Version: 3.1.0

#include <wx/app.h>

+ Inheritance diagram for wxApp:

Detailed Description

The wxApp class represents the application itself when wxUSE_GUI=1.

In addition to the features provided by wxAppConsole it keeps track of the top window (see SetTopWindow()) and adds support for video modes (see SetVideoMode()).

In general, application-wide settings for GUI-only apps are accessible from wxApp (or from wxSystemSettings or wxSystemOptions classes).

Events emitted by this class

Event macros for events emitted by this class:

  • EVT_QUERY_END_SESSION(func):
    Process a query end session event, supplying the member function. See wxCloseEvent.
  • EVT_END_SESSION(func):
    Process an end session event, supplying the member function. See wxCloseEvent.
  • EVT_ACTIVATE_APP(func):
    Process a wxEVT_ACTIVATE_APP event. See wxActivateEvent.
  • EVT_HIBERNATE(func):
    Process a hibernate event. See wxActivateEvent.
  • EVT_DIALUP_CONNECTED(func):
    A connection with the network was established. See wxDialUpEvent.
  • EVT_DIALUP_DISCONNECTED(func):
    The connection with the network was lost. See wxDialUpEvent.
  • EVT_IDLE(func):
    Process a wxEVT_IDLE event. See wxIdleEvent.

Library:  wxBase
Category:  Application and Process Management
See also
wxApp Overview, wxAppTraits, wxEventLoopBase, wxSystemSettings

Public Member Functions

 wxApp ()
 Constructor. More...
 
virtual ~wxApp ()
 Destructor. More...
 
virtual wxVideoMode GetDisplayMode () const
 Get display mode that is used use. More...
 
bool GetExitOnFrameDelete () const
 Returns true if the application will exit when the top-level frame is deleted. More...
 
virtual wxLayoutDirection GetLayoutDirection () const
 Return the layout direction for the current locale or wxLayout_Default if it's unknown. More...
 
bool GetUseBestVisual () const
 Returns true if the application will use the best visual on systems that support different visuals, false otherwise. More...
 
virtual wxWindowGetTopWindow () const
 Returns a pointer to the top window. More...
 
virtual bool IsActive () const
 Returns true if the application is active, i.e. if one of its windows is currently in the foreground. More...
 
virtual bool SafeYield (wxWindow *win, bool onlyIfNeeded)
 This function is similar to wxYield(), except that it disables the user input to all program windows before calling wxAppConsole::Yield and re-enables it again afterwards. More...
 
virtual bool SafeYieldFor (wxWindow *win, long eventsToProcess)
 Works like SafeYield() with onlyIfNeeded == true except that it allows the caller to specify a mask of events to be processed. More...
 
bool ProcessMessage (WXMSG *msg)
 Windows-only function for processing a message. More...
 
virtual bool SetDisplayMode (const wxVideoMode &info)
 Set display mode to use. More...
 
void SetExitOnFrameDelete (bool flag)
 Allows the programmer to specify whether the application will exit when the top-level frame is deleted. More...
 
virtual bool SetNativeTheme (const wxString &theme)
 Allows runtime switching of the UI environment theme. More...
 
void SetTopWindow (wxWindow *window)
 Sets the 'top' window. More...
 
void SetUseBestVisual (bool flag, bool forceTrueColour=false)
 Allows the programmer to specify whether the application will use the best visual on systems that support several visual on the same display. More...
 
Mac-specific functions
virtual void MacNewFile ()
 Called in response of an "open-application" Apple event. More...
 
virtual void MacOpenFiles (const wxArrayString &fileNames)
 Called in response of an openFiles message. More...
 
virtual void MacOpenFile (const wxString &fileName)
 Called in response of an "open-document" Apple event. More...
 
virtual void MacOpenURL (const wxString &url)
 Called in response of a "get-url" Apple event. More...
 
virtual void MacPrintFile (const wxString &fileName)
 Called in response of a "print-document" Apple event. More...
 
virtual void MacReopenApp ()
 Called in response of a "reopen-application" Apple event. More...
 
virtual bool OSXIsGUIApplication ()
 May be overridden to indicate that the application is not a foreground GUI application under OS X. More...
 
- Public Member Functions inherited from wxAppConsole
virtual ~wxAppConsole ()
 Destructor. More...
 
bool Yield (bool onlyIfNeeded=false)
 Yields control to pending messages in the event loop. More...
 
void SetCLocale ()
 Sets the C locale to the default locale for the current environment. More...
 
virtual int MainLoop ()
 Called by wxWidgets on creation of the application. More...
 
virtual void ExitMainLoop ()
 Call this to explicitly exit the main message (event) loop. More...
 
virtual int FilterEvent (wxEvent &event)
 Overridden wxEventFilter method. More...
 
wxEventLoopBaseGetMainLoop () const
 Returns the main event loop instance, i.e. the event loop which is started by OnRun() and which dispatches all events sent from the native toolkit to the application (except when new event loops are temporarily set-up). More...
 
virtual void HandleEvent (wxEvtHandler *handler, wxEventFunction func, wxEvent &event) const
 This function simply invokes the given method func of the specified event handler handler with the event as parameter. More...
 
virtual bool UsesEventLoop () const
 Returns true if the application is using an event loop. More...
 
virtual void ProcessPendingEvents ()
 Process all pending events; it is necessary to call this function to process events posted with wxEvtHandler::QueueEvent or wxEvtHandler::AddPendingEvent. More...
 
void DeletePendingEvents ()
 Deletes the pending events of all wxEvtHandlers of this application. More...
 
bool HasPendingEvents () const
 Returns true if there are pending events on the internal pending event list. More...
 
void SuspendProcessingOfPendingEvents ()
 Temporary suspends processing of the pending events. More...
 
void ResumeProcessingOfPendingEvents ()
 Resume processing of the pending events previously stopped because of a call to SuspendProcessingOfPendingEvents(). More...
 
void ScheduleForDestruction (wxObject *object)
 Delayed objects destruction. More...
 
bool IsScheduledForDestruction (wxObject *object) const
 Check if the object had been scheduled for destruction with ScheduleForDestruction(). More...
 
virtual void OnAssertFailure (const wxChar *file, int line, const wxChar *func, const wxChar *cond, const wxChar *msg)
 This function is called when an assert failure occurs, i.e. the condition specified in wxASSERT() macro evaluated to false. More...
 
virtual bool OnCmdLineError (wxCmdLineParser &parser)
 Called when command line parsing fails (i.e. an incorrect command line option was specified by the user). More...
 
virtual bool OnCmdLineHelp (wxCmdLineParser &parser)
 Called when the help option (–help) was specified on the command line. More...
 
virtual bool OnCmdLineParsed (wxCmdLineParser &parser)
 Called after the command line had been successfully parsed. More...
 
virtual void OnEventLoopEnter (wxEventLoopBase *loop)
 Called by wxEventLoopBase::SetActive(): you can override this function and put here the code which needs an active event loop. More...
 
virtual void OnEventLoopExit (wxEventLoopBase *loop)
 Called by wxEventLoopBase::OnExit() for each event loop which is exited. More...
 
virtual int OnExit ()
 Override this member function for any processing which needs to be done as the application is about to exit. More...
 
virtual void OnFatalException ()
 This function may be called if something fatal happens: an unhandled exception under Win32 or a fatal signal under Unix, for example. More...
 
virtual bool OnInit ()
 This must be provided by the application, and will usually create the application's main window, optionally calling SetTopWindow(). More...
 
virtual void OnInitCmdLine (wxCmdLineParser &parser)
 Called from OnInit() and may be used to initialize the parser with the command line options for this application. More...
 
virtual int OnRun ()
 This virtual function is where the execution of a program written in wxWidgets starts. More...
 
virtual bool OnExceptionInMainLoop ()
 This function is called if an unhandled exception occurs inside the main application event loop. More...
 
virtual void OnUnhandledException ()
 This function is called when an unhandled C++ exception occurs in user code called by wxWidgets. More...
 
virtual bool StoreCurrentException ()
 Method to store exceptions not handled by OnExceptionInMainLoop(). More...
 
virtual void RethrowStoredException ()
 Method to rethrow exceptions stored by StoreCurrentException(). More...
 
wxString GetAppDisplayName () const
 Returns the user-readable application name. More...
 
wxString GetAppName () const
 Returns the application name. More...
 
wxString GetClassName () const
 Gets the class name of the application. More...
 
wxAppTraitsGetTraits ()
 Returns a pointer to the wxAppTraits object for the application. More...
 
const wxStringGetVendorDisplayName () const
 Returns the user-readable vendor name. More...
 
const wxStringGetVendorName () const
 Returns the application's vendor name. More...
 
void SetAppDisplayName (const wxString &name)
 Set the application name to be used in the user-visible places such as window titles. More...
 
void SetAppName (const wxString &name)
 Sets the name of the application. More...
 
void SetClassName (const wxString &name)
 Sets the class name of the application. More...
 
void SetVendorDisplayName (const wxString &name)
 Set the vendor name to be used in the user-visible places. More...
 
void SetVendorName (const wxString &name)
 Sets the name of application's vendor. More...
 
- Public Member Functions inherited from wxEvtHandler
 wxEvtHandler ()
 Constructor. More...
 
virtual ~wxEvtHandler ()
 Destructor. More...
 
virtual void QueueEvent (wxEvent *event)
 Queue event for a later processing. More...
 
virtual void AddPendingEvent (const wxEvent &event)
 Post an event to be processed later. More...
 
template<typename T , typename T1 , ... >
void CallAfter (void(T::*method)(T1,...), T1 x1,...)
 Asynchronously call the given method. More...
 
template<typename T >
void CallAfter (const T &functor)
 Asynchronously call the given functor. More...
 
virtual bool ProcessEvent (wxEvent &event)
 Processes an event, searching event tables and calling zero or more suitable event handler function(s). More...
 
bool ProcessEventLocally (wxEvent &event)
 Try to process the event in this handler and all those chained to it. More...
 
bool SafelyProcessEvent (wxEvent &event)
 Processes an event by calling ProcessEvent() and handles any exceptions that occur in the process. More...
 
void ProcessPendingEvents ()
 Processes the pending events previously queued using QueueEvent() or AddPendingEvent(); you must call this function only if you are sure there are pending events for this handler, otherwise a wxCHECK will fail. More...
 
void DeletePendingEvents ()
 Deletes all events queued on this event handler using QueueEvent() or AddPendingEvent(). More...
 
virtual bool SearchEventTable (wxEventTable &table, wxEvent &event)
 Searches the event table, executing an event handler function if an appropriate one is found. More...
 
void Connect (int id, int lastId, wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 Connects the given function dynamically with the event handler, id and event type. More...
 
void Connect (int id, wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Connect(int, int, wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
void Connect (wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Connect(int, int, wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
bool Disconnect (wxEventType eventType, wxObjectEventFunction function, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 Disconnects the given function dynamically from the event handler, using the specified parameters as search criteria and returning true if a matching function has been found and removed. More...
 
bool Disconnect (int id=wxID_ANY, wxEventType eventType=wxEVT_NULL, wxObjectEventFunction function=NULL, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Disconnect(wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
bool Disconnect (int id, int lastId, wxEventType eventType, wxObjectEventFunction function=NULL, wxObject *userData=NULL, wxEvtHandler *eventSink=NULL)
 See the Disconnect(wxEventType, wxObjectEventFunction, wxObject*, wxEvtHandler*) overload for more info. More...
 
template<typename EventTag , typename Functor >
void Bind (const EventTag &eventType, Functor functor, int id=wxID_ANY, int lastId=wxID_ANY, wxObject *userData=NULL)
 Binds the given function, functor or method dynamically with the event. More...
 
template<typename EventTag , typename Class , typename EventArg , typename EventHandler >
void Bind (const EventTag &eventType, void(Class::*method)(EventArg &), EventHandler *handler, int id=wxID_ANY, int lastId=wxID_ANY, wxObject *userData=NULL)
 See the Bind<>(const EventTag&, Functor, int, int, wxObject*) overload for more info. More...
 
template<typename EventTag , typename Functor >
bool Unbind (const EventTag &eventType, Functor functor, int id=wxID_ANY, int lastId=wxID_ANY, wxObject *userData=NULL)
 Unbinds the given function, functor or method dynamically from the event handler, using the specified parameters as search criteria and returning true if a matching function has been found and removed. More...
 
template<typename EventTag , typename Class , typename EventArg , typename EventHandler >
bool Unbind (const EventTag &eventType, void(Class::*method)(EventArg &), EventHandler *handler, int id=wxID_ANY, int lastId=wxID_ANY, wxObject *userData=NULL)
 See the Unbind<>(const EventTag&, Functor, int, int, wxObject*) overload for more info. More...
 
void * GetClientData () const
 Returns user-supplied client data. More...
 
wxClientDataGetClientObject () const
 Returns a pointer to the user-supplied client data object. More...
 
void SetClientData (void *data)
 Sets user-supplied client data. More...
 
void SetClientObject (wxClientData *data)
 Set the client data object. More...
 
bool GetEvtHandlerEnabled () const
 Returns true if the event handler is enabled, false otherwise. More...
 
wxEvtHandlerGetNextHandler () const
 Returns the pointer to the next handler in the chain. More...
 
wxEvtHandlerGetPreviousHandler () const
 Returns the pointer to the previous handler in the chain. More...
 
void SetEvtHandlerEnabled (bool enabled)
 Enables or disables the event handler. More...
 
virtual void SetNextHandler (wxEvtHandler *handler)
 Sets the pointer to the next handler. More...
 
virtual void SetPreviousHandler (wxEvtHandler *handler)
 Sets the pointer to the previous handler. More...
 
void Unlink ()
 Unlinks this event handler from the chain it's part of (if any); then links the "previous" event handler to the "next" one (so that the chain won't be interrupted). More...
 
bool IsUnlinked () const
 Returns true if the next and the previous handler pointers of this event handler instance are NULL. More...
 
- Public Member Functions inherited from wxObject
 wxObject ()
 Default ctor; initializes to NULL the internal reference data. More...
 
 wxObject (const wxObject &other)
 Copy ctor. More...
 
virtual ~wxObject ()
 Destructor. More...
 
virtual wxClassInfoGetClassInfo () const
 This virtual function is redefined for every class that requires run-time type information, when using the wxDECLARE_CLASS macro (or similar). More...
 
wxObjectRefDataGetRefData () const
 Returns the wxObject::m_refData pointer, i.e. the data referenced by this object. More...
 
bool IsKindOf (const wxClassInfo *info) const
 Determines whether this class is a subclass of (or the same class as) the given class. More...
 
bool IsSameAs (const wxObject &obj) const
 Returns true if this object has the same data pointer as obj. More...
 
void Ref (const wxObject &clone)
 Makes this object refer to the data in clone. More...
 
void SetRefData (wxObjectRefData *data)
 Sets the wxObject::m_refData pointer. More...
 
void UnRef ()
 Decrements the reference count in the associated data, and if it is zero, deletes the data. More...
 
void UnShare ()
 This is the same of AllocExclusive() but this method is public. More...
 
void operator delete (void *buf)
 The delete operator is defined for debugging versions of the library only, when the identifier WXDEBUG is defined. More...
 
void * operator new (size_t size, const wxString &filename=NULL, int lineNum=0)
 The new operator is defined for debugging versions of the library only, when the identifier WXDEBUG is defined. More...
 
- Public Member Functions inherited from wxEventFilter
 wxEventFilter ()
 Default constructor. More...
 
virtual ~wxEventFilter ()
 Destructor. More...
 

Additional Inherited Members

- Public Types inherited from wxEventFilter
enum  {
  Event_Skip = -1,
  Event_Ignore = 0,
  Event_Processed = 1
}
 Possible return values for FilterEvent(). More...
 
- Static Public Member Functions inherited from wxAppConsole
static void SetInstance (wxAppConsole *app)
 Allows external code to modify global wxTheApp, but you should really know what you're doing if you call it. More...
 
static wxAppConsoleGetInstance ()
 Returns the one and only global application object. More...
 
static bool IsMainLoopRunning ()
 Returns true if the main event loop is currently running, i.e. if the application is inside OnRun(). More...
 
- Static Public Member Functions inherited from wxEvtHandler
static void AddFilter (wxEventFilter *filter)
 Add an event filter whose FilterEvent() method will be called for each and every event processed by wxWidgets. More...
 
static void RemoveFilter (wxEventFilter *filter)
 Remove a filter previously installed with AddFilter(). More...
 
- Public Attributes inherited from wxAppConsole
int argc
 Number of command line arguments (after environment-specific processing). More...
 
wxChar ** argv
 Command line arguments (after environment-specific processing). More...
 
- Protected Member Functions inherited from wxAppConsole
virtual wxAppTraitsCreateTraits ()
 Creates the wxAppTraits object when GetTraits() needs it for the first time. More...
 
- Protected Member Functions inherited from wxEvtHandler
virtual bool TryBefore (wxEvent &event)
 Method called by ProcessEvent() before examining this object event tables. More...
 
virtual bool TryAfter (wxEvent &event)
 Method called by ProcessEvent() as last resort. More...
 
- Protected Member Functions inherited from wxObject
void AllocExclusive ()
 Ensure that this object's data is not shared with any other object. More...
 
virtual wxObjectRefDataCreateRefData () const
 Creates a new instance of the wxObjectRefData-derived class specific to this object and returns it. More...
 
virtual wxObjectRefDataCloneRefData (const wxObjectRefData *data) const
 Creates a new instance of the wxObjectRefData-derived class specific to this object and initializes it copying data. More...
 
- Protected Attributes inherited from wxObject
wxObjectRefDatam_refData
 Pointer to an object which is the object's reference-counted data. More...
 

Constructor & Destructor Documentation

wxApp::wxApp ( )

Constructor.

Called implicitly with a definition of a wxApp object.

virtual wxApp::~wxApp ( )
virtual

Destructor.

Will be called implicitly on program exit if the wxApp object is created on the stack.

Member Function Documentation

virtual wxVideoMode wxApp::GetDisplayMode ( ) const
virtual

Get display mode that is used use.

This is only used in framebuffer wxWidgets ports such as wxDFB.

bool wxApp::GetExitOnFrameDelete ( ) const

Returns true if the application will exit when the top-level frame is deleted.

See also
SetExitOnFrameDelete()
virtual wxLayoutDirection wxApp::GetLayoutDirection ( ) const
virtual

Return the layout direction for the current locale or wxLayout_Default if it's unknown.

virtual wxWindow* wxApp::GetTopWindow ( ) const
virtual

Returns a pointer to the top window.

Remarks
If the top window hasn't been set using SetTopWindow(), this function will find the first top-level window (frame or dialog or instance of wxTopLevelWindow) from the internal top level window list and return that.
See also
SetTopWindow()
bool wxApp::GetUseBestVisual ( ) const

Returns true if the application will use the best visual on systems that support different visuals, false otherwise.

See also
SetUseBestVisual()
virtual bool wxApp::IsActive ( ) const
virtual

Returns true if the application is active, i.e. if one of its windows is currently in the foreground.

If this function returns false and you need to attract users attention to the application, you may use wxTopLevelWindow::RequestUserAttention to do it.

virtual void wxApp::MacNewFile ( )
virtual

Called in response of an "open-application" Apple event.

Override this to create a new document in your app.

Availability:  only available for the wxOSX/Cocoa port.
virtual void wxApp::MacOpenFile ( const wxString fileName)
virtual

Called in response of an "open-document" Apple event.

Deprecated:
This function is kept mostly for backwards compatibility. Please override wxApp::MacOpenFiles method instead in any new code.
Availability:  only available for the wxOSX/Cocoa port.
virtual void wxApp::MacOpenFiles ( const wxArrayString fileNames)
virtual

Called in response of an openFiles message.

You need to override this method in order to open one or more document files after the user double clicked on it or if the files and/or folders were dropped on either the application in the dock or the application icon in Finder.

By default this method calls MacOpenFile for each file/folder.

Availability:  only available for the wxOSX/Cocoa port.
Since
2.9.3
virtual void wxApp::MacOpenURL ( const wxString url)
virtual

Called in response of a "get-url" Apple event.

Availability:  only available for the wxOSX/Cocoa port.
virtual void wxApp::MacPrintFile ( const wxString fileName)
virtual

Called in response of a "print-document" Apple event.

Availability:  only available for the wxOSX/Cocoa port.
virtual void wxApp::MacReopenApp ( )
virtual

Called in response of a "reopen-application" Apple event.

Availability:  only available for the wxOSX/Cocoa port.
virtual bool wxApp::OSXIsGUIApplication ( )
virtual

May be overridden to indicate that the application is not a foreground GUI application under OS X.

This method is called during the application startup and returns true by default. In this case, wxWidgets ensures that the application is ran as a foreground, GUI application so that the user can interact with it normally, even if it is not bundled. If this is undesired, i.e. if the application doesn't need to be brought to the foreground, this method can be overridden to return false.

Notice that overriding it doesn't make any difference for the bundled applications which are always foreground unless LSBackgroundOnly key is specified in the Info.plist file.

Availability:  only available for the wxOSX/Cocoa port.
Since
3.0.1
bool wxApp::ProcessMessage ( WXMSG *  msg)

Windows-only function for processing a message.

This function is called from the main message loop, checking for windows that may wish to process it.

The function returns true if the message was processed, false otherwise. If you use wxWidgets with another class library with its own message loop, you should make sure that this function is called to allow wxWidgets to receive messages. For example, to allow co-existence with the Microsoft Foundation Classes, override the PreTranslateMessage function:

// Provide wxWidgets message loop compatibility
BOOL CTheApp::PreTranslateMessage(MSG *msg)
{
if (wxTheApp && wxTheApp->ProcessMessage((WXMSW *)msg))
return true;
else
return CWinApp::PreTranslateMessage(msg);
}
Availability:  only available for the wxMSW port.
virtual bool wxApp::SafeYield ( wxWindow win,
bool  onlyIfNeeded 
)
virtual

This function is similar to wxYield(), except that it disables the user input to all program windows before calling wxAppConsole::Yield and re-enables it again afterwards.

If win is not NULL, this window will remain enabled, allowing the implementation of some limited user interaction. Returns the result of the call to wxAppConsole::Yield.

See also
wxSafeYield
virtual bool wxApp::SafeYieldFor ( wxWindow win,
long  eventsToProcess 
)
virtual

Works like SafeYield() with onlyIfNeeded == true except that it allows the caller to specify a mask of events to be processed.

See wxAppConsole::YieldFor for more info.

virtual bool wxApp::SetDisplayMode ( const wxVideoMode info)
virtual

Set display mode to use.

This is only used in framebuffer wxWidgets ports such as wxDFB.

void wxApp::SetExitOnFrameDelete ( bool  flag)

Allows the programmer to specify whether the application will exit when the top-level frame is deleted.

Parameters
flagIf true (the default), the application will exit when the top-level frame is deleted. If false, the application will continue to run.
See also
GetExitOnFrameDelete(), Application Shutdown
virtual bool wxApp::SetNativeTheme ( const wxString theme)
virtual

Allows runtime switching of the UI environment theme.

Currently implemented for wxGTK2-only. Return true if theme was successfully changed.

Parameters
themeThe name of the new theme or an absolute path to a gtkrc-theme-file
void wxApp::SetTopWindow ( wxWindow window)

Sets the 'top' window.

You can call this from within OnInit() to let wxWidgets know which is the main window. You don't have to set the top window; it is only a convenience so that (for example) certain dialogs without parents can use a specific window as the top window.

If no top window is specified by the application, wxWidgets just uses the first frame or dialog (or better, any wxTopLevelWindow) in its top-level window list, when it needs to use the top window. If you previously called SetTopWindow() and now you need to restore this automatic behaviour you can call

.

Parameters
windowThe new top window.
See also
GetTopWindow(), OnInit()
void wxApp::SetUseBestVisual ( bool  flag,
bool  forceTrueColour = false 
)

Allows the programmer to specify whether the application will use the best visual on systems that support several visual on the same display.

This is typically the case under Solaris and IRIX, where the default visual is only 8-bit whereas certain applications are supposed to run in TrueColour mode.

Note that this function has to be called in the constructor of the wxApp instance and won't have any effect when called later on. This function currently only has effect under GTK.

Parameters
flagIf true, the app will use the best visual.
forceTrueColourIf true then the application will try to force using a TrueColour visual and abort the app if none is found.