lib/mnit/mnit_fps.nit

   1 # This file is part of NIT ( http://www.nitlanguage.org ).
   2 #
   3 # Licensed under the Apache License, Version 2.0 (the "License");
   4 # you may not use this file except in compliance with the License.
   5 # You may obtain a copy of the License at
   6 #
   7 #     http://www.apache.org/licenses/LICENSE-2.0
   8 #
   9 # Unless required by applicable law or agreed to in writing, software
  10 # distributed under the License is distributed on an "AS IS" BASIS,
  11 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  12 # See the License for the specific language governing permissions and
  13 # limitations under the License.
  14
  15 # Frame-rate control for applications
  16 module mnit_fps
  17
  18 import mnit_app
  19 private import realtime
  20
  21 redef class App
  22         # Limit the frame-rate to a given frequency
  23         # This basically limits how much `frame_core` is called per second.
  24         # Zero (or a negative value) means no limit.
  25         #
  26         # Applications can modify this value even during the main-loop.
  27         var maximum_fps writable = 60
  28
  29         redef fun full_frame
  30         do
  31                 super
  32                 limit_fps
  33         end
  34
  35         # The clock for limit_fps
  36         private var clock = new Clock
  37
  38         # Check and sleep to maitain a frame-rate bellow `maximum_fps`
  39         # Is automatically called at the end of `full_frame`.
  40         fun limit_fps
  41         do
  42                 var mfps = maximum_fps
  43                 if mfps <= 0 then return
  44                 var dt = clock.lapse
  45                 var target_dt = 1000000000 / mfps
  46                 var sec = dt.sec
  47                 var nanosec = dt.nanosec
  48                 if sec == 0 and nanosec < target_dt then
  49                         var sleep_t = target_dt - nanosec
  50                         sys.nanosleep(0, sleep_t)
  51                         dt = clock.lapse
  52                 end
  53         end
  54 end