lib/mnit: introduce mnit_fps so each app does not need to play with clocks

Signed-off-by: Jean Privat <jean@pryen.org>

diff --git a/lib/mnit/mnit.nit b/lib/mnit/mnit.nit
index 3e313d4..53c4681 100644 (file)
--- a/lib/mnit/mnit.nit
+++ b/lib/mnit/mnit.nit
@@ -21,3 +21,4 @@ import mnit_app
 import opengles1
 import assets
 import numbers
+import mnit_fps

diff --git a/lib/mnit/mnit_fps.nit b/lib/mnit/mnit_fps.nit
new file mode 100644 (file)
index 0000000..38f0d48
--- /dev/null
+++ b/lib/mnit/mnit_fps.nit
@@ -0,0 +1,54 @@
+# This file is part of NIT ( http://www.nitlanguage.org ).
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+# Frame-rate control for applications
+module mnit_fps
+
+import mnit_app
+private import realtime
+
+redef class App
+       # Limit the frame-rate to a given frequency
+       # This basically limits how much `frame_core` is called per second.
+       # Zero (or a negative value) means no limit.
+       #
+       # Applications can modify this value even during the main-loop.
+       var maximum_fps writable = 60
+
+       redef fun full_frame
+       do
+               super
+               limit_fps
+       end
+
+       # The clock for limit_fps
+       private var clock = new Clock
+
+       # Check and sleep to maitain a frame-rate bellow `maximum_fps`
+       # Is automatically called at the end of `full_frame`.
+       fun limit_fps
+       do
+               var mfps = maximum_fps
+               if mfps <= 0 then return
+               var dt = clock.lapse
+               var target_dt = 1000000000 / mfps
+               var sec = dt.sec
+               var nanosec = dt.nanosec
+               if sec == 0 and nanosec < target_dt then
+                       var sleep_t = target_dt - nanosec
+                       sys.nanosleep(0, sleep_t)
+                       dt = clock.lapse
+               end
+       end
+end