On Mar 18, 2007, at 9:57 PM, Maximilian Matthé wrote: > So how should one do a simple animation in fltk?
All GUI libraries are event based, which basically means that anything (or rather "any event") can happen at any time. You can't really think in a serial order. The user clicking on the start button is just one of many events, which changes the /state/ of your program. Before the click, the program was idling around. After the click, you are in "solving" state. In solving state, the program is supposed to show an animation step by step until some other event happens (the puzzle is solved, for example). But the human eye can only grasp 25 frames (or steps) per second, so there is no need to run the poor CPU at full speed. Just solve one step every 1/25th of a second. So what I would do is - write a callback function for the start button - in the callback function, call Fl::add_timeout(1/25.0, timerCB, 0) - now write another function, called timerCB - in timerCB, solve one step of the problem, don't draw anything - at the end of timerCB, if the puzzle is not solved yet, call Fl::repeat_timer(1.25.0, timerCB, 0) - as a last step, call MyWidget->redraw(); The button callback will start your timer. The timerCB will solve your puzzle (or animation) one step at a time and make sure that it will be called again in another 25th of a second. It will also tell your rendering widget to redisplay the changes you just calculated. Now implement MyWidget by deriving it from soem other widget and overriding the draw() function to erase the background and then draw your whole puzzle again using the dataset that was calculated in timerCB. Even though this may seem kind of backwards, this is by far the best way for a "simple" animation in an event-based system. It doesn't matter if your rendering is in OpenGL of FLTK code (or WIN32 GDI, if really needed, but you lose cross platform compatibility). Your other applications will thank you for not using more CPU time than needed, plus your program will always run at the same speed on all platforms. Matthias PS: exceptions: if you want to o as much calculation as possible during the display phases, or if you have overlapping calculations that are much longer than 1/25th of a second, you will be entering the wonderful field of multithreading... . ---- http://robowerk.com/ _______________________________________________ fltk mailing list [email protected] http://lists.easysw.com/mailman/listinfo/fltk
