VB Error Handling | Extensibility

Extensibility > Graphics Builder Automation Interface > Error Handling

Error Handling

Functions, when called from VB, throw an exception on error. The following table lists the possible HRESULT errors that may be encountered:

C++ define	Hex value	Hex codes in VB	Description
S_OK	0	No exception	Successful execution
E_INVALIDARG	80070057	5	One or more arguments are out of range
E_HANDLE	80070006	80070006	No active object (page or graphical object)
E_POINTER	80004003	80004003	Missing or broken link encountered
E_ABORT	80000007	11F	Enumeration terminated or function manually canceled (for example ProjectUpdate)
E_FAIL	80004005	80004005	Every other error

The following VB code can be used to process the error code:

On Error Resume Next
Err.Clear
GraphicsBuilder.LibObjectName Project, File, Page, Type
If Err.Number <> 0 Then
	Debug.Print "Error occurred in LibObjectName"
End If

Note the following points:

VB sets the Err variable only in the erroneous case. It will not be set to 0 if the function succeeds.
When VB handles an exception, it ignores the functions parameters. Hence when a function like ProjectNext does not succeed, the returned string is undefined and not an empty string.

The functions in the groups Page Functions, Options Functions, Object Drawing and Property Functions, Text Property Functions and the individual functions LibSelectionHooksEnabled, SelectionEventEnabled, BrokenLinkCancelEnabled and Visible are treated as variables in VB.

When calling these functions from C++, you need to use a "put_" or "get_" prefix, for example, "put_Visible(TRUE)", "get_Visible(bValue)" to set or fetch the values, except if the Attribute is read-only. In this case the function is the same in C++; for example, PageName.

To evaluate the correct function name for C++ reference the Type library CTDRAW32.TLB, which can be found in Citect SCADA's BIN directory. You can use Microsoft's Visual Studio Tool OLE / COM Object Viewer (select menu File | View Typelib...) to look at a type library.