That makes sense. Thanks for the help.
> Kevin Cockrell wrote:
> > Hi,
> > I setup a very simple fltk GUI with Fl_Window that has a Fl_Menu_Bar and
> > an Fl_Gl_Window. I have the following items in my menu (which is called
> > mbar):
> >
> > mbar->add("ChangeSquareColors/Make Square Red", 'r',
> > (Fl_Callback*)TopSide_GUI::cb_MakeSquareRed, (void*)0, 0);
> > mbar->add("ChangeSquareColors/Make Square Blue", 'b',
> > (Fl_Callback*)TopSide_GUI::cb_MakeSquareBlue, (void*)0, 0);
> >
> > Inside of my Fl_Gl_Window draw() function, I just draw a square that is red
> > or blue according to a variable that is set with the callback functions
> > from the menu.
> >
> > But I am running into something that confuses me. If I use a mouse to click
> > on the menu and choose one of the items, then it automatically calls the
> > draw() function of my Fl_Gl_Window. But if I use the shortcuts 'r' or 'b',
> > it changes the local variable but does not call the draw() function. Why
> > is clicking on the menu different than using the kayboard shortcuts?
>
> When you click on the menu, the menu is probably posting over the
> opengl window, damaging it. When the menu clears, fltk tells the
> damaged widget (the opengl window) to redraw.
>
> Keyboard shortcuts don't post damaging graphics,
> so no redraw is needed.
>
> If your callback is changing things in the opengl window,
> then you'll need to force a redraw for the opengl widget
> to force it to redraw; to do that, use yourglwindow->redraw();
> in your callback after making the color change. This will schedule
> FLTK to redraw the widget, which it should do when you return
> from the callback.
>
> > And how does my Fl_Menu_Bar "know" that there is a Fl_Gl_Window
> > to draw? This seems very weird to me...
>
> The menubar doesn't; FLTK does.
>
> FLTK knows about all the widgets, and is responsible for managing
> redrawing them in the correct order.
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