## wxApp

The wxApp class represents the application itself. It is used to:

- set and get application-wide properties;
- implement the windowing system message or event loop;
- initiate application processing via wxApp::OnInit;
- allow default processing of events not handled by other objects in the application.

You should use the macro IMPLEMENT_APP(appClass) in your application implementation file to tell wxWindows how to create an instance of your application class.

Use DECLARE_APP(appClass) in a header file if you want the wxGetApp function (which returns a reference to your application object) to be visible to other files.

Derived from

wxEvtHandler
wxObject

Include files

<wx/app.h>

See also

wxApp overview

Members

wxApp::wxApp
wxApp::~wxApp
wxApp::argc
wxApp::argv
wxApp::CreateLogTarget
wxApp::Dispatch
wxApp::FilterEvent
wxApp::GetAppName
wxApp::GetAuto3D
wxApp::GetClassName
wxApp::GetExitOnFrameDelete
wxApp::GetTopWindow
wxApp::GetUseBestVisual
wxApp::GetVendorName
wxApp::ExitMainLoop
wxApp::Initialized
wxApp::MainLoop
wxApp::OnAssert
wxApp::OnExit
wxApp::OnCmdLineError
wxApp::OnCmdLineHelp
wxApp::OnCmdLineParsed
wxApp::OnFatalException
wxApp::OnInit
wxApp::OnInitCmdLine
wxApp::OnQueryEndSession
wxApp::ProcessMessage
wxApp::Pending
wxApp::SendIdleEvents
wxApp::SetAppName
wxApp::SetAuto3D
wxApp::SetClassName
wxApp::SetExitOnFrameDelete
wxApp::SetTopWindow
wxApp::SetVendorName
wxApp::SetUseBestVisual
wxApp::Yield

### wxApp::wxApp

void wxApp()

Constructor. Called implicitly with a definition of a wxApp object.

### wxApp::~wxApp

void ~wxApp()

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

### wxApp::argc

int argc

Number of command line arguments (after environment-specific processing).

### wxApp::argv

char ** argv

Command line arguments (after environment-specific processing).

### wxApp::CreateLogTarget

virtual wxLog* CreateLogTarget()

Creates a wxLog class for the application to use for logging errors. The default implementation returns a new wxLogGui class.

See also

wxLog

### wxApp::Dispatch

void Dispatch()

Dispatches the next event in the windowing system event queue.

This can be used for programming event loops, e.g.

      while (app.Pending())
        Dispatch();

See also

wxApp::Pending

### wxApp::FilterEvent

int FilterEvent(wxEvent& event)

This function is called before processing any event and allows the application to preempt the processing of some events. If this method returns -1 the event is processed normally, otherwise either `TRUE` or `FALSE` should be returned and the event processing stops immediately considering that the event had been already processed (for the former return value) or that it is not going to be processed at all (for the latter one).

### wxApp::GetAppName

wxString GetAppName() const

Returns the application name.

Remarks

wxWindows sets this to a reasonable default before calling wxApp::OnInit, but the application can reset it at will.

### wxApp::GetAuto3D

bool GetAuto3D() const

Returns TRUE if 3D control mode is on, FALSE otherwise.

See also

wxApp::SetAuto3D

### wxApp::GetClassName

wxString GetClassName() const

Gets the class name of the application. The class name may be used in a platform specific manner to refer to the application.

See also

wxApp::SetClassName

### wxApp::GetExitOnFrameDelete

bool GetExitFrameOnDelete() const

Returns TRUE if the application will exit when the top-level window is deleted, FALSE otherwise.

See also

wxApp::SetExitOnFrameDelete,
wxApp shutdown overview

### wxApp::GetTopWindow

virtual wxWindow * GetTopWindow() const

Returns a pointer to the top window.

Remarks

If the top window hasn't been set using wxApp::SetTopWindow, this function will find the first top-level window (frame or dialog) and return that.

See also

SetTopWindow

### wxApp::GetUseBestVisual

bool GetUseBestVisual() const

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

See also

SetUseBestVisual

### wxApp::GetVendorName

wxString GetVendorName() const

Returns the application's vendor name.

### wxApp::ExitMainLoop

void ExitMainLoop()

Call this to explicitly exit the main message (event) loop. You should normally exit the main loop (and the application) by deleting the top window.

### wxApp::Initialized

bool Initialized()

Returns TRUE if the application has been initialized (i.e. if wxApp::OnInit has returned successfully). This can be useful for error message routines to determine which method of output is best for the current state of the program (some windowing systems may not like dialogs to pop up before the main loop has been entered).

### wxApp::MainLoop

int MainLoop()

Called by wxWindows on creation of the application. Override this if you wish to provide your own (environment-dependent) main loop.

Return value

Returns 0 under X, and the wParam of the WM_QUIT message under Windows.

### wxApp::OnAssert

void OnAssert(const wxChar *file, int line, 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`. It is only called in debug mode (when `__WXDEBUG__` is defined) as asserts are not left in the release code at all.

The base class version show the default assert failure dialog box proposing to the user to stop the program, continue or ignore all subsequent asserts.

Parameters

file

the name of the source file where the assert occured

line

the line number in this file where the assert occured

cond

the condition of the failed assert in string form

msg

the message specified as argument to wxASSERT_MSG or wxFAIL_MSG, will be `NULL` if just wxASSERT or wxFAIL was used

### wxApp::OnExit

int OnExit()

Provide this member function for any processing which needs to be done as the application is about to exit. OnExit is called after destroying all application windows and controls, but before wxWindows cleanup.

### wxApp::OnCmdLineError

bool OnCmdLineError(wxCmdLineParser& parser)

Called when command line parsing fails (i.e. an incorrect command line option was specified by the user). The default behaviour is to show the program usage text and abort the program.

Return `TRUE` to continue normal execution or `FALSE` to return `FALSE` from OnInit thus terminating the program.

See also

OnInitCmdLine

### wxApp::OnCmdLineHelp

bool OnCmdLineHelp(wxCmdLineParser& parser)

Called when the help option (`--help`) was specified on the command line. The default behaviour is to show the program usage text and abort the program.

Return `TRUE` to continue normal execution or `FALSE` to return `FALSE` from OnInit thus terminating the program.

See also

OnInitCmdLine

### wxApp::OnCmdLineParsed

bool OnCmdLineParsed(wxCmdLineParser& parser)

Called after the command line had been successfully parsed. You may override this method to test for the values of the various parameters which could be set from the command line.

Don't forget to call the base class version unless you want to suppress processing of the standard command line options.

Return `TRUE` to continue normal execution or `FALSE` to return `FALSE` from OnInit thus terminating the program.

See also

OnInitCmdLine

### wxApp::OnFatalException

void OnFatalException()

This function may be called if something fatal happens: an unhandled exception under Win32 or a a fatal signal under Unix, for example. However, this will not happen by default: you have to explicitly call wxHandleFatalExceptions to enable this.

Generally speaking, this function should only show a message to the user and return. You may attempt to save unsaved data but this is not guaranteed to work and, in fact, probably won't.

See also

wxHandleFatalExcetions

### wxApp::OnInit

bool OnInit()

This must be provided by the application, and will usually create the application's main window, optionally calling wxApp::SetTopWindow.

Notice that if you want to to use the command line processing provided by wxWindows you have to call the base class version in the derived class OnInit().

Return TRUE to continue processing, FALSE to exit the application.

### wxApp::OnInitCmdLine

void OnInitCmdLine(wxCmdLineParser& parser)

Called from OnInit and may be used to initialize the parser with the command line options for this application. The base class versions adds support for a few standard options only.

### wxApp::OnQueryEndSession

void OnQueryEndSession(wxCloseEvent& event)

This is an event handler function called when the operating system or GUI session is about to close down. Typically, an application will try to save unsaved documents at this point.

If wxCloseEvent::CanVeto returns TRUE, the application is allowed to veto the shutdown by calling wxCloseEvent::Veto. The application might veto the shutdown after prompting for documents to be saved, and the user has cancelled the save.

Use the EVT_QUERY_END_SESSION event table macro to handle query end session events.

You should check whether the application is forcing the deletion of the window using wxCloseEvent::GetForce. If this is TRUE, destroy the window using wxWindow::Destroy. If not, it is up to you whether you respond by destroying the window.

The default handler calls wxWindow::Close on the top-level window, and vetoes the shutdown if Close returns FALSE. This will be sufficient for many applications.

Remarks

Under X, OnQueryEndSession is called in response to the 'save session' event.

Under Windows, OnQueryEndSession is called in response to the WM_QUERYENDSESSION message.

See also

wxWindow::Close, wxCloseEvent

### wxApp::ProcessMessage

bool 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 wxWindows with another class library with its own message loop, you should make sure that this function is called to allow wxWindows to receive messages. For example, to allow co-existence with the Microsoft Foundation Classes, override the PreTranslateMessage function:

    // Provide wxWindows message loop compatibility
    BOOL CTheApp::PreTranslateMessage(MSG *msg)
    {
      if (wxTheApp && wxTheApp->ProcessMessage((WXMSW *)msg))
        return TRUE;
      else
        return CWinApp::PreTranslateMessage(msg);
    }

### wxApp::Pending

bool Pending()

Returns TRUE if unprocessed events are in the window system event queue.

See also

wxApp::Dispatch

### wxApp::SendIdleEvents

bool SendIdleEvents()

Sends idle events to all top-level windows.

bool SendIdleEvents(wxWindow* win)

Sends idle events to a window and its children.

Remarks

These functions poll the top-level windows, and their children, for idle event processing. If TRUE is returned, more OnIdle processing is requested by one or more window.

See also

wxIdleEvent

### wxApp::SetAppName

void SetAppName(const wxString& name)

Sets the name of the application. The name may be used in dialogs (for example by the document/view framework). A default name is set by wxWindows.

See also

wxApp::GetAppName

### wxApp::SetAuto3D

void SetAuto3D(const bool auto3D)

Switches automatic 3D controls on or off.

Parameters

auto3D

If TRUE, all controls will be created with 3D appearances unless overridden for a control or dialog. The default is TRUE

Remarks

This has an effect on Windows only.

See also

wxApp::GetAuto3D

### wxApp::SetClassName

void SetClassName(const wxString& name)

Sets the class name of the application. This may be used in a platform specific manner to refer to the application.

See also

wxApp::GetClassName

### wxApp::SetExitOnFrameDelete

void SetExitOnFrameDelete(bool flag)

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

Parameters

flag

If TRUE (the default), the application will exit when the top-level frame is deleted. If FALSE, the application will continue to run.

See also

wxApp::GetExitOnFrameDelete,
wxApp shutdown overview

### wxApp::SetTopWindow

void SetTopWindow(wxWindow* window)

Sets the 'top' window. You can call this from within wxApp::OnInit to let wxWindows 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, wxWindows just uses the first frame or dialog in its top-level window list, when it needs to use the top window.

Parameters

window

The new top window.

See also

wxApp::GetTopWindow, wxApp::OnInit

### wxApp::SetVendorName

void SetVendorName(const wxString& name)

Sets the name of application's vendor. The name will be used in registry access. A default name is set by wxWindows.

See also

wxApp::GetVendorName

### wxApp::SetUseBestVisual

void SetUseBestVisual(bool flag)

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

flag

If TRUE, the app will use the best visual.

### wxApp::Yield

bool Yield(bool onlyIfNeeded = FALSE)

Yields control to pending messages in the windowing system. This can be useful, for example, when a time-consuming process writes to a text window. Without an occasional yield, the text window will not be updated properly, and on systems with cooperative multitasking, such as Windows 3.1 other processes will not respond.

Caution should be exercised, however, since yielding may allow the user to perform actions which are not compatible with the current task. Disabling menu items or whole menus during processing can avoid unwanted reentrance of code: see ::wxSafeYield for a better function.

Note that Yield() will not flush the message logs. This is intentional as calling Yield() is usually done to quickly update the screen and popping up a message box dialog may be undesirable. If you do wish to flush the log messages immediately (otherwise it will be done during the next idle loop iteration), call wxLog::FlushActive.

Calling Yield() recursively is normally an error and an assert failure is raised in debug build if such situation is detected. However if the the onlyIfNeeded parameter is `TRUE`, the method will just silently return `FALSE` instead.