REF XGraphicsContext                              A.Schoter, August 1991

        COPYRIGHT University of Sussex 1991. All Rights Reserved.

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<<<<<<<<<<<<<<<<<<<<<       X GRAPHIC CONTEXTS    >>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<                             >>>>>>>>>>>>>>>>>>>>>>
<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<<

The procedures  and macros  described  in this  ref file  duplicate  the
equivalent Xlib  C  functions  and  constants  relating  to  controlling
graphic contexts.

         CONTENTS - (Use <ENTER> g to access required sections)

  1   Note

  2   Graphics Functions

  3   Procedures



-------
1  Note
-------

The procedures below are made available by doing:

        uses xlib, XGraphicsContext;

For details see:

                     Xlib - C Language X Interface,
                       MIT X Consortium Standard,
                         X Version 11, Release 4

        Copyright (C) 1985, 1986, 1987, 1988, 1989 Massachusetts
        Institute of Technology,  Cambridge, Massachusetts,  and
        Digital Equipment Corporation, Maynard, Massachusetts.




---------------------
2  Graphics Functions
---------------------

Graphics  functions  are  used  when  a  section  of  the  screen   (the
destination) is updated with bits from elsewhere (the source) to  give a
new image. The exact effect that the  update from the source has on  the
destination is determined by the display function. The following  macros
define the possible display functions.


GXclear                                                          [macro]
        Defines a display function.  Operation is new image  = 0 -  i.e.
        the destination is cleared to the background colour.


GXand                                                            [macro]
        Defines a display function. Operation is new image = source  AND
        destination


GXandReverse                                                     [macro]
        Defines a display function. Operation is new image = source  AND
        NOT(destination).


GXcopy                                                           [macro]
        Defines a display function. Operation is new image = source.


GXandInverted                                                    [macro]
        Defines a display function. Operation is new image = NOT(source)
        AND destination.


GXnoop                                                           [macro]
        Defines a display function. Operation is new image = destination


GXxor                                                            [macro]
        Defines a display function. Operation is new image = source  XOR
        destination.


GXor                                                             [macro]
        Defines a display function. Operation  is new image = source  OR
        destination.


GXnor                                                            [macro]
        Defines a display function. Operation is new image = NOT(source)
        AND NOT(destination).


GXequiv                                                          [macro]
        Defines a display function. Operation is new image = NOT(source)
        XOR destination.


GXinvert                                                         [macro]
        Defines a display function. Operation is NOT(destination).


GXorReverse                                                      [macro]
        Defines a display function. Operation  is new image = source  OR
        NOT(destination).


GXcopyInverted                                                   [macro]
        Defines  a   display   function.  Operation   is   new   image =
        NOT(source).


GXorInverted                                                     [macro]
        Defines a display function. Operation is new image = NOT(source)
        OR destination.


GXnand                                                           [macro]
        Defines a display function. Operation is new image = NOT(source)
        OR NOT(destination).


GXset                                                            [macro]
        Defines a display function.  Operation is new image  = 1 -  i.e.
        the destination is blocked with the foreground colour.




-------------
3  Procedures
-------------

XGContextFrom(GCPtr) -> xid                                  [procedure]
XCreateGC(DspPtr,xid,ulong,XGCValPtr) -> GCPtr               [procedure]
XChangeGC(DspPtr,GCPtr,ulong,XGCValPtr)                      [procedure]
XCopyGC(DspPtr,GCPtr1,ulong,GCPtr2)                          [procedure]
XFreeGC(DspPtr,GCPtr)                                        [procedure]
XSetArcMode(DspPtr,GCPtr,int)                                [procedure]
XSetClipMask(DspPtr,GCPtr,xid)                               [procedure]
XSetClipOrigin(DspPtr,GCPtr,int1,int2)                       [procedure]
XSetClipRectangles(DspPtr,GCPtr,int1,int2,XRectPtr,          [procedure]
            int3,int4)
XSetRegion(DspPtr,GCPtr,region)                              [procedure]
XSetDashes(DspPtr,GCPtr,int1,CharPtr,int2)                   [procedure]
XSetLineAttributes(DspPtr,GCPtr,uint,int1,int2,int3)         [procedure]
XSetFillRule(DspPtr,GCPtr,int)                               [procedure]
XSetFillStyle(DspPtr,GCPtr,int)                              [procedure]
XSetStipple(DspPtr,GCPtr,xid)                                [procedure]
XSetTSOrigin(DspPtr,GCPtr,int1,int2)                         [procedure]
XSetGraphicsExposures(DspPtr,GCPtr,int)                      [procedure]
XSetForeground(DspPtr,GCPtr,ulong)                           [procedure]
XSetBackground(DspPtr,GCPtr,ulong)                           [procedure]
XSetFunction(DspPtr,GCPtr,int)                               [procedure]
XSetPlaneMask(DspPtr,GCPtr,ulong)                            [procedure]
XSetState(DspPtr,GCPtr,ulong1,ulong2,int,ulong3)             [procedure]
XSetSubwindowMode(DspPtr,GCPtr,int)                          [procedure]
XGetGCValues(DspPtr, GCPtr, ulong, XGCValPtr) -> status      [procedure]
        These procedures duplicate the equivalent C functions.




--- C.x/x/pop/ref/XGraphicsContext
--- Copyright University of Sussex 1991. All rights reserved.
