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NAME
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Image, draw, drawop, gendraw, gendrawop, drawreplxy, drawrepl,
replclipr, line, lineop, poly, polyop, fillpoly, fillpolyop, bezier,
bezierop, bezspline, bezsplineop, bezsplinepts, fillbezier, fillbezierop,
fillbezspline, fillbezsplineop, ellipse, ellipseop, fillellipse,
fillellipseop, arc, arcop, fillarc, fillarcop, icossin, icossin2,
border, borderop, string, stringop, stringn,
stringnop, runestring, runestringop, runestringn, runestringnop,
stringbg, stringbgop, stringnbg, stringnbgop, runestringbg, runestringbgop,
runestringnbg, runestringnbgop, _string, ARROW, drawsetdebug –
graphics functions
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SYNOPSIS
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#include <u.h>
#include <libc.h>
#include <draw.h>
typedef
struct Image
{
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Display *display; /* display holding data */
int id; /* id of system−held Image */
Rectangle r; /* rectangle in data area, local coords */
Rectangle clipr; /* clipping region */
ulong chan; /* pixel channel format descriptor */
int depth; /* number of bits per pixel */
int repl; /* flag: data replicates to tile clipr */
Screen *screen; /* 0 if not a window */
Image *next; /* next in list of windows */
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} Image;
typedef enum
{
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/* Porter−Duff compositing operators */
Clear = 0,
SinD = 8,
DinS = 4,
SoutD = 2,
DoutS = 1,
S = SinD|SoutD,
SoverD = SinD|SoutD|DoutS,
SatopD = SinD|DoutS,
SxorD = SoutD|DoutS,
D = DinS|DoutS,
DoverS = DinS|DoutS|SoutD,
DatopS = DinS|SoutD,
DxorS = DoutS|SoutD, /* == SxorD */
Ncomp = 12,
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} Drawop;
void draw(Image *dst, Rectangle r, Image *src,
void drawop(Image *dst, Rectangle r, Image *src,
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Image *mask, Point p, Drawop op)
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void gendraw(Image *dst, Rectangle r, Image *src, Point sp,
void gendrawop(Image *dst, Rectangle r, Image *src, Point sp,
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Image *mask, Point mp, Drawop op)
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int drawreplxy(int min, int max, int x)
Point drawrepl(Rectangle r, Point p)
void replclipr(Image *i, int repl, Rectangle clipr)
void line(Image *dst, Point p0, Point p1, int end0, int end1,
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int radius, Image *src, Point sp)
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void lineop(Image *dst, Point p0, Point p1, int end0, int end1,
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int radius, Image *src, Point sp, Drawop op)
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void poly(Image *dst, Point *p, int np, int end0, int end1,
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int radius, Image *src, Point sp)
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void polyop(Image *dst, Point *p, int np, int end0, int end1,
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int radius, Image *src, Point sp, Drawop op)
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void fillpoly(Image *dst, Point *p, int np, int wind,
void fillpolyop(Image *dst, Point *p, int np, int wind,
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Image *src, Point sp, Drawop op)
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int bezier(Image *dst, Point p0, Point p1, Point p2, Point p3,
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int end0, int end1, int radius, Image *src, Point sp)
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int bezierop(Image *dst, Point p0, Point p1, Point p2, Point p3,
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int end0, int end1, int radius, Image *src, Point sp,
Drawop op)
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int bezspline(Image *dst, Point *pt, int npt, int end0, int end1,
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int radius, Image *src, Point sp)
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int bezsplineop(Image *dst, Point *pt, int npt, int end0, int
end1,
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int radius, Image *src, Point sp, Drawop op)
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int bezsplinepts(Point *pt, int npt, Point **pp)
int fillbezier(Image *dst, Point p0, Point p1, Point p2, Point
p3,
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int w, Image *src, Point sp)
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int fillbezierop(Image *dst, Point p0, Point p1, Point p2, Point
p3,
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int w, Image *src, Point sp, Drawop op)
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int fillbezspline(Image *dst, Point *pt, int npt, int w,
int fillbezsplineop(Image *dst, Point *pt, int npt, int w,
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Image *src, Point sp, Drawop op)
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void ellipse(Image *dst, Point c, int a, int b, int thick,
void ellipseop(Image *dst, Point c, int a, int b, int thick,
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Image *src, Point sp, Drawop op)
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void fillellipse(Image *dst, Point c, int a, int b,
void fillellipseop(Image *dst, Point c, int a, int b,
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Image *src, Point sp, Drawop op)
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void arc(Image *dst, Point c, int a, int b, int thick,
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Image *src, Point sp, int alpha, int phi)
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void arcop(Image *dst, Point c, int a, int b, int thick,
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Image *src, Point sp, int alpha, int phi, Drawop op)
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void fillarc(Image *dst, Point c, int a, int b, Image *src,
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Point sp, int alpha, int phi)
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void fillarcop(Image *dst, Point c, int a, int b, Image *src,
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Point sp, int alpha, int phi, Drawop op)
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int icossin(int deg, int *cosp, int *sinp)
int icossin2(int x, int y, int *cosp, int *sinp)
void border(Image *dst, Rectangle r, int i, Image *color, Point
sp)
void borderop(Image *im, Rectangle r, int i, Image *color, Point
sp,
Point string(Image *dst, Point p, Image *src, Point sp,
Point stringop(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, Drawop op)
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Point stringn(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, int len)
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Point stringnop(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, int len, Drawop op)
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Point runestring(Image *dst, Point p, Image *src, Point sp,
Point runestringop(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, Drawop op)
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Point runestringn(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, int len)
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Point runestringnop(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, int len, Drawop op)
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Point stringbg(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, Image *bg, Point bgp)
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Point stringbgop(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, Image *bg, Point bgp, Drawop op)
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Point stringnbg(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, int len, Image *bg, Point bgp)
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Point stringnbgop(Image *dst, Point p, Image *src, Point sp,
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Font *f, char *s, int len, Image *bg, Point bgp, Drawop op)
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Point runestringbg(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, Image *bg, Point bgp)
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Point runestringbgop(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, Image *bg, Point bgp, Drawop op)
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Point runestringnbg(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, int len, Image *bg, Point bgp)
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Point runestringnbgop(Image *dst, Point p, Image *src, Point sp,
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Font *f, Rune *r, int len, Image *bg, Point bgp, Drawop op)
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Point _string(Image *dst, Point p, Image *src,
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Point sp, Font *f, char *s, Rune *r, int len,
Rectangle clipr, Image *bg, Point bgp, Drawop op)
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void drawsetdebug(int on)
enum
{
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/* line ends */
Endsquare = 0,
Enddisc = 1,
Endarrow = 2,
Endmask = 0x1F
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};
#define ARROW(a, b, c) (Endarrow|((a)<<5)|((b)<<14)|((c)<<23))
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DESCRIPTION
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The Image type defines rectangular pictures and the methods to
draw upon them; it is also the building block for higher level
objects such as windows and fonts. In particular, a window is
represented as an Image; no special operators are needed to draw
on a window.
r The coordinates of the rectangle in the plane for which the Image
has defined pixel values. It should not be modified after the
image is created.
clipr The clipping rectangle: operations that read or write the
image will not access pixels outside clipr. Frequently, clipr
is the same as r, but it may differ; see in particular the discussion
of repl. The clipping region may be modified dynamically using
replclipr (q.v.).
chan The pixel channel format descriptor, as described in image(7).
The value should not be modified after the image is created.
depth The number of bits per pixel in the picture; it is identically
chantodepth(chan) (see graphics(3)) and is provided as a convenience.
The value should not be modified after the image is created.
repl A boolean value specifying whether the image is tiled to cover
the plane when used as a source for a drawing operation. If repl
is zero, operations are restricted to the intersection of r and
clipr. If repl is set, r defines the tile to be replicated and
clipr defines the portion of the plane covered by the tiling,
in other words, r is replicated
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to cover clipr; in such cases r and clipr are independent.
For example, a replicated image with r set to ((0, 0), (1, 1))
and clipr set to ((0, 0), (100, 100)), with the single pixel of
r set to blue, behaves identically to an image with r and clipr
both set to ((0, 0), (100, 100)) and all pixels set to blue. However,
the first image requires far less memory. The replication flag
may be modified dynamically
using replclipr (q.v.).
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Most of the drawing functions come in two forms: a basic form,
and an extended form that takes an extra Drawop to specify a Porter-Duff
compositing operator to use. The basic forms assume the operator
is SoverD, which suffices for the vast majority of applications.
The extended forms are named by adding an -op suffix to the basic
form. Only the
basic forms are listed below.
draw(dst, r, src, mask, p)
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Draw is the standard drawing function. Only those pixels within
the intersection of dst−>r and dst−>clipr will be affected; draw
ignores dst−>repl. The operation proceeds as follows (this is a
description of the behavior, not the implementation):
1. If repl is set in src or mask, replicate their contents to fill
their clip rectangles.
2. Translate src and mask so p is aligned with r.min.
3. Set r to the intersection of r and dst−>r.
4. Intersect r with src−>clipr. If src−>repl is false, also intersect
r with src−>r.
5. Intersect r with mask−>clipr. If mask−>repl is false, also intersect
r with mask−>r.
6. For each location in r, combine the dst pixel with the src pixel
using the alpha value corresponding to the mask pixel. If the
mask has an explicit alpha channel, the alpha value corresponding
to the mask pixel is simply that pixel’s alpha channel. Otherwise,
the alpha value is the NTSC greyscale equivalent of the color
value, with white
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meaning opaque and black transparent. In terms of the Porter-Duff
compositing algebra, draw replaces the dst pixels with (src in
mask) over dst. (In the extended form, “over” is replaced by op).
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The various pixel channel formats involved need not be identical.
If the channels involved are smaller than 8-bits, they will be
promoted before the calculation by replicating the extant bits;
after the calculation, they will be truncated to their proper
sizes.
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gendraw(dst, r, src, p0, mask, p1)
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Similar to draw except that gendraw aligns the source and mask
differently: src is aligned so p0 corresponds to r.min and mask
is aligned so p1 corresponds to r.min. For most purposes with
simple masks and source images, draw is sufficient, but gendraw
is the general operator and the one all other drawing primitives
are built upon.
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drawreplxy(min,max,x)
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Clips x to be in the half-open interval [min, max) by adding or
subtracting a multiple of max-min.
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drawrepl(r,p)
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Clips the point p to be within the rectangle r by translating
the point horizontally by an integer multiple of rectangle width
and vertically by the height.
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replclipr(i,repl,clipr)
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Because the image data is stored on the server, local modifications
to the Image data structure itself will have no effect. Repclipr
modifies the local Image data structure’s repl and clipr fields,
and notifies the server of their modification.
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line(dst, p0, p1, end0, end1, thick, src, sp)
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Line draws in dst a line of width 1+2*thick pixels joining points
p0 and p1. The line is drawn using pixels from the src image aligned
so sp in the source corresponds to p0 in the destination. The
line touches both p0 and p1, and end0 and end1 specify how the
ends of the line are drawn. Endsquare terminates the line perpendicularly
to the
direction of the line; a thick line with Endsquare on both ends
will be a rectangle. Enddisc terminates the line by drawing a
disc of diameter 1+2*thick centered on the end point. Endarrow
terminates the line with an arrowhead whose tip touches the endpoint.
The macro ARROW permits explicit control of the shape of the arrow.
If all three parameters are zero, it produces the default arrowhead,
otherwise, a sets the distance along line from end of the regular
line to tip, b sets the distance along line from the barb to the
tip, and c sets the distance perpendicular to the line from edge
of line to the tip of the
barb, all in pixels.
Line and the other geometrical operators are equivalent to calls
to gendraw using a mask produced by the geometric procedure.
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poly(dst, p, np, end0, end1, thick, src, sp)
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Poly draws a general polygon; it is conceptually equivalent to
a series of calls to line joining adjacent points in the array
of Points p, which has np elements. The ends of the polygon are
specified as in line; interior lines are terminated with Enddisc
to make smooth joins. The source is aligned so sp corresponds
to p[0].
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fillpoly(dst, p, np, wind, src, sp)
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Fillpoly is like poly but fills in the resulting polygon rather
than outlining it. The source is aligned so sp corresponds to
p[0]. The winding rule parameter wind resolves ambiguities about
what to fill if the polygon is self-intersecting. If wind is ~0,
a pixel is inside the polygon if the polygon’s winding number
about the point is non-zero. If wind is 1,
a pixel is inside if the winding number is odd. Complementary
values (0 or ~1) cause outside pixels to be filled. The meaning
of other values is undefined. The polygon is closed with a line
if necessary.
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bezier(dst, a, b, c, d, end0, end1, thick, src, sp)
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Bezier draws the cubic Bezier curve defined by Points a, b, c,
and d. The end styles are determined by end0 and end1; the thickness
of the curve is 1+2*thick. The source is aligned so sp in src
corresponds to a in dst.
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bezspline(dst, p, end0, end1, thick, src, sp)
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Bezspline takes the same arguments as poly but draws a quadratic
B-spline (despite its name) rather than a polygon. If the first
and last points in p are equal, the spline has periodic end conditions.
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bezsplinepts(pt, npt, pp)
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Bezsplinepts returns in pp a list of points making up the open
polygon that bezspline would draw. The caller is responsible for
freeing *pp.
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fillbezier(dst, a, b, c, d, wind, src, sp)
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Fillbezier is to bezier as fillpoly is to poly.
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fillbezspline(dst, p, wind, src, sp)
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Fillbezspline is like fillpoly but fills the quadratic B-spline
rather than the polygon outlined by p. The spline is closed with
a line if necessary.
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ellipse(dst, c, a, b, thick, src, sp)
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Ellipse draws in dst an ellipse centered on c with horizontal
and vertical semiaxes a and b. The source is aligned so sp in
src corresponds to c in dst. The ellipse is drawn with thickness
1+2*thick.
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fillellipse(dst, c, a, b, src, sp)
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Fillellipse is like ellipse but fills the ellipse rather than
outlining it.
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arc(dst, c, a, b, thick, src, sp, alpha, phi)
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Arc is like ellipse, but draws only that portion of the ellipse
starting at angle alpha and extending through an angle of phi.
The angles are measured in degrees counterclockwise from the positive
x axis.
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fillarc(dst, c, a, b, src, sp, alpha, phi)
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Fillarc is like arc, but fills the sector with the source color.
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icossin(deg, cosp, sinp)
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Icossin stores in *cosp and *sinp scaled integers representing
the cosine and sine of the angle deg, measured in integer degrees.
The values are scaled so cos(0) is 1024.
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icossin2(x, y, cosp, sinp)
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Icossin2 is analogous to icossin, with the angle represented not
in degrees but implicitly by the point (x,y). It is to icossin
what atan2 is to atan (see sin(3)).
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border(dst, r, i, color, sp)
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Border draws an outline of rectangle r in the specified color.
The outline has width i; if positive, the border goes inside the
rectangle; negative, outside. The source is aligned so sp corresponds
to r.min.
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string(dst, p, src, sp, font, s)
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String draws in dst characters specified by the string s and font;
it is equivalent to a series of calls to gendraw using source
src and masks determined by the character shapes. The text is
positioned with the left of the first character at p.x and the
top of the line of text at p.y. The source is positioned so sp
in src corresponds to p in dst. String
returns a Point that is the position of the next character that
would be drawn if the string were longer.
For characters with undefined or zero-width images in the font,
the character at font position 0 (NUL) is drawn.
The other string routines are variants of this basic form, and
have names that encode their variant behavior. Routines whose
names contain rune accept a string of Runes rather than UTF-encoded
bytes. Routines ending in n accept an argument, n, that defines
the number of characters to draw rather than accepting a NUL-terminated
string.
Routines containing bg draw the background behind the characters
in the specified color (bg) and alignment (bgp); normally the
text is drawn leaving the background intact.
The routine _string captures all this behavior into a single operator.
Whether it draws a UTF string or Rune string depends on whether
s or r is null (the string length is always determined by len).
If bg is non-null, it is used as a background color. The clipr
argument allows further management of clipping when drawing the
string; it is intersected
with the usual clipping rectangles to further limit the extent
of the text.
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drawsetdebug(on)
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Turns on or off debugging output (usually to a serial line) according
to whether on is non-zero.
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SOURCE
SEE ALSO
DIAGNOSTICS
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These routines call the graphics error function on fatal errors.
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BUGS
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Anti-aliased characters can be drawn by defining a font with multiple
bits per pixel, but there are no anti-aliasing geometric primitives.
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