SetReadCallback

Description

Sets up a callback function which will be called when a client application issues a feature read request.

[C++]
int SetReadCallback(void* context, FeatureCallback callback);

   where FeatureCallback type is defined as

    typedef bool (*FeatureCallback)(void* context, const char* feature);


Parameters [C/C++]

[in] void* context

Address of the context in which the callback function will be called.

[in] FeatureCallback callback

Address of the callback function

[in] const char* feature

String containing the name of the feature whose value is about to be read by a client application.

Return Values

S_OK

Success

E_FAIL

Failure

Example

This fragment of an MFC code uses a feature-read callback to obtain the current temperature value from a thermal sensor and modify the value of the Temperature feature before it gets transmitted to the client application.

   int onFeatureRead(void* context, const char* feature)
      {
         CGigemuDlg* dlg = (CGigemuDlg*) context;
         return dlg->onFeatureRead(feature);
      }

int CGigemuDlg::onFeatureRead(const char* feature)

{

if(CString(feature)=="Temperature")

{

float temp;

GetTemperatureFromSensor(&temp);

m_pCamera->SetFeatureFloatValue(feature, temp);

}

return 0;

}

      BOOL CGigemuDlg::OnInitDialog()
      {

....

m_pCamera->SetReadCallback(this, &::onFeatureRead);

....

}

Remarks

The read callback function is called before the value of the feature is transmitted to the client application. Therefore, the callback can be used to update the value of the feature at the time of the read request. This is especially useful when the feature represents a real-world measurement such as the temperature, as shown in the example above.

If you are using a callback function in the main thread of the simulation application, make sure that no lengthy processing is done in the body of the function as otherwise the connection to the remote client may become broken.