I've just written a Clock View myself and came up against the same
problem. Theoretically since NSAffineTransform is just a mathematical
transformation matrix so it is possible - but I couldn't find a way
to do it. Not knowing the internals of the class it might involve
subclassing to use a 3x3 matrix.
I solved it instead by constructing the clock face and hands about
the origin using NSAffineTransform as usual to rotate the various
parts correctly. Then I used another affine transform to move the
bezier paths into the centre of the view.
There's an example project in your /Developer/Examples/AppKit/
ClockControl folder that you may find useful, I used the equations
that calculate how many degrees to rotate by from this project as the
basis for mine.
Also something to bear in mind is that the NSAffineTransform rotate
methods rotate anti-clockwise when passed a positive value (this is
due to the way that the transformation matrix is setup), pass them a
negative value to perform clockwise rotation.
- Keith
On 4 Mar 2007, at 10:07, Ken Tozier wrote:
Hi
I'm writing a clock class and am having some trouble getting the
hands to rotate around the center of the view using an
NSAffineTransform. As it stands now, it's rotating the hands around
the lower left corner of the view. Is there any way to set the draw
origin of the view to the center without moving the view itself?
Alternately, is there a way to define a transform so that it
rotates from a specified point rather than the lower left corner?
Thanks
Ken
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