Cairo.Arc (gb.cairo)
Static Sub Arc ( XC As Float, YC As Float, Radius As Float [ , Angle1 As Float, Angle2 As Float ] )
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XC : X position of the center of the arc.
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YC : Y position of the center of the arc.
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Radius : the radius of the arc.
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Angle1 : the start angle, in radians.
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Angle2 : the end angle, in radians.
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 * π until it is greater than
Angle1.
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. If this initial line is undesired, it can be avoided by calling
NewSubPath before calling
Arc.
Angles are measured in radians. An angle of
0.0 is in the direction of the positive X axis (in user space). An angle of
π/2.0 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 the
Rad() function.
This function gives the arc in the direction of increasing angles; see
ArcNegative 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:
Cairo.Save()
Cairo.Translate(X + Width / 2, Y + Height / 2)
Cairo.Scale(Width / 2, Height / 2)
Cairo.Arc(0, 0, 1, 0, Pi(2))
Cairo.Restore()