
        // Default style
        wxPG_DEFAULT_STYLE );

    // Window style flags are at premium, so some less often needed ones are
    // available as extra window styles (wxPG_EX_xxx) which must be set using
    // SetExtraStyle member function. wxPG_EX_HELP_AS_TOOLTIPS, for instance,
    // allows displaying help strings as tooltips.
    pg->SetExtraStyle( wxPG_EX_HELP_AS_TOOLTIPS );

@endcode

  (for complete list of new window styles: @link wndflags Additional Window Styles@endlink)

  wxPropertyGrid is usually populated with lines like this:

@code
    pg->Append( new wxStringProperty(wxT("Label"),wxT("Name"),wxT("Initial Value")) );
@endcode

Naturally, wxStringProperty is a property class. Only the first function argument (label)
is mandatory. Second one, name, defaults to label and, third, the initial value, to
default value. If constant wxPG_LABEL is used as the name argument, then the label is
automatically used as a name as well (this is more efficient than manually defining both
as the same). Use of empty name is discouraged and will sometimes result in run-time error.
Note that all property class constructors have quite similar constructor argument list.

To demonstrate other common property classes, here's another code snippet:

@code

    // Add int property
    pg->Append( new wxIntProperty(wxT("IntProperty"), wxPG_LABEL, 12345678) );

    // Add float property (value type is actually double)
    pg->Append( new wxFloatProperty(wxT("FloatProperty"), wxPG_LABEL, 12345.678) );

    // Add a bool property
    pg->Append( new wxBoolProperty(wxT("BoolProperty"), wxPG_LABEL, false) );

    // A string property that can be edited in a separate editor dialog.
    pg->Append( new wxLongStringProperty(wxT("LongStringProperty"),
                                         wxPG_LABEL,
                                         wxT("This is much longer string than the ")
                                         wxT("first one. Edit it by clicking the button.")));

    // String editor with dir selector button.
    pg->Append( new wxDirProperty(wxT("DirProperty"), wxPG_LABEL, ::wxGetUserHome()) );

    // wxArrayStringProperty embeds a wxArrayString.
    pg->Append( new wxArrayStringProperty(wxT("Label of ArrayStringProperty"),
                                          wxT("NameOfArrayStringProp")));

    // A file selector property.
    pg->Append( new wxFileProperty(wxT("FileProperty"), wxPG_LABEL, wxEmptyString) );

    // Extra: set wildcard for file property (format same as in wxFileDialog).
    pg->SetPropertyAttribute( wxT("FileProperty"),
                              wxPG_FILE_WILDCARD,
                              wxT("All files (*.*)|*.*") );

@endcode

  Operations on properties should be done either via wxPropertyGrid's
(or wxPropertyGridManager's) methods, or by acquiring pointer to a property
(Append returns a wxPGProperty* or wxPGId, which is typedef for same), and then
calling its method. Note however that property's methods generally do not
automatically update grid graphics.

  Property container functions operating on properties, such as SetPropertyValue or
DisableProperty, all accept a special wxPGPropArg, argument which can automatically
convert name of a property to a pointer. For instance:

@code
    // A file selector property.
    wxPGPropety* p = pg->Append( new wxFileProperty(wxT("FileProperty"), wxPG_LABEL, wxEmptyString) );

    // Valid: Set wildcard by name
    pg->SetPropertyAttribute( wxT("FileProperty"),
                              wxPG_FILE_WILDCARD,
                              wxT("All files (*.*)|*.*") );

    // Also Valid: Set wildcard by ptr
    pg->SetPropertyAttribute( p,
                              wxPG_FILE_WILDCARD,
                              wxT("All files (*.*)|*.*") );
@endcode

Using pointer is faster, since it doesn't require hash map lookup. Anyway, you can allways
get property pointer (wxPGProperty*) as Append/Insert return value, or by calling
GetPropertyByName.

  Below are samples for using some of the more commong operations. See 
wxPropertyGridInterface and wxPropertyGrid class references for complete list.

@code

    // wxPGId is a short-hand for wxPGProperty*. Let's use it this time.
    wxPGId id = pg->GetPropertyByName( wxT("MyProperty") );

    // There are many overloaded versions of this method, of which each accept
    // different type of value.
    pg->SetPropertyValue( wxT("MyProperty"), 200 );

    // Setting a string works for all properties - conversion is done
    // automatically.
    pg->SetPropertyValue( id, wxT("400") );

    // Getting property value as wxVariant.
    wxVariant value = pg->GetPropertyValue( wxT("MyProperty") );

    // Getting property value as String (again, works for all typs).
    wxString value = pg->GetPropertyValueAsString( id );

    // Getting property value as int. Provokes a run-time error
    // if used with property which value type is not "long".
    long value = pg->GetPropertyValueAsLong( wxT("MyProperty") );

    // Set new name.
    pg->SetPropertyName( wxT("MyProperty"), wxT("X") );

    // Set new label - we need to use the new name.
    pg->SetPropertyLabel( wxT("X"), wxT("New Label") );

    // Disable the property. It's text will appear greyed.
    // This is probably the closest you can get if you want
    // a "read-only" property.
    pg->DisableProperty( id );

@endcode


@section propgrid_categories Categories

  wxPropertyGrid has a hierarchial property storage and display model, which
allows property categories to hold child properties and even other
categories. Other than that, from the programmer's point of view, categories
can be treated exactly the same as "other" properties. For example, despite
its name, GetPropertyByName also returns a category by name, and SetPropertyLabel
also sets label of a category. Note however that sometimes the label of a
property category may be referred as caption (for example, there is
SetCaptionForegroundColour method that sets text colour of a property category's label).

  When category is added at the top (i.e. root) level of the hierarchy,
it becomes a *current category*. This means that all other (non-category)
properties after it are automatically added to it. You may add
properties to specific categories by using wxPropertyGrid::Insert or wxPropertyGrid::AppendIn.

  Category code sample:

@code

    // One way to add category (similar to how other properties are added)
    pg->Append( new wxPropertyCategory(wxT("Main")) );

    // All these are added to "Main" category
    pg->Append( new wxStringProperty(wxT("Name")) );
    pg->Append( new wxIntProperty(wxT("Age"),wxPG_LABEL,25) );
    pg->Append( new wxIntProperty(wxT("Height"),wxPG_LABEL,180) );
    pg->Append( new wxIntProperty(wxT("Weight")) );

    // Another one
    pg->Append( new wxPropertyCategory(wxT("Attrikbutes")) );

    // All these are added to "Attributes" category
    pg->Append( new wxIntProperty(wxT("Intelligence")) );
    pg->Append( new wxIntProperty(wxT("Agility")) );
    pg->Append( new wxIntProperty(wxT("Strength")) );

@endcode


@section propgrid_parentprops Tree-like Property Structure

  As a new feature in version 1.3.1, basicly any property can have children. There
are few limitations, however.

@remarks
- Names of properties with non-category, non-root parents are not stored in hash map.
  Instead, they can be accessed with strings like "Parent.Child". For instance, in
  the sample below, child property named "Max. Speed (mph)" can be accessed by global
  name "Car.Speeds.Max Speed (mph)".
- If you want to property's value to be a string composed based on the values of
  child properties, you must use wxStringProperty as parent and use value "<composed>".
- Events (eg. change of value) that occur in parent do not propagate to children. Events
  that occur in children will propagate to parents, but only if they are wxStringProperties
  with "<composed>" value.
- Old wxParentProperty class is deprecated, and remains as a typedef of wxStringProperty.
  If you want old value behavior, you must specify "<composed>" as wxStringProperty's
  value.

Sample:

@code
    wxPGId pid = pg->Append( new wxStringProperty(wxT("Car"),wxPG_LABEL,wxT("<composed>")) );

    pg->AppendIn( pid, new wxStringProperty(wxT("Model"),
                                            wxPG_LABEL,
                                            wxT("Lamborghini Diablo SV")) );

    pg->AppendIn( pid, new wxIntProperty(wxT("Engine Size (cc)"),
                                         wxPG_LABEL,
                                         5707) );

    wxPGId speedId = pg->AppendIn( pid, new wxStringProperty(wxT("Speeds"),wxPG_LABEL,wxT("<composed>")) );
    pg->AppendIn( speedId, new wxIntProperty(wxT("Max. Speed (mph)"),wxPG_LABEL,290) );
    pg->AppendIn( speedId, new wxFloatProperty(wxT("0-100 mph (sec)"),wxPG_LABEL,3.9) );
    pg->AppendIn( speedId, new wxFloatProperty(wxT("1/4 mile (sec)"),wxPG_LABEL,8.6) );

    // Make sure the child properties can be accessed correctly
    pg->SetPropertyValue( wxT("Car.Speeds.Max. Speed (mph)"), 300 );

    pg->AppendIn( pid, new wxIntProperty(wxT("Price ($)"),
                                         wxPG_LABEL,
                                         300000) );
    // Displayed value of "Car" property is now:
    // "Lamborghini Diablo SV; [300; 3.9; 8.6]; 300000"

@endcode

@section propgrid_enumandflags wxEnumProperty and wxFlagsProperty

  wxEnumProperty is used when you want property's (integer or string) value
to be selected from a popup list of choices.

  Creating wxEnumProperty is more complex than those described earlier.
You have to provide list of constant labels, and optionally relevant values
(if label indexes are not sufficient).

@remarks

- Value wxPG_INVALID_VALUE (equals 2147483647 which usually equals INT_MAX) is not
  allowed as value.

A very simple example:

@code

    //
    // Using wxArrayString
    //
    wxArrayString arrDiet;
    arr.Add(wxT("Herbivore"));
    arr.Add(wxT("Carnivore"));
    arr.Add(wxT("Omnivore"));

    pg->Append( new wxEnumProperty(wxT("Diet"),
                                   wxPG_LABEL,
                                   arrDiet) );



    //
    // Using wxChar* array
    //
    const wxChar* arrayDiet[] =
    { wxT("Herbivore"), wxT("Carnivore"), wxT("Omnivore"), NULL };

    pg->Append( new wxEnumProperty(wxT("Diet"),
                                   wxPG_LABEL,
                                   arrayDiet) );


@endcode

Here's extended example using values as well:

@code

    //
    // Using wxArrayString and wxArrayInt
    //
    wxArrayString arrDiet;
    arr.Add(wxT("Herbivore"));
    arr.Add(wxT("Carnivore"));
    arr.Add(wxT("Omnivore"));

    wxArrayInt arrIds;
    arrIds.Add(40);
    arrIds.Add(45);
    arrIds.Add(50);

    // Note that the initial value (the last argument) is the actual value,
    // not index or anything like that. Thus, our value selects "Omnivore".
    pg->Append( new wxEnumProperty(wxT("Diet"),
                                   wxPG_LABEL,
                                   arrDiet,
                                   arrIds,
                                   50));


    //
    // Using wxChar* and long arrays
    //
    const wxChar* array_diet[] =
    { wxT("Herbivore"), wxT("Carnivore"), wxT("Omnivore"), NULL };

    long array_diet_ids[] =
    { 40, 45, 50 };

    // Value can be set from string as well
    pg->Append( new wxEnumProperty(wxT("Diet"),
                                   wxPG_LABEL,
                                   array_diet,
                                   array_diet_ids);

@endcode

  wxPGChoices is a class where wxEnumProperty, and other properties which
  require label storage, actually stores strings and values. It is used
  to facilitiate reference counting, and therefore recommended way of
  adding items when multiple properties share the same set.

  You can use wxPGChoices directly as well, filling it and then passing it
  to the constructor. Infact, if you wish to display bitmaps next to labels,
  your best choice is to use this approach.

@code

    wxPGChoices chs;
    chs.Add(wxT("Herbivore"),40);
    chs.Add(wxT("Carnivore"),45);
    chs.Add(wxT("Omnivore"),50);

    // Let's add an item with bitmap, too
    chs.Add(wxT("None of the above"), wxBitmap(), 60);

    // Note: you can add even whole arrays to wxPGChoices

    pg->Append( new wxEnumProperty(wxT("Diet"),
                                   wxPG_LABEL,
                                   chs) );

    // Add same choices to another property as well - this is efficient due
    // to reference counting
    pg->Append( new wxEnumProperty(wxT("Diet 2"),
                                   wxPG_LABEL,
                                   chs) );

 @endcode

If you later need to change choices used by a property, there is function
for that as well.

@code

    //
    // Example 1: Add one extra item
    wxPGChoices& choices = pg->GetPropertyChoices(wxT("Diet"));
    choices.Add(wxT("Custom"),55);

    //
    // Example 2: Replace all the choices
    wxPGChoices chs;
    chs.Add(wxT("<No valid items yet>"),0);
    pg->SetPropertyChoices(wxT("Diet"),chs);

@endcode

If you want to create your enum properties with simple (label,name,value)
constructor, then you need to create a new property class using one of the
supplied macro pairs. See @ref pgproperty_creating for details.

<b>wxEditEnumProperty</b> is works exactly like wxEnumProperty, except
is uses non-readonly combobox as default editor, and value is stored as
string when it is not any of the choices.

wxFlagsProperty is similar:

@code

    const wxChar* flags_prop_labels[] = { wxT("wxICONIZE"),
        wxT("wxCAPTION"), wxT("wxMINIMIZE_BOX"), wxT("wxMAXIMIZE_BOX"), NULL };

    // this value array would be optional if values matched string indexes
    long flags_prop_values[] = { wxICONIZE, wxCAPTION, wxMINIMIZE_BOX,
        wxMAXIMIZE_BOX };

    pg->Append( new wxFlagsProperty(wxT("Window Style"),
                                    wxPG_LABEL,
                                    flags_prop_labels,
                                    flags_prop_values,
                                    wxDEFAULT_FRAME_STYLE) );

@endcode

wxFlagsProperty can use wxPGChoices just the same way as wxEnumProperty
(and also custom property classes can be created with similar macro pairs).
<b>Note: </b> When changing "choices" (ie. flag labels) of wxFlagsProperty,
you will need to use SetPropertyChoices - otherwise they will not get updated
properly.

@section propgrid_advprops Specialized Properties

  This section describes the use of less often needed property classes.
To use them, you have to include <wx/propgrid/advprops.h>.

@code

// Necessary extra header file
#include <wx/propgrid/advprops.h>

...

    // Date property.
    pg->Append( new wxDateProperty(wxT("MyDateProperty"),
                                   wxPG_LABEL,
                                   wxDateTime::Now()) );

    // Image file property. Wildcard is auto-generated from available
    // image handlers, so it is not set this time.
    pg->Append( new wxImageFileProperty(wxT("Label of ImageFileProperty"),
                                        wxT("NameOfImageFileProp")) );

    // Font property has sub-properties. Note that we give window's font as
    // initial value.
    pg->Append( new wxFontProperty(wxT("Font"),
                                   wxPG_LABEL,
                                   GetFont()) );

    // Colour property with arbitrary colour.
    pg->Append( new wxColourProperty(wxT("My Colour 1"),
                                     wxPG_LABEL,
                                     wxColour(242,109,0) ) );

    // System colour property.
    pg->Append( new wxSystemColourProperty(wxT("My SysColour 1"),
                                           wxPG_LABEL,
                                           wxSystemSettings::GetColour(wxSYS_COLOUR_WINDOW)) );

    // System colour property with custom colour.
    pg->Append( new wxSystemColourProperty(wxT("My SysColour 2"),
                                           wxPG_LABEL,
                                           wxColour(0,200,160) ) );

    // Cursor property
    pg->Append( new wxCursorProperty(wxT("My Cursor"),
                                     wxPG_LABEL,
                                     wxCURSOR_ARROW));

@endcode


@section propgrid_iterating Iterating through a property container

You can use somewhat STL'ish iterator classes to iterate through the grid.
Here is a simple example of forward iterating through all individual
properties (not categories or sub-propeties that are normally 'transparent'
to application code):

@code

    wxPropertyGridIterator it;

    for ( it = pg->GetIterator();
          !it.AtEnd();
          it++ )
    {
        wxPGProperty* p = *it;
        // Do something with the property
    }

@endcode

As expected there is also a const iterator:

@code

    wxPropertyGridConstIterator it;

    for ( it = pg->GetIterator();
          !it.AtEnd();
          it++ )
    {
        const wxPGProperty* p = *it;
        // Do something with the property
    }

@endcode

You can give some arguments to GetIterator to determine which properties
get automatically filtered out. For complete list of options, see
@link iteratorflags List of Property Iterator Flags@endlink. GetIterator()
also accepts other arguments. See wxPropertyGridInterface::GetIterator()
for details.

This example reverse-iterates through all visible items:

@code

    wxPropertyGridIterator it;

    for ( it = pg->GetIterator(wxPG_ITERATE_VISIBLE, wxBOTTOM);
          !it.AtEnd();
          it-- )
    {
        wxPGProperty* p = *it;
        // Do something with the property
    }

@endcode

<b>wxPython Note:</b> Instead of ++ operator, use Next() method, and instead of
* operator, use GetProperty() method.

GetIterator() only works with wxPropertyGrid and the individual pages
of wxPropertyGridManager. In order to iterate through an arbitrary
property container, you need to use wxPropertyGridInterface::GetVIterator().
Note however that this virtual iterater is limited to forward iteration.

@code

    wxPGVIterator it;

    for ( it = manager->GetVIterator();
          !it.AtEnd();
          it.Next() )
    {
        wxPGProperty* p = it.GetProperty();
        // Do something with the property
    }

@endcode


@section propgrid_operations More About Operating with Properties

Getting value of selected wxSystemColourProperty (which value type is derived
from wxObject):

@code

    wxPGId id = pg->GetSelection();

    if ( id )
    {
        // Get name of property
        const wxString& name = pg->GetPropertyName( id );

        // If type is not correct, GetColour() method will produce run-time error
        if ( pg->GetPropertyValueType() == wxT("wxColourPropertyValue") ) )
        {
            wxColourPropertyValue* pcolval =
                wxDynamicCast(pg->GetPropertyValueAsWxObjectPtr(id),
                              wxColourPropertyValue);

            // Report value
            wxString text;
            if ( pcolval->m_type == wxPG_CUSTOM_COLOUR )
                text.Printf( wxT("It is custom colour: (%i,%i,%i)"),
                    (int)pcolval->m_colour.Red(),
                    (int)pcolval->m_colour.Green(),
                    (int)pcolval->m_colour.Blue());
            else
                text.Printf( wxT("It is wx system colour (number=%i): (%i,%i,%i)"),
                    (int)pcolval->m_type,
                    (int)pcolval->m_colour.Red(),
                    (int)pcolval->m_colour.Green(),
                    (int)pcolval->m_colour.Blue());

            wxMessageBox( text );
        }
    }

@endcode

@section propgrid_populating Populating wxPropertyGrid Automatically

@subsection propgrid_fromvariants Populating from List of wxVariants

Example of populating an empty wxPropertyGrid from a values stored
in an arbitrary list of wxVariants.

@code

    // This is a static method that initializes *all* builtin type handlers
    // available, including those for wxColour and wxFont. Refers to *all*
    // included properties, so when compiling with static library, this
    // method may increase the executable size significantly.
    pg->InitAllTypeHandlers();

    // Get contents of the grid as a wxVariant list
    wxVariant all_values = pg->GetPropertyValues();

    // Populate the list with values. If a property with appropriate
    // name is not found, it is created according to the type of variant.
    pg->SetPropertyValues( my_list_variant );

    // In order to get wxObject ptr from a variant value,
    // wxGetVariantCast(VARIANT,CLASSNAME) macro has to be called.
    // Like this:
    wxVariant v_txcol = pg->GetPropertyValue(wxT("Text Colour"));
    const wxColour& txcol = wxGetVariantCast(v_txcol,wxColour);

@endcode

@subsection propgrid_fromfile Loading Population from a Text-based Storage

Class wxPropertyGridPopulator may be helpful when writing code that
loads properties from a text-source. In fact, the supplied xrc handler
(src/xh_propgrid.cpp) uses it. See that code for more info.
NOTE: src/xh_propgrid.cpp is not included in the library by default,
to avoid dependency to wxXRC. You will need to add it to your application
separately.

@subsection propgrid_editablestate Saving and Restoring User-Editable State

You can use wxPGEditableState and wxPGMEditableState classes, and
wxPropertyGrid::SaveEditableState() and wxPropertyGrid::RestoreEditableState()
to save and restore user-editable state (selected property, expanded/
collapsed properties, and scrolled position). For convience with
program configuration, wxPGEditableState has functions to save/load
its value in wxString. For instance:

@code
    // Save state into config
    wxPGEditableState edState;
    pg->SaveEditableState(&edState);
    programConfig->Store(wxT("PropertyGridState"), edState.GetAsString());

    // Restore state from config
    wxPGEditableState edState;
    edState.SetFromString(programConfig->Load(wxT("PropertyGridState")));
    pg->RestoreEditableState(edState);
@endcode


@section propgrid_events Event Handling

Probably the most important event is the Changed event which occurs when
value of any property is changed by the user. Use EVT_PG_CHANGED(id,func)
in your event table to use it.

For complete list of event types, see wxPropertyGrid class reference.

The custom event class, wxPropertyGridEvent, has methods to directly
access the property that triggered the event.

Here's a small sample:

@code

// Portion of an imaginary event table
BEGIN_EVENT_TABLE(MyForm, wxFrame)

    ...

    // This occurs when a property value changes
    EVT_PG_CHANGED( PGID, MyForm::OnPropertyGridChange )

    ...

END_EVENT_TABLE()

void MyForm::OnPropertyGridChange( wxPropertyGridEvent& event )
{
    wxPGProperty *property = event.GetProperty();

    // It may be NULL
    if ( !property )
        return;

    // Get name of changed property
    const wxString& name = property->GetName();

    // Get resulting value
    wxVariant value = property->GetValue();
}

@endcode

Another event type you might find useful is EVT_PG_CHANGING, which occurs
just prior property value is being changed by user. You can acquire pending
value using wxPropertyGridEvent::GetValue(), and if it is not acceptable,
call wxPropertyGridEvent::Veto() to prevent the value change from taking
place.

@code

// Portion of an imaginary event table
BEGIN_EVENT_TABLE(MyForm, wxFrame)

    ...

    // This occurs when a property value changes
    EVT_PG_CHANGING( PGID, MyForm::OnPropertyGridChanging )

    ...

END_EVENT_TABLE()

void MyForm::OnPropertyGridChanging( wxPropertyGridEvent& event )
{
    wxPGProperty* property = event.GetProperty();

    if ( property == m_pWatchThisProperty )
    {
        // GetValue() returns the pending value, but is only
        // supported by wxEVT_PG_CHANGING.
        if ( event.GetValue().GetString() == g_pThisTextIsNotAllowed )
        {
            event.Veto();
            return;
        }
    }
}

@endcode

@remarks On Sub-property Event Handling
- For aggregate type properties (wxFontProperty, wxFlagsProperty, etc), events
  occur for the main parent property only. For other properties events occur
  for the children themselves..

- When property's child gets changed, you can use wxPropertyGridEvent::GetMainParent
  to obtain its topmost non-category parent (useful, if you have deeply nested
  properties).


@section propgrid_validating Validating Property Values

There are various ways to make sure user enters only correct values. First, you
can use wxValidators similar to as you would with ordinary controls. Use
wxPropertyGridInterface::SetPropertyValidator() to assign wxValidator to 
property.

Second, you can subclass a property and override wxPGProperty::ValidateValue(),
or handle wxEVT_PG_CHANGING for the same effect. Both of these methods do not
actually prevent user from temporarily entering invalid text, but they do give
you an opportunity to warn the user and block changed value from being committed
in a property.

Various validation failure options can be controlled globally with
wxPropertyGrid::SetValidationFailureBehavior(), or on an event basis by
calling wxEvent::SetValidationFailureBehavior(). Here's a code snippet of
how to handle wxEVT_PG_CHANGING, and to set custom failure behaviour and
message.

@code
    void MyFrame::OnPropertyGridChanging(wxPropertyGridEvent& event)
    {
        wxPGProperty* property = event.GetProperty();

        // You must use wxPropertyGridEvent::GetValue() to access
        // the value to be validated.
        wxVariant pendingValue = event.GetValue();

        if ( property->GetName() == wxT("Font") )
        {
            // Make sure value is not unspecified
            if ( !pendingValue.IsNull() )
            {
                wxFont font << pendingValue;

                // Let's just allow Arial font
                if ( font.GetFaceName() != wxT("Arial") )
                {
                    event.Veto();
                    event.SetValidationFailureBehavior(wxPG_VFB_STAY_IN_PROPERTY |
                                                       wxPG_VFB_BEEP |
                                                       wxPG_VFB_SHOW_MESSAGE);
                }
            }
        }
    }
@endcode


@section propgrid_cellrender Customizing Individual Cell Appearance

You can control text colour, background colour, and attached image of
each cell in the property grid. Use wxPropertyGridInterface::SetPropertyCell() or
wxPGProperty::SetCell() for this purpose.

In addition, it is possible to control these characteristics for
wxPGChoices list items. See wxPGChoices::Item() and wxPGChoiceEntry class
reference for more info.


@section propgrid_customizing Customizing Properties (without sub-classing)

In this section are presented miscellaneous ways to have custom appearance
and behavior for your properties without all the necessary hassle
of sub-classing a property class etc.

@subsection propgrid_customimage Setting Value Image

Every property can have a small value image placed in front of the
actual value text. Built-in example of this can be seen with
wxColourProperty and wxImageFileProperty, but for others it can
be set using wxPropertyGrid::SetPropertyImage method.

@subsection propgrid_customvalidator Setting Validator

You can set wxValidator for a property using wxPropertyGrid::SetPropertyValidator.

Validator will work just like in wxWidgets (ie. editorControl->SetValidator(validator)
is called).

@subsection propgrid_customeditor Setting Property's Editor Control(s)

You can set editor control (or controls, in case of a control and button),
of any property using wxPropertyGrid::SetPropertyEditor. Editors are passed
using wxPG_EDITOR(EditorName) macro, and valid built-in EditorNames are
TextCtrl, Choice, ComboBox, CheckBox, TextCtrlAndButton, ChoiceAndButton,
SpinCtrl, and DatePickerCtrl. Two last mentioned ones require call to
static member function wxPropertyGrid::RegisterAdditionalEditors().

Following example changes wxColourProperty's editor from default Choice
to TextCtrlAndButton. wxColourProperty has its internal event handling set
up so that button click events of the button will be used to trigger
colour selection dialog.

@code

    wxPGId colProp = pg->Append(wxColourProperty(wxT("Text Colour")));

    pg->SetPropertyEditor(colProp,wxPG_EDITOR(TextCtrlAndButton));

@endcode

Naturally, creating and setting custom editor classes is a possibility as
well. For more information, see wxPGEditor class reference.

@subsection propgrid_editorattrs Property Attributes Recognized by Editors

<b>SpinCtrl</b> editor can make use of property's "Min", "Max", "Step" and "Wrap" attributes.

@subsection propgrid_multiplebuttons Adding Multiple Buttons Next to an Editor

See wxPGMultiButton class reference.

@subsection propgrid_customeventhandling Handling Events Passed from Properties

<b>wxEVT_COMMAND_BUTTON_CLICKED </b>(corresponds to event table macro EVT_BUTTON):
Occurs when editor button click is not handled by the property itself
(as is the case, for example, if you set property's editor to TextCtrlAndButton
from the original TextCtrl).

@subsection propgrid_attributes Property Attributes

Miscellaneous values, often specific to a property type, can be set
using wxPropertyGrid::SetPropertyAttribute and wxPropertyGrid::SetPropertyAttributeAll
methods.

Attribute names are strings and values wxVariant. Arbitrary names are allowed
inorder to store user values. Constant equivalents of all attribute string names are
provided. Some of them are defined as cached strings, so using constants can provide
for smaller binary size.

For complete list of attributes, see @link attrids Property Attributes@endlink.

@subsection propgrid_boolcheckbox Setting wxBoolProperties to Use Check Box

To have all wxBoolProperties to use CheckBox editor instead of Choice, use
following (call after bool properties have been added):

@code
    pg->SetPropertyAttributeAll(wxPG_BOOL_USE_CHECKBOX,true);
@endcode


@section propgrid_usage2 Using wxPropertyGridManager

wxPropertyGridManager is an efficient multi-page version of wxPropertyGrid,
which can optionally have toolbar for mode and page selection, and a help text
box.

wxPropertyGridManager inherits from wxPropertyGridInterface, and as such
it has most property manipulation functions. However, only some of them affect
properties on all pages (eg. GetPropertyByName() and ExpandAll()), while some
(eg. Append()) only apply to the currently selected page.

To operate explicitly on properties on specific page, use wxPropertyGridManager::GetPage()
to obtain pointer to page's wxPropertyGridPage object.

Visual methods, such as SetCellBackgroundColour and GetNextVisible are only
available in wxPropertyGrid. Use wxPropertyGridManager::GetGrid() to obtain
pointer to it.

Iteration methods will not work in wxPropertyGridManager. Instead, you must acquire
the internal grid (GetGrid()) or wxPropertyGridPage object (GetPage()).

wxPropertyGridManager constructor has exact same format as wxPropertyGrid
constructor, and basicly accepts same extra window style flags (albeit also
has some extra ones).

Here's some example code for creating and populating a wxPropertyGridManager:

@code

    wxPropertyGridManager* pgMan = new wxPropertyGridManager(this, PGID,
        wxDefaultPosition, wxDefaultSize,
        // These and other similar styles are automatically
        // passed to the embedded wxPropertyGrid.
        wxPG_BOLD_MODIFIED|wxPG_SPLITTER_AUTO_CENTER|
        // Include toolbar.
        wxPG_TOOLBAR |
        // Include description box.
        wxPG_DESCRIPTION |
        // Include compactor.
        wxPG_COMPACTOR |
        // Plus defaults.
        wxPGMAN_DEFAULT_STYLE
       );

    wxPropertyGridPage* page;

    // Adding a page sets target page to the one added, so
    // we don't have to call SetTargetPage if we are filling
    // it right after adding.
    pgMan->AddPage(wxT("First Page"));
    page = pgMan->GetLastPage();

    page->Append( new wxPropertyCategory(wxT("Category A1")) );

    page->Append( new wxIntProperty(wxT("Number"),wxPG_LABEL,1) );

    page->Append( new wxColourProperty(wxT("Colour"),wxPG_LABEL,*wxWHITE) );

    pgMan->AddPage(wxT("Second Page"));
    page = pgMan->GetLastPage();

    page->Append( wxT("Text"),wxPG_LABEL,wxT("(no text)") );

    page->Append( new wxFontProperty(wxT("Font"),wxPG_LABEL) );

@endcode

@subsection propgrid_propgridpage wxPropertyGridPage

wxPropertyGridPage is holder of properties for one page in manager. It is derived from
wxEvtHandler, so you can subclass it to process page-specific property grid events. Hand
over your page instance in wxPropertyGridManager::AddPage.

Please note that the wxPropertyGridPage itself only sports subset of wxPropertyGrid API
(but unlike manager, this include item iteration). Naturally it inherits from
wxPropertyGridMethods and wxPropertyGridPageState.


@section propgrid_subclassing Subclassing wxPropertyGrid and wxPropertyGridManager

Few things to note:

- Only a small percentage of member functions are virtual. If you need more,
  just e-mail to wx-dev mailing list.

- Data manipulation is done in wxPropertyGridPageState class. So, instead of
  overriding wxPropertyGrid::Insert, you'll probably want to override wxPropertyGridPageState::DoInsert.

- Override wxPropertyGrid::CreateState to instantiate your derivate wxPropertyGridPageState.
  For wxPropertyGridManager, you'll need to subclass wxPropertyGridPage instead (since it
  is derived from wxPropertyGridPageState), and hand over instances in wxPropertyGridManager::AddPage
  calls.

- You can use a derivate wxPropertyGrid with manager by overriding wxPropertyGridManager::CreatePropertyGrid
  member function.


@section propgrid_misc Miscellaneous Topics

@subsection propgrid_namescope Property Name Scope

  All properties which parent is category or root can be accessed
directly by their base name (ie. name given for property in its constructor).
Other properties can be accessed via "ParentsName.BaseName" notation,
Naturally, all property names should be unique.

@subsection propgrid_nonuniquelabels Non-unique Labels

  It is possible to have properties with identical label under same parent.
However, care must be taken to ensure that each property still has
unique (base) name.

@subsection propgrid_boolproperty wxBoolProperty

  There are few points about wxBoolProperty that require futher discussion:
  - wxBoolProperty can be shown as either normal combobox or as a checkbox.
    Property attribute wxPG_BOOL_USE_CHECKBOX is used to change this.
    For example, if you have a wxFlagsProperty, you can
    set its all items to use check box using the following:
    @code
        pg->SetPropertyAttribute(wxT("MyFlagsProperty"),wxPG_BOOL_USE_CHECKBOX,true,wxPG_RECURSE);
    @endcode

  - Default item names for wxBoolProperty are [wxT("False"),wxT("True")]. This can be
    changed using wxPropertyGrid::SetBoolChoices(trueChoice,falseChoice).

@subsection propgrid_textctrlupdates Updates from wxTextCtrl Based Editor

  Changes from wxTextCtrl based property editors are committed (ie.
wxEVT_PG_CHANGED is sent etc.) *only* when (1) user presser enter, (2)
user moves to edit another property, or (3) when focus leaves
the grid.

  Because of this, you may find it useful, in some apps, to call
wxPropertyGrid::CommitChangesFromEditor() just before you need to do any
computations based on property grid values. Note that CommitChangesFromEditor()
will dispatch wxEVT_PG_CHANGED with ProcessEvent, so any of your event handlers
will be called immediately.

@subsection propgrid_splittercentering Centering the Splitter

  If you need to center the splitter, but only once when the program starts,
then do <b>not</b> use the wxPG_SPLITTER_AUTO_CENTER window style, but the
wxPropertyGrid::CenterSplitter() method. <b>However, be sure to call it after
the sizer setup and SetSize calls!</b> (ie. usually at the end of the
frame/dialog constructor)

@subsection propgrid_splittersetting Setting Splitter Position When Creating Property Grid

Splitter position cannot exceed grid size, and therefore setting it during
form creation may fail as initial grid size is often smaller than desired
splitter position, especially when sizers are being used.

@subsection propgrid_colourproperty wxColourProperty and wxSystemColourProperty

Through subclassing, these two property classes provide substantial customization
features. Subclass wxSystemColourProperty if you want to use wxColourPropertyValue
(which features colour type in addition to wxColour), and wxColourProperty if plain
wxColour is enough.

Override wxSystemColourProperty::ColourToString() to redefine how colours are
printed as strings.

Override wxSystemColourProperty::GetCustomColourIndex() to redefine location of
the item that triggers colour picker dialog (default is last).

Override wxSystemColourProperty::GetColour() to determine which colour matches
which choice entry.

@section propgrid_proplist Property Class Descriptions

See @ref pgproperty_properties

*/