scripting: Add custom polling support.

1 files changed, 20 insertions, 0 deletions

diff --git a/doc/api.texi b/doc/api.texi
index 9cfa26a..446460e 100644
--- a/doc/api.texi
+++ b/doc/api.texi
@@ -3985,6 +3985,15 @@ Schedule @var{body} to be evaluated every @var{interval} amount of
 time.  Repeat this @var{n} times, or indefinitely if not specified.
 @end deffn
 
+It is also possible to schedule things that are not dependent on how
+much time passes.  The agenda will periodically poll to see if any
+registered conditions are met.
+
+@deffn {Procedure} call-when pred thunk
+Call @var{thunk} sometime in the future when @var{pred} is satisfied
+(returns a value other than @code{#f}.)
+@end deffn
+
 @node Scripts
 @subsection Scripts
 
@@ -4070,6 +4079,17 @@ procedure @var{handler}.
 Wait @var{duration} before resuming the current script.
 @end deffn
 
+@deffn {Syntax} wait-until condition
+Wait until @var{condition} is met before resuming the current script.
+
+@example
+(script
+  (wait-until (key-pressed? 'z))
+  (display "you pressed the Z key!\n"))
+@end example
+
+@end deffn
+
 @deffn {Syntax} forever body @dots{}
 Evaluate @var{body} in an endless loop.
 @end deffn