BSD 4_3_Tahoe development

Work on file usr/src/new/X/doc/Xlib/ch06a.t

Synthesized-from: CSRG/cd2/4.3tahoe

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+.NH
+Graphic Output to a Window
+.XS
+Graphic Operations
+.XE
+.NH 2
+Display Functions
+.PP
+.IN "Definitions" "Display Functions"
+.IN "Definitions" "Source"
+.IN "Definitions" "Destination"
+You use display functions when you update  a section of the screen (the
+`destination') with bits from somewhere else (the
+`source').  
+Many procedures below take one of these display functions as an argument.
+The function defines how the new destination bits are to be
+computed from the source bits and the old destination bits.
+\fIGXcopy\fP is typically the most useful as it will work on a color display,
+but special applications may use other functions,
+particularly in concert with particular planes of a color display.
+There are
+.IN "File" "<X/X.h>
+16 such functions, defined in \fI<X/X.h>\fP:
+.KS
+.L
+.TS
+center;
+l c c
+l c l.
+Function Name  Hex Code        Operation
+_
+GXclear        0x0     0
+GXand  0x1     src AND dst
+GXandReverse   0x2     src AND NOT dst
+GXcopy 0x3     src
+GXandInverted  0x4     (NOT src) AND dst
+GXnoop 0x5     dst
+GXxor  0x6     src XOR dst
+GXor   0x7     src OR dst
+GXnor  0x8     (NOT src) AND NOT dst
+GXequiv        0x9     (NOT src) XOR dst
+GXinvert       0xa     NOT dst
+GXorReverse    0xb     src OR NOT dst
+GXcopyInverted 0xc     NOT src
+GXorInverted   0xd     (NOT src) OR dst
+GXnand 0xe     (NOT src) OR NOT dst
+GXset  0xf     1
+.TE
+.PP
+.KE
+.IN "Pixel Values"
+Many of the color functions below take either pixel values or
+\fIplanes\fP as an argument.
+The \fIplanes\fP is an integer which specifies which planes of the
+display are to be modified, one bit per plane.
+.IN "Definitions" "Plane Masks"
+A monochrome display has only one plane and
+will be the least significant bit of the word.
+As planes are added to the display hardware, they will occupy more
+significant bits in the plane mask.
+.PP
+.IN "Macro" "AllPlanes"
+A macro constant \fIAllPlanes\fP can be used to refer to all planes of a display
+simultaneously (``~0'').
+.PP
+.IN "Definitions" "Brush"
+A `brush' is a rectangular area of certain allowable sizes
+which will be painted in the line drawing subroutines at each point
+of the line or curve.
+The upper left corner of the brush follows
+the line or curve.
+The brush is defined by \fIheight\fP and \fIwidth\fP parameters
+to many of the line- and curve-drawing routines.
+.PP
+If the width or height of the brush is greater than one pixel,
+the display hardware
+may paint some pixels more than once.
+It is therefore inadvisable to use
+such brushes with display functions such as \fIGXxor\fP and \fIGXinvert\fP,
+which do
+not have the same effect if applied more than once.