Allows threads to call some method from within the GUI thread. More...

#include <mitkCallbackFromGUIThread.h>

Public Member Functions
void	CallThisFromGUIThread (itk::Command , itk::EventObject e=nullptr)
	Change the current application cursor. More...

Static Public Member Functions
static CallbackFromGUIThread *	GetInstance ()
	This class is a singleton. More...

static void	RegisterImplementation (CallbackFromGUIThreadImplementation *implementation)
	To be called by a toolkit specific CallbackFromGUIThreadImplementation. More...

Protected Member Functions
	CallbackFromGUIThread ()
	Purposely hidden - singleton. More...

Detailed Description

Allows threads to call some method from within the GUI thread.

This class is useful for use with GUI toolkits that are not thread-safe, e.g. Qt. Any thread that needs to work with the GUI at some time during its execution (e.g. at the end, to display some results) can use this class to ask for a call to a member function from the GUI thread.

Usage example

We assume that you have a class ThreadedClass, that basically lives in a thread that is different from the GUI thread. Now this class has to change some element of the GUI to indicate its status. This could be dangerous (with Qt it is for sure).

The solution is, that ThreadedClass asks mitk::CallbackFromGUIThread to call a method from the GUI thread (main thread).

Here is part of the header of ThreadedClass:

class ThreadedClass : public ParentClass
{
  public:
    ... // All you need
    // This function runs in its own thread !
    void ThreadedFunction();
    // This should be called from the GUI thread
    void ChangeGUIElementsToIndicateProgress(const itk::EventObject&);
    ...
};

#include "mitkCallbackFromGUIThread.h"
#include <itkCommand.h>
// This method runs in a thread of its own! So it can't manipulate GUI elements directly without causing trouble
void ThreadedClass::ThreadedFunction()
{
  ...
  // Create a command object (passing parameters comes later)
  itk::ReceptorMemberCommand<ThreadedClass>::Pointer command = itk::ReceptorMemberCommand<ThreadedClass>::New();
  command->SetCallbackFunction(this, &ThreadedClass::ChangeGUIElementsToIndicateProgress);
  // Ask to execute that command from the GUI thread
  mitk::CallbackFromGUIThread::GetInstance()->CallThisFromGUIThread(command);
  ...
}
// Do dangerous GUI changing stuff here
void ThreadedClass::ChangeGUIElementsToIndicateProgress(const itk::EventObject& e)
{
  Application::GetButtonGrid()->AddButton("Stop");    // this is pseudo code
}

This obviously won't allow you to pass parameters to ChangeGUIElementsToIndicateProgress. If you need to do that, you have to create a kind of itk::EventObject that can be asked for a parameter (this solution is not nice, if you see a better solution, please mail to mitk-.nosp@m.user.nosp@m.s@lis.nosp@m.ts.s.nosp@m.ource.nosp@m.forg.nosp@m.e.net).

The itk::EventObject has to be created with "new" (which can also be done by calling MakeObject on an existing EventObject).

    const mitk::OneParameterEvent* event = new mitk::OneParameterEvent(1); // this class is not yet defined but will
be
    itk::ReceptorMemberCommand<ThreadedClass>::Pointer command = itk::ReceptorMemberCommand<ThreadedClass>::New();
    command->SetCallbackFunction(this, &ThreadedClass::ChangeGUIElementsToIndicateProgress);
    mitk::CallbackFromGUIThread::GetInstance()->CallThisFromGUIThread(command, event);
    // DO NOT delete event now. This will be done by CallThisFromGUIThread after the command will executed.