Medical Imaging Interaction Toolkit  2022.04.99-b2814023
Medical Imaging Interaction Toolkit
mitk::CallbackFromGUIThread Class Reference

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 CallbackFromGUIThreadGetInstance ()
 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
... // 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 <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
// 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

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
itk::ReceptorMemberCommand<ThreadedClass>::Pointer command = itk::ReceptorMemberCommand<ThreadedClass>::New();
command->SetCallbackFunction(this, &ThreadedClass::ChangeGUIElementsToIndicateProgress);
// DO NOT delete event now. This will be done by CallThisFromGUIThread after the command will executed.

Definition at line 153 of file mitkCallbackFromGUIThread.h.

Constructor & Destructor Documentation

◆ CallbackFromGUIThread()

mitk::CallbackFromGUIThread::CallbackFromGUIThread ( )

Purposely hidden - singleton.

Member Function Documentation

◆ CallThisFromGUIThread()

void mitk::CallbackFromGUIThread::CallThisFromGUIThread ( itk::Command *  ,
itk::EventObject *  e = nullptr 

Change the current application cursor.

◆ GetInstance()

static CallbackFromGUIThread* mitk::CallbackFromGUIThread::GetInstance ( )

This class is a singleton.

◆ RegisterImplementation()

static void mitk::CallbackFromGUIThread::RegisterImplementation ( CallbackFromGUIThreadImplementation implementation)

To be called by a toolkit specific CallbackFromGUIThreadImplementation.

The documentation for this class was generated from the following file: