Member variable XbpColumn():drawMode Foundation

The :drawMode instance variable specifies the mode used to display the XbpColumn object on the screen. In the default draw mode (XBP_DRAW_NORMAL), the operating system takes full control over the drawing process. In this mode, a column object is displayed using default imagery and the object's appearance cannot be controlled by the application. However, this default behaviour can be overriden. If the value XBP_DRAW_OWNER or XBP_DRAW_OWNERADVANCED is assigned to the :drawMode instance variable, no drawing is performed by the operating system. Instead, the Xbase++ runtime system uses xbeP_CustomDrawCell()events to notify the application whenever cells of the XbpColumn object need to be redrawn. The application is responsible for processing this event, and for creating the on-screen visualization. For this, the Graphics Engine commands can be used.

This protocol is called owner-drawing because displaying the column object is the responsibility of the object's owner. Using owner-drawing, an application can customize the visualization and the behaviour of an XbpColumn object.

The drawing mode must be assigned to :drawMode before the method :create() is executed.

Changing the drawing mode of an XbpColumn object also affects the way the various column areas are being drawn. Enabling owner-drawing for an XbpColumn object also enables owner-drawning for the heading, data and footing areas. In owner-drawn columns, all requests for drawing cells are forwarded to the XbpBrowse object which displays the columns. See methods :create() as well as XbpCellGroup:customDrawCell for further information.