Arc and Circle making are currently overly complicated. The operation of making both does not reflect the most practical and intuitive use. Several serious usability issues are combined in this report, because they are closely correlated and should best be handled together.


Arcs can currently only be drawn counter-clockwise, which most likely is the opposite of what is expected by most. Arcs and circles make funny movements along the vertical and horizontal lines through the first point set, so they usually do not reach their intended destination at all. The center can be set with the Alt-key however, but if the Alt-key is disengaged too early, they jump back again to an uncomprehensible location, if the first point set is not memorized; which is also never reached because the functions are looking for the horizontal and vertical intersection of that point. Even the most experienced users will most likely not be able to cope with this efficiently.

The most essential function of the Alt-key (draw around center), which tames the operation, is also not shown in the popup help menu, so most users will be totally left in the dark before studying the manual. At least the Arc function is close to unusable without a lot of dragging and shifting for a casual user as is.

LibO is not alone with this ergonomic catastrophe, other programs I have checked do not fare much better. So obviously a more sensible way of making Arcs and Circles has to be found, to turn these most basic operations into something usable.


The underlying cause of all of this is the inappropriate use of invisible virtual auxiliary lines, which should be avoided at all cost.
 

The most simple and straightforward solution is the markup and clear visualization of the center of these, then the rest can be drawn with ease and without surprise. This could be called a 'compass mode', which almost everybody should be able to use intuitively right away. The 'trick' is to always clearly mark the center (this is the most important common property of everything round) and do everything required afterwards in relation to the center.


Suggested solution, unified 'Compass Mode':

  - First click:  Clearly mark the center with a small cross, may even be red
                   for better visibility. Show a dimmed full circle afterwards
                   for visual guidance, as is, which is good.
                  (the center may then be erased later, but it is often
                   required in many types of formal drawings and may therefore
                   be left as is.
                   Automatic erasure should only be an option,
                   needs a tick box for that.)
                   
  - Second click:  Mark the radius, which also should be the starting point
                    of the Arc.
  
  - Third click:  This is the endpoint of the Arc. Allow *both* right and left
                   turns, to avoid complications and surprise.
                   
                   Delete the centerpoint, if automatic deletion of the
                   centerpoint is set in the Draw-Options, otherwise
                   it may be left as is. 
                   
                   A circle can be most easily drawn with the same function, 
                   if the endpoints meet. Otherwise an additional Circle
                   function is needed, that finishes after the second click.
                  
   - Elliptic Transformations:

                Could be just done by dragging the arc or circle at the sides.
                This eliminates another additional function.

                
With the above all Arcs, Circles and Ellipses could be drawn intuitively and easily with only one single function, with high precision, without surprise and without having to consult the manual first for such a basic operation.

Implementation should be possible with very little efford, since the basic functions are already all there. It should get a new icon with a pair of compasses shown, to clearly visualize the operation.


In addition the radius and the angle (vectorial coordinates) relative to the horizontal or vertical line could be shown next to the cursor (most simply just as a positive number of 0-45deg. to the closest main axis) to ease precise drawings (to be set as an Option).