diff options
| -rw-r--r-- | sly/signal.scm | 36 |
1 files changed, 30 insertions, 6 deletions
diff --git a/sly/signal.scm b/sly/signal.scm index e57e880..a35f042 100644 --- a/sly/signal.scm +++ b/sly/signal.scm @@ -33,6 +33,9 @@ define-signal signal-let signal-let* hook->signal + add-signal-hook! + remove-signal-hook! + clear-signal-hook! signal-ref signal-ref-maybe signal-set! @@ -66,12 +69,15 @@ ;; programming. State mutation is hidden away and a functional, ;; declarative interface is exposed. (define-record-type <signal> - (%%make-signal value proc inputs outputs) + (%%make-signal value proc inputs outputs hook) %signal? (value %signal-ref %%signal-set!) (proc signal-proc) (inputs signal-inputs) - (outputs signal-outputs)) + (outputs signal-outputs) + ;; Hook for escaping the signal graph to perform side-effects like + ;; file I/O, playing sounds, etc. + (hook signal-hook)) (define-record-type <signal-box> (make-signal-box signal) @@ -92,7 +98,9 @@ (define (%make-signal init proc inputs) "Create a new signal with initial value INIT." - (let ((signal (%%make-signal init proc inputs (make-weak-key-hash-table)))) + (let ((signal (%%make-signal init proc inputs + (make-weak-key-hash-table) + (make-hook 1)))) (for-each (cut signal-connect! signal <>) inputs) signal)) @@ -105,6 +113,20 @@ procedure PROC, and a list of INPUTS." (make-signal-box (%make-signal init proc inputs))) +(define (add-signal-hook! signal proc) + "Add PROC, a procedure that accepts a single argument, to the hook +associated with SIGNAL. When SIGNAL receives a new value, PROC will +be applied with that value." + (add-hook! (signal-hook (signal-unbox signal)) proc)) + +(define (remove-signal-hook! signal proc) + "Remove the procedure PROC from the hook associated with SIGNAL." + (remove-hook! (signal-hook (signal-unbox signal)) proc)) + +(define (clear-signal-hook! signal) + "Remove all hooks associated with SIGNAL." + (reset-hook! (signal-hook (signal-unbox signal)))) + (define (signal-connect! signal-out signal-box-in) "Attach SIGNAL-OUT to SIGNAL-BOX-IN. When the signal within SIGNAL-BOX-IN changes, the value will be propagated to SIGNAL-OUT." @@ -123,9 +145,11 @@ Otherwise, return OBJECT." (define (signal-propagate! signal) "Notify all output signals about the current value of SIGNAL." - (hash-for-each (lambda (output unused) - ((signal-proc output) output (%signal-ref signal))) - (signal-outputs signal))) + (let ((value (%signal-ref signal))) + (run-hook (signal-hook signal) value) + (hash-for-each (lambda (output unused) + ((signal-proc output) output value)) + (signal-outputs signal)))) (define (%signal-set! signal value) "Change the current value of SIGNAL to VALUE and propagate VALUE to |