Class XbpFileDev() Foundation
Class function of the XbpFileDev class.
Objects of the XbpFileDev() class are exclusively used for the initial creation of a metafile. Metafiles contain graphic information that is created by the Xbase++ GRA engine. Metafiles allow drawings to be saved in a file as a series of graphic primitives and later displayed by "playing back" the metafile. After a metafile has been saved on the hard disk, it can be reloaded and displayed using objects of the XbpMetaFile() class.
An XbpFileDev object represents the device context for a presentation space where graphic output can occur. Rather than displaying the graphic output, it is saved in a metafile. The presentation space is linked with this device context to manage a file as the output device.
Metafiles are normally loaded and displayed using XbpMetaFile objects. In the special case where the metafile does not already exist, the output of graphic functions occurs in main memory and the information is stored by an XbpFileDev object. This object records all calls to graphic functions. After the graphic output in the presentation space is finished, the XbpFileDev object must be detached from the presentation space. The :metaFile() method is called to create the XbpMetaFile object. The object is then ready to save the graphic information in a metafile.
Creating a metafile requires several steps involving objects of the XbpPresSpace(), XbpFileDev() and XbpMetaFile() classes. In the example shown later, user defined functions are used to simplify this process.
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