Thanks Dave! That all quite does the trick. Except one detail, I
found that the last step needed to be add to 90, not subtract from
90, in order to get the same results as PtToAngle().
thanks again,
Sophia
On Oct 25, 2007, at 3:29 AM, David A. Lyons wrote:
On Oct 24, 2007, at 8:02 PM, Sophia Poirier wrote:
PtToAngle() is deprecated in Mac OS X 10.4. What should we use as
a replacement? None of the documentations or headers I've found
have pointed towards a replacement.
What an odd function...I had never had occasion to use PtToAngle.
At its core, the equivalent is an "inverse tangent of (y / x)"
computation, but there are a few interesting details to consider.
PtToAngle adjusts for the aspect ratio of the rectangle you pass.
If you were using an empty rectangle (or any rectangle that is
square and is centered at (0,0)) then you can skip this part.
Otherwise, compute dy = point.y - rectCenterY and dx = point.x -
rectCenterX. Compute dy / dx and then multiply by rectWidth /
rectHeight to normalize the slope.
The arc-tangent (atan) of that value is your answer...but in
radians (counter-clockwise from right-equals-zero), and in the
range -pi/2 to pi/2. If dx was negative, add or subtract pi to
point the angle in the opposite direction.
If you need a result compatible with PtToAngle, convert to degrees,
and subtract from 90, and round off to an integer. At some point,
normalize the value into your preferred range by adding or
subtracting 360 degrees or 2pi radians.
I've glossed over some details, such as being careful about the dx
= 0 case. You may wish to check for that, or it may be sufficient
to let the floating-point result be Inf or -Inf, which atan can
handle properly.
Note that I haven't tested the above, only composed it here in
email (but with reference to the PtToAngle implementation in the
QuickDraw source).
Cheers,
--Dave (a.k.a. email@hidden)
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