About using OLE in DataWindow objects
A DataWindow object can include a control that is a container for
an OLE object. The container stores information about the application
that created the object and it can launch the application to display
or modify the OLE object.
The container can fill the whole DataWindow object, when you create
a new DataWindow object using the OLE presentation style, or it can exist alongside
other controls in a DataWindow object, when you add an OLE object to an
existing DataWindow object. You can also read OLE data from a blob column
in a database and display the objects in the DataWindow object.
You can use OLE objects in DataWindow objects in the following ways:
- OLE object in
a DataWindow object The OLE object is displayed in its container control with
the DataWindow data and other controls, such as bitmaps or text.
You can associate it with data in a particular row, the rows on
a page, or with all rows. You choose which columns in the DataWindow object are
transferred to the OLE object. You can add an OLE container control
to a DataWindow object that uses any presentation style that supports multiple DataWindow objects.
(This does not include the graph and RichText presentation styles.) - OLE presentation style The OLE presentation style is similar to an OLE object in
a DataWindow object. The difference is that the OLE container is the
only control in the DataWindow object. The underlying data is not presented
in column controls and there are no other controls, such
as bitmaps or text. The OLE object is always associated
with all the rows in the DataWindow object. - OLE database blob column OLE objects that are stored in the database in a blob column
are displayed in each row of the DataWindow object.
You can also add ActiveX controls (also called OLE custom
controls or OCXs) to DataWindow objects. ActiveX controls range from simple
visual displays, such as meters and clocks, to more complex controls
that perform spell checking or image processing.
The behavior of OLE objects in DataWindow objects is similar
to the behavior of OLE controls in windows.
For more information about linked and embedded
objects and automation, see the chapter on using OLE in an application
in Application Techniques
.
Activating OLE objects
When you are working in the DataWindow painter, you can start the
server application for an OLE object by selecting Open from the
pop-up menu. Once the server application has started, you can use
the tools provided by the server to edit the initial presentation
of the object.
If the OLE object is associated with all rows retrieved
and is in the foreground or background layer, not the band layer,
users can activate the object. If the object is associated with
a single row or page or is in the band layer, users can see the
object but cannot activate it. DataWindows created using the OLE presentation
style are always associated with all rows.
Unlike OLE objects, ActiveX controls are always active. They
do not contain objects that need to be opened or activated.
Editing OLE objects
When an OLE object is activated, you can edit the presentation
of the data. Changes made to DataWindow data affect the OLE object.
Changes made to the OLE object do not affect
the data the DataWindow object retrieved.
Each OLE object stored in the database in a blob column can
be activated and changed. When the DataWindow object updates the
database, the changes are saved.
What’s next
Whether you are inserting an OLE object into a DataWindow object or
using the OLE presentation style, you use the same procedures to
define, preview, and specify data for the OLE object. Because of
their similarities, the next section discusses both OLE objects
in DataWindow objects and the OLE presentation style. The last section
discusses OLE database blob columns.