On 9/2/21 10:03 PM, Greg Ercolano wrote:

On 9/2/21 6:38 PM, Bill Spitzak wrote:

It does seem like a bug, calling value() should not have any side-effects. Especially because the tabs widget works even if nobody calls value().

    Ah, it is weird that just testing with Fl_Tabs::value(void) can apparently
    end up calling hide() and show().. yikes.

    That code goes back to 1999 though, so looks like you'd know for sure:

49a0693962 (Matthias Melcher   2006-08-17 13:43:07 +0000 308) Fl_Widget* Fl_Tabs::value() {
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 309)   Fl_Widget* v = 0;
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 310)   Fl_Widget*const* a = array();
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 311)   for (int i=children(); i--;) {
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 312)     Fl_Widget* o = *a++;
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 313)     if (v) o->hide();
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 314)     else if (o->visible()) v = o;
a7904da09a (Bill Spitzak       1999-10-15 09:01:48 +0000 315)     else if (!i) {o->show(); v = o;}
f9039b2ae2 (Michael R Sweet    1998-10-06 18:21:25 +0000 316)   }
f9039b2ae2 (Michael R Sweet    1998-10-06 18:21:25 +0000 317)   return v;
f9039b2ae2 (Michael R Sweet    1998-10-06 18:21:25 +0000 318) }

   Perhaps that's the cause, because that last line in the loop that
   calls o->show() on the last item seems to be maybe what's forcing
   the last child to be visible if no other one is..

    ..and by that I mean the loop code in Fl_Tabs::value(Fl_Widget*) that changes
    the selected tab by hide()ing all but the one to be show()n
    gets confused when it reaches the last tab and finds it visible() before it show()s it,
    causing the loop to think there was no change when there in fact was.

    It would appear Fl_Widget* value(void) seems to enforce that:

        > Not more than one group is visible
        > That at least one group is visible (the last, if no others are)

    And that sounds like a good thing to enforce at least /somewhere/,
    as it's hard to imagine the Tabs widget with no group visible, and/or
    more than one group visible at a time.

    So perhaps the fix I suggested is the right one, assuming we want to
    leave the value(void) code alone, and the show() FL_HIDE/FL_SHOW event behavior
    is correct.

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