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xcreategc(3x11) [ultrix man page]

XCreateGC(3X11) 						     MIT X11R4							   XCreateGC(3X11)

Name
       XCreateGC, XCopyGC, XChangeGC, XGetGCValues, XFreeGC, XGContextFromGC, XGCValues - create or free graphics contexts and graphics context
       structure

Syntax
       GC XCreateGC(display, d, valuemask, values)
	  Display *display;
	  Drawable d;
	  unsigned long valuemask;
	  XGCValues *values;

       XCopyGC(display, src, valuemask, dest)
	  Display *display;
	  GC src, dest;
	  unsigned long valuemask;

       XChangeGC(display, gc, valuemask, values)
	  Display *display;
	  GC gc;
	  unsigned long valuemask;
	  XGCValues *values;

       Status XGetGCValues(display, gc, valuemask, values_return)
	  Display *display;
	  GC gc;
	  unsigned long valuemask;
	  XGCValues *values_return;

       XFreeGC(display, gc)
	  Display *display;
	  GC gc;

       GContext XGContextFromGC(gc)
	  GC gc;

Arguments
       d	 Specifies the drawable.

       dest	 Specifies the destination GC.

       display	 Specifies the connection to the X server.

       gc	 Specifies the GC.

       src	 Specifies the components of the source GC.

       valuemask Specifies which components in the GC are to be set, copied, changed, or returned .  This argument is the bitwise inclusive OR of
		 one or more of the valid GC component mask bits.

       values	 Specifies any values as specified by the valuemask.

       values_return
		 Returns the GC values in the specified structure.

Description
       The function creates a graphics context and returns a GC.  The GC can be used with any destination drawable having the same root and depth
       as the specified drawable.  Use with other drawables results in a error.

       can generate and errors.

       The function copies the specified components from the source GC to the destination GC.  The source and destination GCs must have the same
       root and depth, or a error results.  The valuemask specifies which component to copy, as for

       can generate and errors.

       The function changes the components specified by valuemask for the specified GC.  The values argument contains the values to be set.  The
       values and restrictions are the same as for Changing the clip-mask overrides any previous request on the context.  Changing the dash-offset
       or dash-list overrides any previous request on the context.  The order in which components are verified and altered is server-dependent.
       If an error is generated, a subset of the components may have been altered.

       can generate and errors.

       The function returns the components specified by valuemask for the specified GC.  Note that the clip mask and dash list (represented by the
       and bits, respectively, in the valuemask) cannot be requested.  If the valuemask contains a valid set of GC mask bits or and no error
       occur, sets the requested components in values_return and returns a nonzero status.  Otherwise, it returns a zero status.

       The function destroys the specified GC as well as all the associated storage.

       can generate a error.

Structures
       The structure contains:

       /* GC attribute value mask bits */

       #define				(1L<<0)
       #define				(1L<<1)
       #define				(1L<<2)
       #define				(1L<<3)
       #define				(1L<<4)
       #define				(1L<<5)
       #define				(1L<<6)
       #define				(1L<<7)
       #define				(1L<<8)
       #define				(1L<<9)
       #define				(1L<<10)
       #define				(1L<<11)
       #define				(1L<<12)
       #define				(1L<<13)
       #define				(1L<<14)
       #define				(1L<<15)
       #define				(1L<<16)
       #define				(1L<<17)
       #define				(1L<<18)
       #define				(1L<<19)
       #define				(1L<<20)
       #define				(1L<<21)
       #define				(1L<<22)

       /* Values */

       typedef struct {
	 int function;		    /* logical operation */
	 unsigned long plane_mask;  /* plane mask */
	 unsigned long foreground;  /* foreground pixel */
	 unsigned long background;  /* background pixel */
	 int line_width;	    /* line width (in pixels) */
	 int line_style;	    /* LineSolid, LineOnOffDash,
					LineDoubleDash */
	 int cap_style; 	    /* CapNotLast, CapButt,
					CapRound, CapProjecting */
	 int join_style;	    /* JoinMiter, JoinRound,
					JoinBevel */
	 int fill_style;	    /* FillSolid, FillTiled,
					FillStippled,
					FillOpaqueStippled*/
	 int fill_rule; 	    /* EvenOddRule, WindingRule */
	 int arc_mode;		    /* ArcChord, ArcPieSlice */
	 Pixmap tile;		    /* tile pixmap for tiling
					operations */
	 Pixmap stipple;	    /* stipple 1 plane pixmap for
					stippling */
	 int ts_x_origin;	    /* offset for tile or stipple
					operations */
	 int ts_y_origin;
	 Font font;		    /* default text font for text
					operations */
	 int subwindow_mode;	    /* ClipByChildren,
					IncludeInferiors */
	 Bool graphics_exposures;   /* boolean, should exposures be
					generated */
	 int clip_x_origin;	    /* origin for clipping */
	 int clip_y_origin;
	 Pixmap clip_mask;	    /* bitmap clipping; other calls
					for rects */
	 int dash_offset;	    /* patterned/dashed line
					information */
	 char dashes;
       } XGCValues;

       The function attributes of a GC are used when you update a section of a drawable (the destination) with bits from somewhere else (the
       source).  The function in a GC defines how the new destination bits are to be computed from the source bits and the old destination bits.
       is typically the most useful because it will work on a color display, but special applications may use other functions, particularly in
       concert with particular planes of a color display.  The 16 GC functions, defined in are:

       -----------------------------------------------------
       Function Name	 Hex Code   Operation
       -----------------------------------------------------
       (R)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
       -----------------------------------------------------

       Many graphics operations depend on either pixel values or planes in a GC.  The planes attribute is of type long, and it specifies which
       planes of the destination are to be modified, one bit per plane.  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.

       In graphics operations, given a source and destination pixel, the result is computed bitwise on corresponding bits of the pixels.  That is,
       a Boolean operation is performed in each bit plane.  The plane_mask restricts the operation to a subset of planes.  A macro constant can be
       used to refer to all planes of the screen simultaneously.  The result is computed by the following:

       (R)((src FUNC dst) AND plane-mask) OR (dst AND (NOT plane-mask))

       Range checking is not performed on the values for foreground, background, or plane_mask.  They are simply truncated to the appropriate num-
       ber of bits.  The line-width is measured in pixels and either can be greater than or equal to one (wide line) or can be the special value
       zero (thin line).

       Wide lines are drawn centered on the path described by the graphics request.  Unless otherwise specified by the join-style or cap-style,
       the bounding box of a wide line with endpoints [x1, y1], [x2, y2] and width w is a rectangle with vertices at the following real coordi-
       nates:

       [x1-(w*sn/2), y1+(w*cs/2)], [x1+(w*sn/2), y1-(w*cs/2)],
       [x2-(w*sn/2), y2+(w*cs/2)], [x2+(w*sn/2), y2-(w*cs/2)]

       Here sn is the sine of the angle of the line, and cs is the cosine of the angle of the line.  A pixel is part of the line and so is drawn
       if the center of the pixel is fully inside the bounding box (which is viewed as having infinitely thin edges).  If the center of the pixel
       is exactly on the bounding box, it is part of the line if and only if the interior is immediately to its right (x increasing direction).
       Pixels with centers on a horizontal edge are a special case and are part of the line if and only if the interior or the boundary is immedi-
       ately below (y increasing direction) and the interior or the boundary is immediately to the right (x increasing direction).

       Thin lines (zero line-width) are one-pixel-wide lines drawn using an unspecified, device-dependent algorithm.  There are only two con-
       straints on this algorithm.

       1.   If a line is drawn unclipped from [x1,y1] to [x2,y2] and if another line is drawn unclipped from [x1+dx,y1+dy] to [x2+dx,y2+dy], a
	    point [x,y] is touched by drawing the first line if and only if the point [x+dx,y+dy] is touched by drawing the second line.

       2.   The effective set of points comprising a line cannot be affected by clipping.  That is, a point is touched in a clipped line if and
	    only if the point lies inside the clipping region and the point would be touched by the line when drawn unclipped.

       A wide line drawn from [x1,y1] to [x2,y2] always draws the same pixels as a wide line drawn from [x2,y2] to [x1,y1], not counting cap-style
       and join-style.	It is recommended that this property be true for thin lines, but this is not required.	A line-width of zero may differ
       from a line-width of one in which pixels are drawn.  This permits the use of many manufacturers' line drawing hardware, which may run many
       times faster than the more precisely specified wide lines.

       In general, drawing a thin line will be faster than drawing a wide line of width one.  However, because of their different drawing algo-
       rithms, thin lines may not mix well aesthetically with wide lines.  If it is desirable to obtain precise and uniform results across all
       displays, a client should always use a line-width of one rather than a line-width of zero.

       The line-style defines which sections of a line are drawn:

       LineSolid	The full path of the line is
			drawn.
       LineDoubleDash	The full path of the line is
			drawn, but the even dashes are
			filled differently than the odd
			dashes (see fill-style) with style
			used where even and odd dashes
			meet.
       LineOnOffDash	Only the even dashes are drawn,
			and cap-style applies to all
			internal ends of the individual
			dashes, except is treated as

       The cap-style defines how the endpoints of a path are drawn:

       CapNotLast      This is equivalent to except that
		       for a line-width of zero the final
		       endpoint is not drawn.
       CapButt	       The line is square at the endpoint
		       (perpendicular to the slope of the
		       line) with no projection beyond.
       CapRound        The line has a circular arc with
		       the diameter equal to the line-
		       width, centered on the endpoint.
		       (This is equivalent to for line-
		       width of zero).
       CapProjecting   The line is square at the end, but
		       the path continues beyond the end-
		       point for a distance equal to half
		       the line-width.	(This is equiva-
		       lent to for line-width of zero).

       The join-style defines how corners are drawn for wide lines:

       JoinMiter      The outer edges of two lines
		      extend to meet at an angle.  How-
		      ever, if the angle is less than 11
		      degrees, then a join-style is used
		      instead.
       JoinRound      The corner is a circular arc with
		      the diameter equal to the line-
		      width, centered on the joinpoint.
       JoinBevel      The corner has endpoint styles
		      with the triangular notch filled.

       For a line with coincident endpoints (x1=x2, y1=y2), when the cap-style is applied to both endpoints, the semantics depends on the line-
       width and the cap-style:

       CapNotLast      thin   The results are device-
			      dependent, but the
			      desired effect is that
			      nothing is drawn.
       CapButt	       thin   The results are device-
			      dependent, but the
			      desired effect is that a
			      single pixel is drawn.
       CapRound        thin   The results are the same
			      as for
       CapProjecting   thin   The results are the same
			      as for
       CapButt	       wide   Nothing is drawn.
       CapRound        wide   The closed path is a cir-
			      cle, centered at the end-
			      point, and with the diam-
			      eter equal to the line-
			      width.
       CapProjecting   wide   The closed path is a
			      square, aligned with the
			      coordinate axes, centered
			      at the endpoint, and with
			      the sides equal to the
			      line-width.

       For a line with coincident endpoints (x1=x2, y1=y2), when the join-style is applied at one or both endpoints, the effect is as if the line
       was removed from the overall path.  However, if the total path consists of or is reduced to a single point joined with itself, the effect
       is the same as when the cap-style is applied at both endpoints.

       The tile/stipple and clip origins are interpreted relative to the origin of whatever destination drawable is specified in a graphics
       request.  The tile pixmap must have the same root and depth as the GC, or a error results.  The stipple pixmap must have depth one and must
       have the same root as the GC, or a error results.  For stipple operations where the fill-style is but not the stipple pattern is tiled in a
       single plane and acts as an additional clip mask to be ANDed with the clip-mask.  Although some sizes may be faster to use than others, any
       size pixmap can be used for tiling or stippling.

       The fill-style defines the contents of the source for line, text, and fill requests.  For all text and fill requests (for example, and for
       line requests with line-style (for example, and for the even dashes for line requests with line-style or the following apply:

       FillSolid	    Foreground
       FillTiled	    Tile
       FillOpaqueStippled   A tile with the same width and
			    height as stipple, but with
			    background everywhere stipple
			    has a zero and with foreground
			    everywhere stipple has a one
       FillStippled	    Foreground masked by stipple

       When drawing lines with line-style the odd dashes are controlled by the fill-style in the following manner:

       FillSolid	    Background
       FillTiled	    Same as for even dashes
       FillOpaqueStippled   Same as for even dashes
       FillStippled	    Background masked by stipple

       Storing a pixmap in a GC might or might not result in a copy being made.  If the pixmap is later used as the destination for a graphics
       request, the change might or might not be reflected in the GC.  If the pixmap is used simultaneously in a graphics request both as a desti-
       nation and as a tile or stipple, the results are undefined.

       For optimum performance, you should draw as much as possible with the same GC (without changing its components).  The costs of changing GC
       components relative to using different GCs depend upon the display hardware and the server implementation.  It is quite likely that some
       amount of GC information will be cached in display hardware and that such hardware can only cache a small number of GCs.

       The dashes value is actually a simplified form of the more general patterns that can be set with Specifying a value of N is equivalent to
       specifying the two-element list [N, N] in The value must be nonzero, or a error results.

       The clip-mask restricts writes to the destination drawable.  If the clip-mask is set to a pixmap, it must have depth one and have the same
       root as the GC, or a error results.  If clip-mask is set to the pixels are always drawn regardless of the clip origin.  The clip-mask also
       can be set by calling the or functions.	Only pixels where the clip-mask has a bit set to 1 are drawn.  Pixels are not drawn outside the
       area covered by the clip-mask or where the clip-mask has a bit set to 0.  The clip-mask affects all graphics requests.  The clip-mask does
       not clip sources.  The clip-mask origin is interpreted relative to the origin of whatever destination drawable is specified in a graphics
       request.

       You can set the subwindow-mode to or For both source and destination windows are additionally clipped by all viewable children.	For nei-
       ther source nor destination window is clipped by inferiors.  This will result in including subwindow contents in the source and drawing
       through subwindow boundaries of the destination.  The use of on a window of one depth with mapped inferiors of differing depth is not ille-
       gal, but the semantics are undefined by the core protocol.

       The fill-rule defines what pixels are inside (drawn) for paths given in requests and can be set to or For a point is inside if an infinite
       ray with the point as origin crosses the path an odd number of times.  For a point is inside if an infinite ray with the point as origin
       crosses an unequal number of clockwise and counterclockwise directed path segments.  A clockwise directed path segment is one that crosses
       the ray from left to right as observed from the point.  A counterclockwise segment is one that crosses the ray from right to left as
       observed from the point.  The case where a directed line segment is coincident with the ray is uninteresting because you can simply choose
       a different ray that is not coincident with a segment.

       For both and a point is infinitely small, and the path is an infinitely thin line.  A pixel is inside if the center point of the pixel is
       inside and the center point is not on the boundary.  If the center point is on the boundary, the pixel is inside if and only if the polygon
       interior is immediately to its right (x increasing direction).  Pixels with centers on a horizontal edge are a special case and are inside
       if and only if the polygon interior is immediately below (y increasing direction).

       The arc-mode controls filling in the function and can be set to or For the arcs are pie-slice filled.  For the arcs are chord filled.

       The graphics-exposure flag controls event generation for and requests (and any similar requests defined by extensions).

Diagnostics
       The server failed to allocate the requested resource or server memory.

       A value for a Drawable argument does not name a defined Window or Pixmap.

       A value for a Font or GContext argument does not name a defined Font.

       A value for a GContext argument does not name a defined GContext.

       An	 window is used as a Drawable.

       Some argument or pair of arguments has the correct type and range but fails
		 to match in some other way required by the request.

       A value for a Pixmap argument does not name a defined Pixmap.

       Some numeric value falls outside the range of values accepted by the request.
		 Unless a specific range is specified for an argument, the full range defined by the argument's type is accepted. Any argument
		 defined as a set of alternatives can generate this error.

See Also
       AllPlanes(3X11), XCopyArea(3X11), XCreateRegion(3X11), XDrawArc(3X11), XDrawLine(3X11), XDrawRectangle(3X11), XDrawText(3X11), XFillRectan-
       gle(3X11), XQueryBestSize(3X11), XSetArcMode(3X11), XSetClipOrigin(3X11), XSetFillStyle(3X11), XSetFont(3X11), XSetLineAttributes(3X11),
       XSetState(3X11), XSetTile(3X11)
       X Window System: The Complete Reference, Second Edition, Robert W. Scheifler and James Gettys

																   XCreateGC(3X11)
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