339 lines
11 KiB
Objective-C
339 lines
11 KiB
Objective-C
/////////////////////////////////////////////////////////////////////////////
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// Name: wx/evtloop.h
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// Purpose: wxEventLoop and related classes
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// Author: Vadim Zeitlin
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// Copyright: (C) 2008 Vadim Zeitlin
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// Licence: wxWindows licence
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/////////////////////////////////////////////////////////////////////////////
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/**
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@class wxEventLoopBase
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Base class for all event loop implementations.
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An event loop is a class which queries the queue of native events sent
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to the wxWidgets application and dispatches them to the appropriate
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wxEvtHandlers.
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An object of this class is created by wxAppTraits::CreateEventLoop() and
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used by wxApp to run the main application event loop.
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Temporary event loops are usually created by wxDialog::ShowModal().
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You can create your own event loop if you need, provided that you restore
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the main event loop once yours is destroyed (see wxEventLoopActivator).
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Notice that there can be more than one event loop at any given moment, e.g.
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an event handler called from the main loop can show a modal dialog, which
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starts its own loop resulting in two nested loops, with the modal dialog
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being the active one (its IsRunning() returns @true). And a handler for a
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button inside the modal dialog can, of course, create another modal dialog
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with its own event loop and so on. So in general event loops form a stack
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and only the event loop at the top of the stack is considered to be active.
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It is also the only loop that can be directly asked to terminate by calling
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Exit() (which is done by wxDialog::EndModal()), an outer event loop can't
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be stopped while an inner one is still running. It is however possible to
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ask an outer event loop to terminate as soon as all its nested loops exit
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and the control returns back to it by using ScheduleExit().
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@library{wxbase}
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@category{appmanagement}
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@see wxApp, wxEventLoopActivator
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*/
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class wxEventLoopBase
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{
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public:
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/**
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Return the currently active (running) event loop.
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May return @NULL if there is no active event loop (e.g. during
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application startup or shutdown).
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*/
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static wxEventLoopBase *GetActive();
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/**
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Set currently active (running) event loop.
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Called by wxEventLoopActivator, use an instance of this class instead
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of calling this method directly to ensure that the previously active
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event loop is restored.
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Results in a call to wxAppConsole::OnEventLoopEnter.
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*/
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static void SetActive(wxEventLoopBase* loop);
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/**
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Returns @true if this is the main loop executed by wxApp::OnRun().
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*/
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bool IsMain() const;
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/**
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@name Dispatch and processing
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*/
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//@{
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/**
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Start the event loop, return the exit code when it is finished.
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Logically, this method calls Dispatch() in a loop until it returns
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@false and also takes care of generating idle events during each loop
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iteration. However not all implementations of this class really
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implement it like this (e.g. wxGTK does not) so you shouldn't rely on
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Dispatch() being called from inside this function.
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@return The argument passed to Exit() which terminated this event loop.
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*/
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virtual int Run() = 0;
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/**
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Return true if this event loop is currently running.
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Notice that even if this event loop hasn't terminated yet but has just
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spawned a nested (e.g. modal) event loop, this method would return
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@false.
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*/
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bool IsRunning() const;
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/**
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Use this to check whether the event loop was successfully created
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before using it
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*/
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virtual bool IsOk() const;
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/**
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Exit the currently running loop with the given exit code.
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The loop will exit, i.e. its Run() method will return, during the next
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event loop iteration.
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Notice that this method can only be used if this event loop is the
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currently running one, i.e. its IsRunning() returns @true. If this is
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not the case, an assert failure is triggered and nothing is done as
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outer event loops can't be exited from immediately. Use ScheduleExit()
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if you'd like to exit this loop even if it doesn't run currently.
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*/
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virtual void Exit(int rc = 0);
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/**
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Schedule an exit from the loop with the given exit code.
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This method is similar to Exit() but can be called even if this event
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loop is not the currently running one -- and if it is the active loop,
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then it works in exactly the same way as Exit().
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The loop will exit as soon as the control flow returns to it, i.e.
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after any nested loops terminate.
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@since 2.9.5
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*/
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virtual void ScheduleExit(int rc = 0) = 0;
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/**
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Return true if any events are available.
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If this method returns @true, calling Dispatch() will not block.
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*/
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virtual bool Pending() const = 0;
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/**
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Dispatches the next event in the windowing system event queue.
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Blocks until an event appears if there are none currently
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(use Pending() if this is not wanted).
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This can be used for programming event loops, e.g.
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@code
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while (evtloop->Pending())
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evtloop->Dispatch();
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@endcode
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@return @false if the event loop should stop and @true otherwise.
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@see Pending(), wxEventLoopBase
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*/
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virtual bool Dispatch() = 0;
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/**
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Dispatch an event but not wait longer than the specified timeout for
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it.
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If an event is received before the specified @a timeout expires, it is
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processed and the function returns 1 normally or 0 if the event loop
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should quite. Otherwise, i.e. if the timeout expires, the functions
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returns -1 without processing any events.
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@param timeout
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The maximal time to wait for the events in milliseconds.
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@return
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1 if an event was processed, 0 if the event loop should quit or -1
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if the timeout expired.
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*/
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virtual int DispatchTimeout(unsigned long timeout) = 0;
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/**
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Called by wxWidgets to wake up the event loop even if it is currently
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blocked inside Dispatch().
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*/
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virtual void WakeUp() = 0;
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//@}
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/**
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@name Idle handling
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*/
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//@{
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/**
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Makes sure that idle events are sent again.
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*/
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void WakeUpIdle();
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/**
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This virtual function is called when the application becomes idle and
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normally just sends wxIdleEvent to all interested parties.
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It should return @true if more idle events are needed, @false if not.
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*/
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virtual bool ProcessIdle();
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//@}
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/**
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@name Yield-related hooks
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*/
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//@{
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/**
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Returns @true if called from inside Yield() or from inside YieldFor().
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*/
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virtual bool IsYielding() const;
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/**
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Yields control to pending messages in the windowing system.
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This can be useful, for example, when a time-consuming process writes to a
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text window. Without an occasional yield, the text window will not be updated
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properly, and on systems with cooperative multitasking, other processes
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will not respond.
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Caution should be exercised, however, since yielding may allow the
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user to perform actions which are not compatible with the current task.
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Disabling menu items or whole menus during processing can avoid unwanted
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reentrance of code: see ::wxSafeYield for a better function.
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Note that Yield() will not flush the message logs. This is intentional as
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calling Yield() is usually done to quickly update the screen and popping up
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a message box dialog may be undesirable. If you do wish to flush the log
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messages immediately (otherwise it will be done during the next idle loop
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iteration), call wxLog::FlushActive.
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If @a onlyIfNeeded parameter is @true and the flow control is already
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inside Yield(), i.e. IsYielding() returns @true, the method just
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silently returns @false and doesn't do anything.
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*/
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bool Yield(bool onlyIfNeeded = false);
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/**
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Works like Yield() with @e onlyIfNeeded == @true, except that it allows
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the caller to specify a mask of the ::wxEventCategory values which
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indicates which events should be processed and which should instead
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be "delayed" (i.e. processed by the main loop later).
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Note that this is a safer alternative to Yield() since it ensures that
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only the events you're interested to will be processed; i.e. this method
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helps to avoid unwanted reentrancies.
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Note that currently only wxMSW and wxGTK do support selective yield of
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native events coming from the underlying GUI toolkit.
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wxWidgets events posted using wxEvtHandler::AddPendingEvent or
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wxEvtHandler::QueueEvent are instead selectively processed by all ports.
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@see wxEvent::GetEventCategory
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*/
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bool YieldFor(long eventsToProcess);
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/**
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Returns @true if the given event category is allowed inside
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a YieldFor() call (i.e. compares the given category against the
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last mask passed to YieldFor()).
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@see wxEvent::GetEventCategory
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*/
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virtual bool IsEventAllowedInsideYield(wxEventCategory cat) const;
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//@}
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protected:
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/**
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This function is called before the event loop terminates, whether this
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happens normally (because of Exit() call) or abnormally (because of an
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exception thrown from inside the loop).
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The default implementation calls wxAppConsole::OnEventLoopExit.
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*/
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virtual void OnExit();
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};
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/**
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@class wxEventLoopActivator
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Makes an event loop temporarily active.
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This class is used to make the event loop active during its life-time,
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e.g.:
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@code
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class MyEventLoop : public wxEventLoopBase { ... };
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void RunMyLoop()
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{
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MyEventLoop loop;
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wxEventLoopActivator activate(&loop);
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...
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} // the previously active event loop restored here
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@endcode
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@library{wxbase}
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@category{appmanagement}
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@see wxEventLoopBase
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*/
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class wxEventLoopActivator
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{
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public:
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/**
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Makes the loop passed as the parameter currently active.
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This saves the current return value of wxEventLoopBase::GetActive() and
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then calls wxEventLoopBase::SetActive() with the given @a loop.
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*/
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wxEventLoopActivator(wxEventLoopBase *loop);
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/**
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Restores the previously active event loop stored by the constructor.
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*/
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~wxEventLoopActivator();
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};
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/**
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@class wxGUIEventLoop
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A generic implementation of the GUI event loop.
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@library{wxbase}
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@category{appmanagement}
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*/
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class wxGUIEventLoop : public wxEventLoopBase
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{
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public:
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wxGUIEventLoop();
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virtual ~wxGUIEventLoop();
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};
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