From: Javier Sancho <jsf@jsancho.org>
Date: Mon, 13 Jan 2014 05:51:52 +0000 (+0100)
Subject: Do step duration properly
X-Git-Url: https://git.jsancho.org/?p=gacela.git;a=commitdiff_plain;h=8864bc71fcf9fd551bdb417a1b22655a9097dd30

Do step duration properly

* src/engine.scm: use step start time and end time for calculating
                  delay and step duration

* src/misc.scm: new function 'current-utime' that gets current time
                in microseconds
---

diff --git a/src/engine.scm b/src/engine.scm
index 2e3cbd3..3d05c9c 100644
--- a/src/engine.scm
+++ b/src/engine.scm
@@ -16,6 +16,7 @@
 
 
 (define-module (gacela engine)
+  #:use-module (gacela misc)
   #:use-module (gacela system)
   #:use-module (ice-9 receive)
   #:use-module (ice-9 threads)
@@ -56,10 +57,10 @@
 
 ;;; Engine Inner Properties
 
-(define (default-delay) 0.1)
+(define (default-step) 0.1)
 
 (define (default-engine-inner-properties)
-  `(engine-inner-properties (delay . ,(default-delay))))
+  `(engine-inner-properties (step . ,(default-step))))
 
 
 ;;; Engine definitions
@@ -175,12 +176,15 @@
   (cond ((not (engine-running? engine))
 	 (with-mutex (engine-running-mutex engine)
 	   (let loop ()
-	     (let ((delay 0))
+	     (let ((t (current-utime))
+		   (delay 0))
 	       (with-engine engine
 	         (receive (e c) ((apply (engine-system engine) (engine-entities engine)))
 		   (set-engine-entities! engine (list e c)))
-		 (set! delay (get-property '(engine-inner-properties delay))))
-	       (usleep (inexact->exact (* delay 1000000))))
+		 (set! delay (- (inexact->exact (* (get-property '(engine-inner-properties step)) 1000000))
+				(- (current-utime) t))))
+	       (cond ((> delay 0)
+		      (usleep delay))))
 	     (if (not (engine-stopping? engine #:clean #t))
 		 (loop)))))))
 
diff --git a/src/misc.scm b/src/misc.scm
new file mode 100644
index 0000000..66bcf6f
--- /dev/null
+++ b/src/misc.scm
@@ -0,0 +1,25 @@
+;;; Gacela, a GNU Guile extension for fast games development
+;;; Copyright (C) 2014 by Javier Sancho Fernandez <jsf at jsancho dot org>
+;;;
+;;; 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/>.
+
+
+(define-module (gacela misc))
+
+
+(define (current-utime)
+  (let ((t (gettimeofday)))
+    (+ (* (car t) 1000000) (cdr t))))
+
+(export current-utime)