cairo:matrix-rotate (matrix angle)

matrix -- a cairo:matrix-t instance
angle -- a number coerced to a double float for the angle of rotation, in radians

The cairo:matrix-t instance with the applied rotation.

Applies rotation by angle to the transformation in the matrix. The effect of the new transformation is to first rotate the coordinates by angle, then apply the original transformation to the coordinates.

The direction of rotation is defined such that positive angles rotate in the direction from the positive X axis toward the positive Y axis. With the default axis orientation of Cairo, positive angles rotate in a clockwise direction.