Programming the ActiveX control – PB Docs 2021

You make an ActiveX control do its job by programming it in
scripts, setting its properties, and calling its functions. Depending on
the interface provided by the ActiveX control developer, a single
function call might trigger a whole series of activities or individual
property settings, and function calls may let you control every aspect
of its actions.

An ActiveX control is always active — it does not contain an
object that needs to be opened or activated. The user does not
double-click and start an OLE server. However, you can program the
DoubleClicked or any other event to call a function that starts ActiveX
control processing.

Setting properties in
scripts

Programming an ActiveX control is the same as programming
automation for insertable objects. You use the container’s
Object property to address the properties and functions of the ActiveX
control.

This syntax accesses a property value. You can use it wherever you
use an expression. Its datatype is Any. When the expression is
evaluated, its value has the datatype of the control property:

This syntax calls a function. You can capture its return value in
a variable of the appropriate datatype:

Errors when accessing
properties

The PowerBuilder compiler does not know the correct syntax for
accessing properties and functions of an ActiveX control, so it does not
check any syntax after the Object property. This provides the
flexibility you need to program any ActiveX control. But it also leaves
an application open to runtime errors if the properties and functions
are misnamed or missing.

PowerBuilder provides two events (ExternalException and Error) for
handling OLE errors. If the ActiveX control defines a stock error event,
the PowerBuilder OLE control container has an additional event,
ocx_event. These events allow you to intercept and handle errors without
invoking the SystemError event and terminating the application. You can
also use a TRY-CATCH exception handler.

For more information, see Handling errors.

Using events of the ActiveX
control

An ActiveX control has its own set of events, which PowerBuilder
merges with the events for the custom control container. The ActiveX
control events appear in the Event List view with the PowerBuilder
events. You write scripts for ActiveX control events in PowerScript and
use the Object property to refer to ActiveX control properties and
methods, just as you do for PowerBuilder event scripts.

The only difference between ActiveX control events and
PowerBuilder events is where to find documentation about when the events
get triggered. The ActiveX control provider supplies the documentation
for its events, properties, and functions.

The PowerBuilder Browser provides lists of the properties and
methods of the ActiveX control. For more information, see OLE information in the
Browser.