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CentOS 7.0 - man page for xdrawarc (centos section 3)

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XDrawArc(3)				  XLIB FUNCTIONS			      XDrawArc(3)

NAME
       XDrawArc, XDrawArcs, XArc - draw arcs and arc structure

SYNTAX
       int XDrawArc(Display *display, Drawable d, GC gc, int x, int y, unsigned int width,
	      unsigned int height, int angle1, int angle2);

       int XDrawArcs(Display *display, Drawable d, GC gc, XArc *arcs, int narcs);

ARGUMENTS
       angle1	 Specifies the start of the arc relative to the three-o'clock position from the
		 center, in units of degrees * 64.

       angle2	 Specifies the path and extent of the arc relative to the start of the arc, in
		 units of degrees * 64.

       arcs	 Specifies an array of arcs.

       d	 Specifies the drawable.

       display	 Specifies the connection to the X server.

       gc	 Specifies the GC.

       narcs	 Specifies the number of arcs in the array.

       width
       height	 Specify the width and height, which are the major and minor axes of the arc.

       x
       y	 Specify the x and y coordinates, which are relative to the origin of the draw-
		 able and specify the upper-left corner of the bounding rectangle.

DESCRIPTION
       XDrawArc draws a single circular or elliptical arc, and XDrawArcs draws multiple circular
       or elliptical arcs.  Each arc is specified by a rectangle and two angles.  The center of
       the circle or ellipse is the center of the rectangle, and the major and minor axes are
       specified by the width and height.  Positive angles indicate counterclockwise motion, and
       negative angles indicate clockwise motion.  If the magnitude of angle2 is greater than 360
       degrees, XDrawArc or XDrawArcs truncates it to 360 degrees.

       For an arc specified as [x,y,width,height,angle1,angle2], the origin of the major and
       minor axes is at [x+_____,y+______], and the infinitely thin path describing the entire
       circle or ellipse intersects the horizontal axis at [x,y+______] and [x+width,y+______]
       and intersects the vertical axis at [x+_____,y] and [x+_____,y+height].	These coordinates
       can be fractional and so are not truncated to discrete coordinates.  The path should be
       defined by the ideal mathematical path.	For a wide line with line-width lw, the bounding
       outlines for filling are given by the two infinitely thin paths consisting of all points
       whose perpendicular distance from the path of the circle/ellipse is equal to lw/2 (which
       may be a fractional value).  The cap-style and join-style are applied the same as for a
       line corresponding to the tangent of the circle/ellipse at the endpoint.

       For an arc specified as [x,y,width,height,angle1,angle2], the angles must be specified in
       the effectively skewed coordinate system of the ellipse (for a circle, the angles and
       coordinate systems are identical).  The relationship between these angles and angles
       expressed in the normal coordinate system of the screen (as measured with a protractor) is
       as follows:

       skewed-angle=atan(tan(normal-angle)*______)+adjust

       The skewed-angle and normal-angle are expressed in radians (rather than in degrees scaled
       by 64) in the range [0,2n] and where atan returns a value in the range [-_,_] and adjust
       is:

       l l.  0	  for normal-angle in the range [0,_] n    for normal-angle in the range [_,__]
       2n   for normal-angle in the range [__,2n]

       For any given arc, XDrawArc and XDrawArcs do not draw a pixel more than once.  If two arcs
       join correctly and if the line-width is greater than zero and the arcs intersect, XDrawArc
       and XDrawArcs do not draw a pixel more than once.  Otherwise, the intersecting pixels of
       intersecting arcs are drawn multiple times.  Specifying an arc with one endpoint and a
       clockwise extent draws the same pixels as specifying the other endpoint and an equivalent
       counterclockwise extent, except as it affects joins.

       If the last point in one arc coincides with the first point in the following arc, the two
       arcs will join correctly.  If the first point in the first arc coincides with the last
       point in the last arc, the two arcs will join correctly.  By specifying one axis to be
       zero, a horizontal or vertical line can be drawn.  Angles are computed based solely on the
       coordinate system and ignore the aspect ratio.

       Both functions use these GC components: function, plane-mask, line-width, line-style, cap-
       style, join-style, fill-style, subwindow-mode, clip-x-origin, clip-y-origin, and clip-
       mask.  They also use these GC mode-dependent components: foreground, background, tile,
       stipple, tile-stipple-x-origin, tile-stipple-y-origin, dash-offset, and dash-list.

       XDrawArc and XDrawArcs can generate BadDrawable, BadGC, and BadMatch errors.

STRUCTURES
       The XArc structure contains:

       typedef struct {
	    short x, y;
	    unsigned short width, height;
	    short angle1, angle2;	      /* Degrees * 64 */
       } XArc;

       All x and y members are signed integers.  The width and height members are 16-bit unsigned
       integers.  You should be careful not to generate coordinates and sizes out of the 16-bit
       ranges, because the protocol only has 16-bit fields for these values.

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

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

       BadMatch  An InputOnly window is used as a Drawable.

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

SEE ALSO
       XDrawLine(3), XDrawPoint(3), XDrawRectangle(3)
       Xlib - C Language X Interface

X Version 11				   libX11 1.6.0 			      XDrawArc(3)
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