Function GraSegOpen() Foundation
Begins the definition of a graphic segment.
GraSegOpen( [<oPS>], [<nMode>], [<nSegmentID>] ) --> nSegmentID
GraSegOpen() returns a numeric value by which the graphic segment is later identified. If the constant GRA_SEG_NIL is used for <nMode>, the return value is always 0.
The function GraSegOpen() begins the definition for a graphic segment. A segment is created using graphic primitives such as GraLine(), GraArc(), GraSpline() or GraStringAt() and must be terminated by the function GraSegClose(). A segment records all graphic primitives which are executed between GraSegOpen() and GraSegClose(). A segment can then be drawn on the screen repeatedly without further calls to the graphic primitives. The drawing of a segment occurs using the function GraSegDraw().
When GraSegOpen() is called, the current attribute settings for graphic primitives are not stored in the new segment. When a segment is to store colors or line attributes, for example, the attributes must be re-defined after the segment is opened.
A graphic segment is similar to a graphic path. But, multiple operations can be performed with a segment while only one can be performed with a path. For many operations, like scaling or rotation, a segment must be identified through its numeric segment ID returned by GraSegOpen().
The functions GraSegOpen() and GraSegClose() cannot be nested. After GraSegOpen(), a call to the function GraSegClose() must occur so that graphic primitives can again be used for normal drawing without being recorded in a segment. In addition, it is not possible to create graphic segments as part of a graphic path (a call to GraSegOpen() within GraPathBegin() ... GraPathEnd() is illegal).
Within a presentation space many segments can exist with the segment ID 0, each segment ID not equal to zero exists only once. The maximum number of segments for a presentation space is limited to 16378 (16kB).
Display modes for graphic segments
The drawing or output of a graphic segment occurs in a presentation space which represents an abstract drawing surface (see XbpPresSpace()). The presentation space defines the display mode for graphic segments via the method :drawMode(). As an alternative, the display mode can be set by the function GraSegDrawMode() (see GraSegDrawMode()). In the default display mode GRA_DM_DRAWANDRETAIN, a graphic segment is already visible when the function GraSegClose() is called.
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