A number of regular ObjectWindows classes implement specialized exception classes, all of which are based on TXOwl that are defined within the implementing class definition to provide name scoping.

The following table describes these classes, along with the unique functionality of each class.

Exception Class	Description
TXInvalidMainWindow	Initializes the exception message with the IDS_INVALIDMAINWINDOW string resource. This object is thrown when the MainWindow member of TApplication contains either an invalid pointer or a pointer to an invalid window.
TXInvalidModule	Initializes the exception message with the IDS_INVALIDMODULE string resource. This exception is thrown in the TModule constructor when the module's HInstance is invalid.
TXWindow	Initializes the exception message with the window title and with a string resource passed to the TXWindow constructor. This exception is thrown in situations where an error relating to a window object has occurred.
TXMenu	Initializes the exception message with a string resource passed to the TXMenu constructor, by default, the IDS_GDIFAILURE string resource. This exception is thrown when a menu object's handle is invalid.
TXValidator	Initializes the exception message with a string resource passed to the TXValidator constructor. By default this is the IDS_VALIDATORSYNTAX string resource. This exception is thrown when a validator expression is corrupt or invalid.
TXGdi	Initializes the exception message with a string resource passed to the TXGdi constructor, along with the GDI object handle. By default, the string resource is IDS_GDIFAILURE and the GDI object handle is 0 (zero). This exception is thrown in many situations when an error relating to a graphics object has occurred.
TXPrinter	Initializes the exception message with a string resource passed to the TXPrinter constructor. By default this is the IDS_PRINTERERROR string resource. This exception is thrown when the printer's device context is invalid.
TXBadFormat	Initializes the exception message with the IDS_BADFILEFORMAT string resource. This exception is thrown when an illegal file format is encountered.