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 2e3cbd32c1815358bef76f51890d122b96ab6d5f..3d05c9c4ce67037c6014a27b532f2b05802494a9 100644 (file)
--- 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 (file)
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)