Merge: gamnit: use the same code to limit fps than mnit and fix errors

Fixed a few bugs in `mnit::mnit_fps`, a typo invalidated the value of `current_fps` and the use of long Ints were broken probably since they are tagged. Using floats should fix this last issue.

Finally, the goal of this PR is to copy the module `mnit::mnit_fps` to `gamnit::limit_fps` and adapt it to the gamnit framework. There is some code duplication, but the mnit version should be deleted with the engine when gamnit is completed.

Pull-Request: #1879
Reviewed-by: Jean Privat <jean@pryen.org>

Author: privat

contrib/crazy_moles/src/moles.nit

@@ -318,7 +318,7 @@ redef class App
 	do
 		super
 
-		maximum_fps = 50
+		maximum_fps = 50.0
 	end
 
 	redef fun frame_core(display)

contrib/tinks/src/client/client.nit

@@ -80,7 +80,7 @@ redef class App
 	redef fun on_create
 	do
 		super
-		maximum_fps = 60
+		maximum_fps = 60.0
 		assets.assign_images_to_story context.game.story
 	end
 
@@ -127,7 +127,7 @@ redef class App
 			return new LocalServerContext
 		else
 			print "Connecting to:{address}:{port}"
-			maximum_fps = 0
+			maximum_fps = 0.0
 
 			# Args are: tinks server_address {port}
 			#var address = "riph" # args[0]

examples/mnit_ballz/src/ballz_android.nit

@@ -38,7 +38,7 @@ redef class App
 		gyroscope.enabled = true
 		light.enabled = true
 		proximity.enabled = true
-		maximum_fps = 50
+		maximum_fps = 50.0
 		sensors_support_enabled = true
 		super
 	end

examples/mnit_ballz/src/ballz_linux.nit

@@ -29,7 +29,7 @@ redef class App
 
 	redef fun run
 	do
-		maximum_fps = 50
+		maximum_fps = 50.0
 		super
 	end
 

examples/mnit_dino/src/dino.nit

@@ -39,7 +39,7 @@ redef class App
 	do
 		super
 
-		maximum_fps = 80
+		maximum_fps = 80.0
 
 		var display = display
 		assert display != null

lib/core/time.nit

@@ -32,6 +32,16 @@ redef class Sys
 	`}
 end
 
+redef class Float
+	# Sleep approximately `self` seconds
+	fun sleep `{
+		time_t s = self;
+		long ns = (self-s) * 1000000000.0;
+		const struct timespec req = {s, ns};
+		nanosleep(&req, NULL);
+	`}
+end
+
 # Time since epoch
 extern class TimeT `{time_t`}
 

lib/gamnit/limit_fps.nit

@@ -0,0 +1,78 @@
+# 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 limit_fps
+
+import gamnit
+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 = 60.0 is writable
+
+	# Current frame-rate
+	#
+	# Updated each 5 seconds.
+	var current_fps = 0.0
+
+	redef fun frame_full
+	do
+		super
+		limit_fps
+	end
+
+	# The clock for limit_fps
+	private var clock = new Clock
+
+	# Number of frames since the last deadline
+	#
+	# Used to compute `current_fps`.
+	private var frame_count = 0
+
+	# Deadline used to compute `current_fps`
+	private var frame_count_deadline = 0
+
+	# Check and sleep to maintain a frame-rate bellow `maximum_fps`
+	#
+	# Also periodically update `current_fps`
+	# Is automatically called at the end of `full_frame`.
+	fun limit_fps
+	do
+		var t = clock.total.sec
+		if t >= frame_count_deadline then
+			var cfps = frame_count.to_f / 5.0
+			self.current_fps = cfps
+			frame_count = 0
+			frame_count_deadline = t + 5
+		end
+		frame_count += 1
+
+		var mfps = maximum_fps
+		if mfps <= 0.0 then return
+		var lapse = clock.lapse
+		var dt = lapse.to_f
+		var target_dt = 1.0 / mfps
+		if dt < target_dt then
+			var sleep_t = target_dt - dt
+			sleep_t.sleep
+			clock.lapse
+		end
+	end
+end

lib/mnit/mnit_fps.nit

@@ -24,7 +24,7 @@ redef class App
 	# Zero (or a negative value) means no limit.
 	#
 	# Applications can modify this value even during the main-loop.
-	var maximum_fps = 60 is writable
+	var maximum_fps = 60.0 is writable
 
 	# Current frame-rate
 	# Updated each 5 seconds.
@@ -53,23 +53,22 @@ redef class App
 	do
 		var t = clock.total.sec
 		if t >= frame_count_deadline then
-			var cfps = frame_count_deadline.to_f / 5.0
+			var cfps = frame_count.to_f / 5.0
 			self.current_fps = cfps
 			frame_count = 0
 			frame_count_deadline = t + 5
 		end
 		frame_count += 1
 
 		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
+		if mfps <= 0.0 then return
+		var lapse = clock.lapse
+		var dt = lapse.to_f
+		var target_dt = 1.0 / mfps
+		if dt < target_dt then
+			var sleep_t = target_dt - dt
+			sleep_t.sleep
+			clock.lapse
 		end
 	end
 end