Description
Adds a circular arc of the given radius to the current path. The
arc is centered at (xc, yc), begins at angle1 and proceeds in
the direction of increasing angles to end at angle2. If angle2 is
less than angle1 it will be progressively increased by 2*M_PI
until it is greater than angle1.Usage
cairoArc(cr, xc, yc, radius, angle1, angle2)
Arguments
xc
[numeric] X position of the center of the arc
yc
[numeric] Y position of the center of the arc
radius
[numeric] the radius of the arc
angle1
[numeric] the start angle, in radians
angle2
[numeric] the end angle, in radians
Details
If there is a current point, an initial line segment will be added
to the path to connect the current point to the beginning of the
arc.
Angles are measured in radians. An angle of 0 is in the direction
of the positive X axis (in user-space). An angle of M_PI radians
(90 degrees) is in the direction of the positive Y axis (in
user-space). Angles increase in the direction from the positive X
axis toward the positive Y axis. So with the default transformation
matrix, angles increase in a clockwise direction.
(To convert from degrees to radians, use degrees * (M_PI /
180.).)
This function gives the arc in the direction of increasing angles;
see cairoArcNegative to get the arc in the direction of
decreasing angles.
The arc is circular in user-space. To achieve an elliptical arc,
you can scale the current transformation matrix by different
amounts in the X and Y directions. For example, to draw an ellipse
in the box given by x, y, width, height:
cr$save()
cr$translate(x + width / 2, y + height / 2)
cr$scale(1 / (height / 2), 1 / (width / 2))
cr$arc(0, 0, 1, 0, 2 * pi)
cr$restore()