assigned to current CVS since it is a wishlist item

I am not sure about this...  Using a minus sign would be closer to
the mathematical usage, and therefore some users could expect that
it would use the trigonometric conventions (the positive rotations
are anti-clockwise).  Maybe it is just me, but when I see some angles
given without +/- signs I expect the clockwise order, and when I see
angles given as +90 or -90 I expect the trigonometric order.

No, it's just you ;) Ask some people about how they would interpret
such items in the context of rotation and you will see ;)

alternatively, "270 degs" could be renamed to "90 degs anticlockwise"
or so.

Hmmm...  To avoid any confusion, it would probably be better to
rename the thee rotation options as follows:
  ...->Layers->Rotate->90 degrees clockwise
  ...->Layers->Rotate->180 degrees
  ...->Layers->Rotate->90 degrees anticlockwise
This is a bit long, but this is the best compromise IMHO.

I dont think using -90 would be clear enough for people with bad
vision, and if you are in hurry it is a very small and subtle
difference.  

Specifying clockwise and anticlockwise seems overly verbose and is
just making work for the translators.  Compromise usually means no one
gets what they actually want.  

Some programs such as Visio use 
Rotate Right   Ctrl+R   which is 90 degrees clockwise
Rotate Left    Ctrl+L   which is 270 degrees clockwise, 90 degrees
anticlockwise.  

It is not unreasonable to leave out Rotate 180 because it is exactly
the same as Flip Horizontal and can also be acheived by simply
rotating 90 degrees twice.  

Most people use other programs besides the gimp, consistancey is
important, it makes it easier to learn and remember.  

Anyone know what Photoshop does?

IMO we should simply add some icons here.

Menu icons would be great as well, but that should nearly be a
seperate enhancement.  

You might be able to borrow icons from Sodipodi or Sketch (i know Dia
does not have icons for rotate).  

If someone could verify that appropriate icons dont already exist then
i will try and draw some, which will for consistancey and learnability
strongly resemeble the Rotate Icons that appear in various Microsoft
programs such as Visio for example.  
(16x16 pixels? any particular colour palette? ximian?)

There already are icons for this purpose:

http://developer.gimp.org/api/1.3/libgimpwidgets/libgimpwidgets-GimpStock.html#GIMP-STOCK-ROTATE-180-CAPS

Similarity to icons in Microsoft software is definitely not an
argument for or against an icon. There are other guidelines that
define what makes up a good icon.

The reason why the icons are not already in use is simply that the
current implementation of the rotate feature is a plug-in and plug-ins
can not (yet) register icons. We'd have to special-case the rotate
plug-in or simply move the functionality to the core.

Already existing icons, cool.  (I'll see if Dia could use some of them).  

Copy is not a great arguement for or against anything but it has the
minor advantage of consistancey at the very least rather than making
whole new mistakes and confusing users in new and unusual ways.  
Ideally of course we would have time to think through the how and why,
study the usability issues and make better icons.  

I did not realise that Rotate was a plugin (guess i need to read more
code).  
Sorry to go a little off topic here but would it be possible to
reorganise it so that there is just one Rotate menu and that it Gimp
would rotate Layer/Selection/Image based on context?  
Duplicate menus are somewhat useful but i think this utility is
outweighed by usability issue of it just being confusing.  

I'd just like to point out the fact that rotating 180 degrees is not
the same as flipping horizontally.

oops, 
allow me to rephrase

It is not unreasonable to leave out Rotate 180 because it equivalent 
to Flip Horizontal then Flip Vertical, or Rotating 90 degrees twice.  

I may as well take this time to mention that it would be useful to 
have Flip Horizontal, Flip Vertical as it would allow me to add a 
keybinding and Flip more directly with a single key combination rather 
than having to change to the flip tool and use the mouse.  

Fixed in CVS. We have changed the menu entries to say "Rotate Left,
Rotate Right, Rotate 180 degrees" and added icons to illustrate their
meaning. We have also added menu entries for "Flip Horizontally" and
"Flip Vertically".

I disagree with the way this was fixed: "left" and "right" have no
meaning for a rotation because some people assume that the reference
point is at the top of the object, while others assume that it is at
the bottom.  I don't know if it is related to the education, culture,
shape of the object, or just the current mood of the person trying to
rotate something, but in any case I think that "left" and "right" do
not help and should be replaced by "clockwise" and "counter-clockwise"
(or "anti-clockwise"?).

I know that the icons can help, but the labels should be changed in
order to avoid any possible confusion.

Raphaël - are you sure that this is the case? Rotating to the left or
right is a well known term and to my knowledge always refers to the
topmost point or the point pointing away from someone.

There are famous clocks in germany - so called bavarian clocks - that
run backwards, so that "clockwise" and "anticlockwise" would lose
their meaning. This however does not justify the assumption that they
are useless for communicating the direction of a rotation.

Please back up your claim with facts (I.e. there *are* a significant
number of people who take the bottom as reference).

Currently, the only way for me to back up my claim would be to show
you the colleague of mine (as well as another friend of mine) who
almost consistently took the "wrong" reference point when we talked
about rotations (for the record, they aren't suffering from dyslexia). 
And you would of course say that I bribed him to do that, so basically
I have no proof.  :-)

But there was a previous comment from Alan asking "Anyone know what
Photoshop does?".  Well, I checked and the options for rotation are:
  180°
  90° CW  (clockwise)
  90° CCW (counter-clockwise)
  Arbitrary...
So even if we should not try to copy Photoshop for everything, I
assume that they had some reasons for not using "left" and "right".

Raphael, you don't really beleive that the metaphor of
turning something left or right is dependant on culture
and education?

It's IMHO absolulely clear what's meant by "turn left" or
"turn right", otherwise cars won't work the same all over
the place: turn the wheel left to drive to the left ;-)

(As a sidenote: earlier in this thread there was the
consensus that "-90" mathematically means "clockwise".
This is not true for the GIMP, since our coordinate
system is left-handed, so the positive rotate direction
is clockwise, not counter-clockwise. GIMP was using
the mathematically right numbers all the time).

Anyway, personally, I find "left" and "right" much more
intuitive then CW and CCW...

What about 

Rotate 90 deg. CCW (left)
Rotate 90 deg. CW (right)
Rotate 180 deg.

?

Regarding the education or culture thing, I said that I didn't know.
And there is probably no correlation anyway.  But one of the guys who
was frequently arguing with me about left and right rotations was
from New Zealand.  It would be hilarious if he was thinking "in the
opposite direction" because of his origins.  More seriously, this is
probably just a personal thing.  Or more likely related to the object
or image to be rotated.

By the way, the analogy with the cars is incorrect, because that
rotation is on the horizontal plane and always relative to the
direction that you are facing when driving.  The relation is not so
obvious when you are looking at a computer screen, except if you are
looking down at a TabletPC.

I have just found an image that could confuse some users because the
mental link "left/right" would go against what is shown (and written)
in the picture.  I will attach it below.  I have cropped it and
modified it a bit to show only the interesting parts.  If you look at
that image, you would probably be confused about what "rotate left"
would do.  There could be a similar confusion with other images
showing some objects from below or any image that has a natural
reference point near its bottom.  Of course, this is a silly example
that does not represent the majority of images that people could be
working on.  I expect that someone could take a snapshot of a bavarian
clock to confuse people about what "clockwise" means.

Anyway, this problem can be solved with Mitch's suggestion and I like
it:
  Rotate 180°
  Rotate 90° CW  (right)
  Rotate 90° CCW (left)

Created attachment 16699 [details]
Silly example of a confusing image (JPEG, 13 KB)

Abbreviations like CW and CCW are really not an option.

And we can not use '°' since we'd force people to use gettext >= 0.12
then (which supports UTF-8 msgids). What we can do is provide an en_US
translation that translates "degress" (or perhaps "deg.") into '°'.

IMO the icons illustrate it well enough, but that is just my personal
opinion ...

Photoshop uses CW and CCW.  It looks like the users are happy with that,
so I don't understand why this could not be an option for the GIMP.  I
do not have Photoshop myself, but a little Googling gave me a page with
a screenshot of the Image->Rotate menu in Photoshop:
http://www.pausd.palo-alto.ca.us/edtech/techtosa/online-handbook/publishing/photo-adjust.html
By the way, having "Arbitrary..." in that menu is not a bad idea.  That
explains why we get so many questions about how to perform arbitrary
rotations in the GIMP.

"Because Photoshop does it" is a rather bad argument. Did you ask any
Photoshop users if they are happy with it? CW and CCW are uncommon
abbreviations and I bet that they say less than "Left" or "Right" to
most people.

Adding arbitrary rotations would be a major undertaking and I'd rather
teach people to use the rotate tool for that.

Fixed in CVS:

2003-06-06  Michael Natterer  <mitch@gimp.org>

	* app/gui/image-menu.c: added CW/CCW to the "Rotate" menu entries
	as suggested in bug #57797. Cleaned up image_menu_update().

sven, 
for Abitrary rotation (which btw should probably be labelled
Rotate...) why not just popup the dialog "Rotation Information".  

This would be a lot more efficient, poweful and usable, than forcing
the user to:
1) choose the Tool for "Rotation scaling shearing perspective" 
2) making sure it was correctly set to the Rotation 
(which granted is the default) 
3) and then clicking on the image/current selection rather.  

should i file a seperate request?

Yes, perhaps it makes sense to add a menu entry that calls the Rotate
tool. Although it is a lot easier to find in 1.3 already. BTW, you
should really be using 1.3 if you want to suggest GUI enhancements.
Basing your suggestions on 1.2 doesn't help much.

Sorry, I will try harder to check before posting.  
I do have 1.3.11 on my home machine 
(need to try again to update to 1.3.14)

Thanks for listening.