Fabio Bracci wrote:
> a) why is draw() a protected method?
Because normally the user should not call draw the widgets explicitly,
it is drawn when needed within Fl::flush() - ie within Fl::run() loop.
HOWEVER draw() of Fl_Widget is public!
So there is nothing to stop you to downcast and access it anyway - like
((Fl_Widget *)my_group)->draw();
> b) how to trigger draw()? I'm thinking of a group->hide(); group->show()
> sequence, but it seems clumsy to me ...
You can trigger it by
my_group->redraw();
but there is even better way as above call may make dirty also
particular screen window regions which would need to be redrawn with
next call to Fl::flush() within UI loop. To avoid that, it is better and
faster to only set damage flags using
Fl_Widget::clear_damage(FL_DAMAGE_ALL) call. But we need to assure that
at that moment the screen up-to-date and we do not interfere wit the UI
updating loop - so we will call Fl::flush() first. Aftrer drawing we can
safely clean the the damage flags back. So the code sequence would be:
Fl::flush(); // now everything should be clean
// and screen is up-to-date
my_group->clear_damage(FL_DAMAGE_ALL); // makes it dirty
// without destroying regions
((Fl_Widget *)my_group)->draw(); // now it should draw just fine
my_group->clear_damage(0); // makes it clean again
Roman
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