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;;; Sly
;;; Copyright (C) 2014 David Thompson <dthompson2@worcester.edu>
;;;
;;; This program is free software: you can redistribute it and/or
;;; modify it under the terms of the GNU General Public License as
;;; published by the Free Software Foundation, either version 3 of the
;;; License, or (at your option) any later version.
;;;
;;; This program is distributed in the hope that it will be useful,
;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
;;; General Public License for more details.
;;;
;;; You should have received a copy of the GNU General Public License
;;; along with this program. If not, see
;;; <http://www.gnu.org/licenses/>.
;;; Commentary:
;;
;; Live asset reloading.
;;
;;; Code:
(define-module (sly live-reload)
#:use-module (srfi srfi-1)
#:use-module (sly agenda)
#:use-module (sly coroutine)
#:use-module (sly game)
#:use-module (sly signal)
#:export (watch-files
with-live-reload))
(define* (watch-files files thunk #:optional (polling-interval 120))
"Watch FILES, a list of file names, and apply THUNK each time one of
them changes. A signal is returned that contains the current result
of THUNK. The POLLING-INTERVAL flag determines how often FILES are
polled for changes, defaulting to two seconds."
(define (current-mtime file-name)
(let ((info (stat file-name)))
(max (stat:mtime info) (stat:ctime info))))
(define (max-current-mtime)
(and (every file-exists? files)
(reduce max 0 (map current-mtime files))))
(let ((asset (make-signal (thunk))))
(coroutine
(let loop ((last-mtime (max-current-mtime)))
(wait polling-interval)
(let ((mtime (max-current-mtime)))
(when (cond
;; Game hasn't started yet.
((not (signal-ref game-started?)) #f)
;; Some files do not exist anymore, can't reload.
((not mtime) #f)
;; Some files were missing, but are back now.
((and mtime (not last-mtime)) #t)
;; All the files exist and existed last time, too, so
;; check if they have been modified since last time.
(else (> mtime last-mtime)))
(signal-set! asset (thunk)))
(loop mtime))))
asset))
(define* (with-live-reload proc #:optional (polling-interval 120))
"Return a new procedure that re-applies PROC whenever the associated
file is modified. The new procedure returns a signal that contains
the return value of PROC. The first argument to PROC must be a
file name string.
A simple polling method is used to test for updates. Files are polled
every POLLING-INTERVAL ticks (120 by default)."
(lambda (file-name . args)
(watch-files (list file-name)
(lambda () (apply proc file-name args)))))
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