From f16fed3d50fd3d56deb46a3d4641a81460e389de Mon Sep 17 00:00:00 2001 From: David Thompson Date: Wed, 12 Dec 2018 09:20:10 -0500 Subject: Update Chickadee manual and home page for 0.3.0. Better late than never! --- manuals/chickadee/Agendas.html | 221 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 221 insertions(+) create mode 100644 manuals/chickadee/Agendas.html (limited to 'manuals/chickadee/Agendas.html') diff --git a/manuals/chickadee/Agendas.html b/manuals/chickadee/Agendas.html new file mode 100644 index 0000000..eced92c --- /dev/null +++ b/manuals/chickadee/Agendas.html @@ -0,0 +1,221 @@ + + + + + + +Agendas (The Chickadee Game Toolkit) + + + + + + + + + + + + + + + + + + + + +
+

+Next: , Up: Scripting   [Contents][Index]

+
+
+ +

2.4.1 Agendas

+ +

To schedule a task to be performed later, an “agenda” is used. +There is a default, global agenda that is ready to be used, or +additional agendas may be created for different purposes. The +following example prints the text “hello” when the agenda has +advanced to time unit 10. +

+
+
(at 10 (display "hello\n"))
+
+ +

Most of the time it is more convenient to schedule tasks relative to +the current time. This is where after comes in handy: +

+
+
(after 10 (display "hello\n"))
+
+ +

Time units in the agenda are in no way connected to real time. It’s +up to the programmer to decide what agenda time means. A simple and +effective approach is to map each call of the update hook +(see Kernel) to 1 unit of agenda time, like so: +

+
+
(add-hook! update-hook (lambda (dt) (update-agenda 1)))
+
+ +

It is important to call update-agenda periodically, otherwise +no tasks will ever be run! +

+

In addition to using the global agenda, it is useful to have multiple +agendas for different purposes. For example, the game world can use a +different agenda than the user interface, so that pausing the game is +a simple matter of not updating the world’s agenda while continuing to +update the user interface’s agenda. The current agenda is dynamically +scoped and can be changed using the with-agenda special form: +

+
+
(define game-world-agenda (make-agenda))
+
+(with-agenda game-world-agenda
+  (at 60 (spawn-goblin))
+  (at 120 (spawn-goblin))
+  (at 240 (spawn-goblin-king)))
+
+ +
+
Procedure: make-agenda
+

Return a new task scheduler. +

+ +
+
Procedure: agenda? obj
+

Return #t if obj is an agenda. +

+ +
+
Procedure: current-agenda
+
Procedure: current-agenda agenda
+

When called with no arguments, return the current agenda. When called +with one argument, set the current agenda to agenda. +

+ +
+
Syntax: with-agenda agenda body …
+

Evaluate body with the current agenda set to agenda. +

+ +
+
Procedure: agenda-time
+

Return the current agenda time. +

+ +
+
Procedure: update-agenda dt
+

Advance the current agenda by dt. +

+ +
+
Procedure: schedule-at time thunk
+

Schedule thunk, a procedure of zero arguments, to be run at +time. +

+ +
+
Procedure: schedule-after delay thunk
+

Schedule thunk, a procedure of zero arguments, to be run after +delay. +

+ +
+
Procedure: schedule-every interval thunk [n]
+

Schedule thunk, a procedure of zero arguments, to be run every +interval amount of time. Repeat this n times, or +indefinitely if not specified. +

+ +
+
Syntax: at time body …
+

Schedule body to be evaluated at time. +

+ +
+
Syntax: after delay body …
+

Schedule body to be evaluated after delay. +

+ +
+
Syntax: every interval body …
+
Syntax: every (interval n) body …
+

Schedule body to be evaluated every interval amount of +time. Repeat this n times, or indefinitely if not specified. +

+ +
+
+

+Next: , Up: Scripting   [Contents][Index]

+
+ + + + + -- cgit v1.2.3