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The GC (graphical context) routines are closely related to the Window Private routines, but are accessed through the nfbGCOps(D4nfb) structure. These routines allow your hardware to get a little closer to some of the more heavily-used X graphics primitives. The gen directory contains samples of all these routines.
Four nfbGCOps structures are declared in the xxxData.c file, although not all these routines are used in the current release.
NFB GC context operations
| Fill style | GC components | Operations |
| Solid |
alu
planemask fgPixel |
FillRects(D3nfb)
FillSpans(D3nfb) ZeroSegs(D3nfb) FillPolygons(D3nfb) |
| Stippled |
alu
planemask fgPixel stipple pagOrg |
FillRects(D3nfb)
FillSpans(D3nfb) |
| Opaque stippled |
alu
planemask fgPixel bgPixel stipple pagOrg |
FillRects(D3nfb)
FillSpans(D3nfb) |
| Tiled |
alu
planemask tile pagOrg |
FillRects(D3nfb)
FillSpans(D3nfb) |
By having a stub pointer in the routines, the X server can provide generic routines which your existing device driver can use in place of these stubs. This means that a display driver that uses these routines will automatically take advantage of new routines provided in future releases without being rewritten or recompiled.
If you are developing on a SVR5 system, look at the nteGC.c example. You'll see that the ValidateWindowGC(D3nfb) routine switches in the appropriate routine according to what changes have taken place in the GC. You should not need to optimize this code unless you need to optimize beyond the NFB interface.