Creating user friendly programs (6)
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by Steven Flintham (15A)
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Interacting with the user (3)
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The last two articles in this series  have covered direct and step selection
menus. This time  I want to introduce the combined  step-and-direct menu, an
example of which is provided by the example BASIC program SD1. This is based
on the Step2 program from the last article.

Step-and-direct menus  have the  the advantages of  both step  selection and
direct choice menus,  the only disadvantage being the small  amount of extra
code necessary to implement them.

The first change  is in lines 340-380, where alternative  direct choices are
printed over  at the  right hand side  of the  screen. Their  positioning is
arbitrary, although I  think that this arrangement is  probably the neatest.
Key shortcuts, as  these keys are known,  are not provided for  all the menu
options - this is just done to make the point that it is possible.

In a real program, you could provide  shortcuts for all of the menu options,
or just for  the most frequently used  ones depending on the  situation. For
instance, you could  miss shortcuts from the "dangerous"  menu options (e.g.
format  disc, delete  file)  to  help to  reduce  the  risk of  accidentally
selecting them.

The "input" loop in lines 440-470 has  been extended so that only keys which
serve  a useful  function  are accepted.  This  was not  done  in the  other
programs in this series - it is not  essential, but it does prevent the menu
bar flickering when a non-menu key is pressed.

Finally, lines  510-550 simply set  choice% to  the appropriate line  of the
menu if a shortcut has been selected.  Line 510 converts lower case to upper
case  if CAPS  LOCK is  off, which  is  quite important  in a  user-friendly
program. One  possible enhancement would  be to convert  "!" to "1",  "#" to
3,... in  case SHIFT LOCK  is engaged, but  this has  not been done  in this
example since it is not possible to do it in a small amount of code as there
is no convienient  ASCII relationship between the numbers  and their shifted
equivalents (or will someone prove me wrong?)

This particular version still requires the  user to press RETURN after using
a shortcut. If you don't want this facility,  the code can be modified as in
SD2. This simply  sets key% to 13  after resetting choice% so  that the menu
loop terminates immediately.

SD3 is a step-and-direct version of the rolling bar menu from last issue. It
works in  the same way as  SD1, and so it  should be fairly easy  to follow.
Note, however, that the bar is  redrawn immediately after setting choice% to
its new value, rather than after all the key shortcuts have been considered.
This is  due to the  way in which this  menu works -  it is not  possible to
remove the  bar, set  choice% in  a series  of IF-THEN  statements and  then
restore it because the animation of the bar depends on the key pressed.

Secondly, note  that PROCdelay(2)  has been  appended to  the IF  offset%<>0


THEN... line in order to avoid the scrolling effect when moving the menu bar
directly to an option.

That's about it as  far as menus are concerned. In the  next article, I will
cover some of the other forms of user input.