An issue with a custom WindowKeyPressFcn (Interrupted)?

Hello. I am writing a simple game similar to the snake. To code the direction in which the snake will move next I am using a custom WindowKeyPressFcn. Since just like in the original game I want the snake to constantly move I am using a while loop with a pause(0.2) inside. However, once i start smashing buttons code freezes (no error, just freezes). I am assuming that I am interrupting the current function run and start another one and something goes wrong. Without the while loop everything works great. I tried to look into dbstack() and suck, but was unable to find multiple calls to WindowKeyPressFcn function. Setting Interruptible property of the figure "off" and "on" at the beginning/end of the loop did not help.

here is a full code:

if true 

function test

 step = 1;

 F=figure;
 A=axes;
 P=patch([2 2 3 3],[2 3 3 2],'r');
 set(A,'XLim',[-25 25],'YLim',[-25 25],'DataAspectRatio',[1 1 1]);
 seed_x = round(rand*49-25);
 seed_y = round(rand*49-25);
 food = patch([seed_x seed_x seed_x+1 seed_x+1],[seed_y seed_y+1 seed_y+1 seed_y],'g');

 set(F,'WindowKeyPressFcn',{@move,P,food,step}, ...
    'NumberTitle','off', ...
    'Name','Snake. Score: 0');
 end

 function move(~,event,L,f,s)
while 1
    if strcmpi(event.Key,'leftarrow')
        set(L,'XData',get(L,'Xdata') - s);
        eat(L,f);
        if any(get(L,'XData')<-25)
            set(L,'XData',[24 24 25 25]);
        end
    elseif strcmpi(event.Key,'rightarrow')
        set(L,'XData',get(L,'Xdata') + s);
        eat(L,f);
        if any(get(L,'XData')>25)
            set(L,'XData',[-25 -25 -24 -24]);
        end
    elseif strcmpi(event.Key,'uparrow')
        set(L,'YData',get(L,'Ydata') + s);
        eat(L,f);
        if any(get(L,'YData')>25)
            set(L,'YData',[-25 -24 -24 -25]);
        end
    elseif strcmpi(event.Key,'downarrow')
        set(L,'YData',get(L,'Ydata') - s);
        eat(L,f);
        if any(get(L,'YData')<-25)
            set(L,'YData',[24 25 25 24]);
        end
    end
    pause(0.2)
end
end

 function eat(I,fd)
 persistent score;
 if isempty(score)
    score=0;
 end

 a=get(I,'Xdata');
 b=get(I,'Ydata');
 c=get(fd,'Xdata');
 d=get(fd,'Ydata');
 if all(a == c) && all(b == d)
    score=score+1;
    set(gcf,'Name',['Snake. Score: ' num2str(score)]);
    sx = round(rand*49-25);
    sy = round(rand*49-25);
    set(fd,'Xdata',[sx sx sx+1 sx+1]);
    set(fd,'Ydata',[sy sy+1 sy+1 sy]);
 end
 end

end

Can I do anything to rectify the issue? Thanks in advance!

Answer 1

[Walter Roberson]

Instead of using a while loop with a pause(), use a timer() instead. Have your WindowKeyPressFcn only handle a single press. Set WindowKeyPressFcn interruptible off and BusyAction to the (default) 'queue'

[Aleksey]

Hello, thank you for a reply. I have never used timers before but it seems like exactly what I need. How do I set "interruptible" property for a function though or do I do it for the entire figure?

[Walter Roberson]

You do it for the entire figure.

http://www.mathworks.com/help/matlab/creating_guis/callback-sequencing-and-interruption.html