Data commit

Task/Animation/Prolog/animation.pro

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+:- use_module(library(pce)).
+
+animation :-
+    new(D, window('Animation')),
+    new(Label, label(hello, 'Hello world ! ')),
+    send(D, display, Label, point(1,10)),
+    new(@animation, animation(Label)),
+    send(D, recogniser,
+         new(_G, my_click_gesture(left, ''))),
+
+    send(D, done_message, and(message(@animation, free),
+                  message(@receiver, destroy))),
+    send(D, open),
+    send(@animation?mytimer, start).
+
+
+:- pce_begin_class(animation(label), object).
+variable(label, object,  both, "Display window").
+variable(delta,    object, both,  "increment of the angle").
+variable(mytimer, timer, both, "timer of the animation").
+
+initialise(P, W:object) :->
+        "Creation of the object"::
+        send(P, label, W),
+        send(P, delta, to_left),
+    send(P, mytimer, new(_, timer(0.5,message(P, anim_message)))).
+
+% method called when the object is destroyed
+% first the timer is stopped
+% then all the resources are freed
+unlink(P) :->
+    send(P?mytimer, stop),
+    send(P, send_super, unlink).
+
+
+% message processed by the timer
+anim_message(P) :->
+    get(P, label, L),
+    get(L, selection, S),
+    get(P, delta, Delta),
+    compute(Delta, S, S1),
+    new(A, name(S1)),
+    send(L, selection, A).
+
+
+:- pce_end_class.
+
+:- pce_begin_class(my_click_gesture, click_gesture,
+           "Click in a window").
+
+class_variable(button, button_name, left,
+           "By default click with left button").
+
+terminate(G, Ev:event) :->
+    send(G, send_super, terminate, Ev),
+    get(@animation, delta, D),
+    (   D = to_left -> D1 = to_right; D1 = to_left),
+    send(@animation, delta, D1).
+
+:- pce_end_class.
+
+
+% compute next text to be dispalyed
+compute(to_right, S, S1) :-
+    get(S, size, Len),
+    Len1 is Len - 1,
+    get(S, sub, Len1, Str),
+    get(S, delete_suffix, Str, V),
+    get(Str, append, V, S1).
+
+compute(to_left, S, S1) :-
+    get(S, sub, 0, 1, Str),
+    get(S, delete_prefix, Str, V),
+    get(V, append, Str, S1).