Okay that sounds good! I try if understand it in the right way:

I call a function in the callback function from the PJSIP (on_incoming_Call);
This function has access to any Widget or to the main window of Qt;
And in this Function I emit a signal;

Have a look at my Pseudo Source Code

uscsippart.cpp: This is the file where the Callbackfunctions of PJSIP are. This callback function is called when someona calls me. And in this function a call another function (incomingCallFunc).

Qt Code: 
  1. /* Callback called by the library upon receiving incoming call */
  2. static void on_incoming_call(pjsua_acc_id acc_id, pjsua_call_id call_id,
  3.                              pjsip_rx_data *rdata)
  4. {
  5.      pjsua_call_info ci;
  6.  
  7.      PJ_UNUSED_ARG(acc_id);
  8.      PJ_UNUSED_ARG(rdata);
  9.  
  10.      pjsua_call_get_info(call_id, &ci);
  11.  
  12.      PJ_LOG(3,(THIS_FILE, "Incoming call from %.*s!!",
  13.                           (int)ci.remote_info.slen,
  14.                           ci.remote_info.ptr));
  15.  
  16.      /* Automatically answer incoming calls with 200/OK */
  17.      pjsua_call_answer(call_id, 200, NULL, NULL);
  18.      incomingCallFunc();
  19. }
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uscinterface.h: here is a "DummyObject" which should has a signal and further here is the prototyp of the function incomingCallFunc();

Qt Code: 
  1. #ifndef INTERFACE_H
  2. #define INTERFACE_H
  3.  
  4. #include <QObject>
  5.  
  6. class IncomingCall : public QObject
  7. {
  8. 	Q_OBJECT
  9.  
  10. 	public:
  11. 		IncomingCall(QObject *parent = 0);
  12.  
  13.  
  14. 	signals:
  15. 		void incomingCallsignal();
  16. };
  17.  
  18. void incomingCallFunc(void);
  19. #endif
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uscinterface.cpp: looks like this!

Qt Code: 
  1. #include "uscinterface.h"
  2.  
  3. IncomingCall::IncomingCall (QObject *parent)
  4. 	: QObject(parent)
  5. {
  6. }
  7.  
  8. void incomingCallFunc()
  9. {
  10. 	// QT Code to emit a signal
  11. }
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uscgui.h:

Qt Code: 
  1. #ifndef USCGUI_H
  2. #define USCGUI_H
  3.  
  4. #include <QWidget>
  5.  
  6. class QLabel;
  8.  
  9. class UscGuiES01 : public QWidget
  10. {
  11. 	Q_OBJECT
  12.  
  13. public:
  14. 	UscGuiES01(QWidget *parent = 0);
  15.  
  16. signals:
  17.  
  18. private slots:
  19.  
  20. 	void makeCall();
  21. 	void incomingCall();
  22. private:
  23. 	QLabel *statusLabel;
  24. 	QPushButton *acceptButton;
  25. 	QPushButton *hangupButton;
  26. 	QPushButton *dialButton;
  27. };
  28.  
  29. class UscStatusDisplay : public QWidget
  30. {
  31. 	Q_OBJECT
  32.  
  33. 	public:
  34. 		UscStatusDisplay(QWidget *parent = 0);
  35. };
  36. #endif
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and now uscgui.cpp: Here I generate my GUI I connect Signals and Slots.

Qt Code: 
  1. #include <pjlib.h>
  2. #include <pjlib-util.h>
  3. #include <pjmedia.h>
  4. #include <pjmedia-codec.h>
  5. #include <pjsip.h>
  6. #include <pjsip_simple.h>
  7. #include <pjsip_ua.h>
  8. #include <pjsua-lib/pjsua.h>
  9.  
  10. #include <QtGui>
  11. #include "uscgui.h"
  12. #include "uscinterface.h"
  13.  
  14. UscGuiES01::UscGuiES01(QWidget *parent)
  15. 	: QWidget(parent)
  16. {
  17.  
  18. 		statusLabel = new QLabel(tr("???"));
  19.  
  20. 		dialButton = new QPushButton(tr("Dial"));
  21.  
  22. 		acceptButton = new QPushButton(tr("Accept"));
  23. 		acceptButton->setDefault(true);
  24. 		acceptButton->setEnabled(false);
  25.  
  26. 		hangupButton = new QPushButton(tr("Hang Up"));
  27. 		hangupButton->setEnabled(false);
  28.  
  29. 		UscStatusDisplay *uscGuiStatusDisplay = new UscStatusDisplay;
  30. 		IncomingCall *incomingCall = new IncomingCall;
  31.  
  32.  
  33. /*
  34.  Insert here the connections for the Signals and Slots
  35.  System
  36. */
  37.  
  38. 		connect(dialButton, SIGNAL(clicked()),
  39. 				this, SLOT(makeCall()));
  40.  
  41. 		connect(incomingCall, SIGNAL(incomingCallsignal()),
  42. 				this, SLOT(incomingCall()));
  43.  
  44. 		QHBoxLayout *bottomLayout = new QHBoxLayout;
  45. 		bottomLayout->addWidget(dialButton);
  46. 		bottomLayout->addWidget(acceptButton);
  47. 		bottomLayout->addWidget(hangupButton);
  48.  
  49. 		QHBoxLayout *topLayout = new QHBoxLayout;
  50. 		topLayout->addWidget(statusLabel);
  51. 		topLayout->addWidget(uscGuiStatusDisplay);
  52.  
  53. 		QVBoxLayout *mainLayout = new QVBoxLayout;
  54. 		mainLayout->addLayout(topLayout);
  55. 		mainLayout->addLayout(bottomLayout);
  56. 		setLayout(mainLayout);
  57.  
  58. 		setWindowTitle(tr("Universal SIP Client"));
  59.  
  60. 		emit 
  61. }
  62. /*
  63.  Insert here the SLOT Functions
  64. */
  65.  
  66. void UscGuiES01::makeCall()
  67. {
  68. 	pj_str_t uri = pj_str("sip:nb100149@10.17.1.17");
  69. 	pjsua_call_make_call(0, &uri, 0, NULL, NULL, NULL);
  70. }
  71.  
  72. void UscGuiES01::incomingCall()
  73. {
  74. 	acceptButton->setEnabled(true);
  75. 	hangupButton->setEnabled(true);
  76. }
  77.  
  78. UscStatusDisplay::UscStatusDisplay(QWidget *parent)
  79. 	: QWidget(parent)
  80. {
  81. 	setPalette(QPalette(QColor(Qt::green)));
  82. 	setAutoFillBackground(true);
  83. }
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Now I want to emit the signal of the class Incomingcall(uscinterface.h) by the function incomingCallFunc() in uscinterface.cpp. but I don't now how??

Or, another possibility, I want to set in this function the Buttons (accept, hangup) enabled and leave the signals and slots out for this part.

So, how can I implement that this function has access to the widget (uscgui.cpp)


I have no idea?

Best Regards...