GPIGuide - Graphics Orders

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GPI Guide and Reference

How to Use the GPI Guide and Reference Graphics Functions Data Types Graphics Orders Graphics Orders Data Types Errors Area and Polygon Primitives Bit Maps Creating and Drawing Retained Graphics Character String Primitives Clipping and Boundary Determination Color and Mix Attributes Correlation Coordinate Spaces and Transformations Editing Retained Graphics and Graphics Segments Fonts Graphics Attributes Line and Arc Primitives Marker Primitives Matrix Multiplication Metafiles Print Job Submission and Manipulation Presentation Spaces and Device Contexts Paths Regions Notices Glossary

This section describes the format of the graphics orders.

Graphics orders are used in the following circumstances:

• Using GpiGetData or GpiPutData functions for bulk transfer of part or all of graphics segment data (unless this is simply being copied without being changed).
• Editing segments with GpiQueryElement and GpiElement.
• Generating metafiles (other than through the Presentation Manager API), or examining their contents. The data part of Graphics Data structured fields within the metafile (see "Metafile Data Format" in the Presentation Manager Programming Reference) consists of graphics orders.

When primitive or attribute functions (plus certain other functions) are specified at the programming interface, and the drawing mode (see GpiSetDrawingMode) is set to drawandretain, graphics orders are constructed and placed in the current graphics segment. One API call often causes a single order to be generated. Sometimes, however, several orders are necessary: an example of this is where a GpiPolyLine call is issued, which specifies more strokes than there is room for, in a single order.

In either case, the order or orders generated by a single API call comprise a single element, unless the application specifically starts an element using the GpiBeginElement function. In this case the element consists of all of the orders generated between this and the following GpiEndElement function. A GpiQueryElement function returns the orders that comprise an element; the application may edit these, and return them to the segment with GpiElement. The Begin Element - End Element orders that surround a multi-order element in the segment are never passed between the application and the system on GpiQueryElement and GpiElement functions. No double word or word alignment can be assumed for orders either within segments or during editing