From 80df1ee771b1e334693ada728c6563193da6f6a4 Mon Sep 17 00:00:00 2001
From: Varun Patil <radialapps@gmail.com>
Date: Thu, 7 May 2020 00:51:18 +0530
Subject: [PATCH] Add back main update loop with framerate limit

---
 binding-mruby/binding-mruby.cpp | 60 +++++++++++++++++++++++++++++++++
 shell.html                      |  2 +-
 src/config.cpp                  |  3 +-
 src/main.cpp                    |  4 +++
 4 files changed, 67 insertions(+), 2 deletions(-)

diff --git a/binding-mruby/binding-mruby.cpp b/binding-mruby/binding-mruby.cpp
index 7cb0b64..52f88c6 100644
--- a/binding-mruby/binding-mruby.cpp
+++ b/binding-mruby/binding-mruby.cpp
@@ -52,6 +52,10 @@
 
 #include <stdio.h>
 
+#ifdef __EMSCRIPTEN__
+#include <emscripten.h>
+#endif
+
 static void mrbBindingExecute();
 static void mrbBindingTerminate();
 static void mrbBindingReset();
@@ -244,6 +248,57 @@ runMrbFile(mrb_state *mrb, const char *filename)
 	fclose(f);
 }
 
+mrb_state * static_mrb;
+
+#ifdef __EMSCRIPTEN__
+EM_JS(int, jsSkipFrame, (), {
+	// Initialize
+	const targetRate = window.skfTargetFrameRate || 40;
+	if (!window.skfFrameTimings) {
+		window.skfFrameTimings = [];
+		window.skfPreviousRate = targetRate;
+	}
+
+	// Get current time
+	const ctime = performance.now();
+
+	// Wait till we have n elements
+	if (window.skfFrameTimings.length < (window.skfNumFrames || 8)) {
+		window.skfFrameTimings.push(ctime);
+		return 0;
+	}
+
+	// Get average framerate
+	const framerate = 1000 / ((ctime - window.skfFrameTimings[0]) / window.skfFrameTimings.length);
+
+	// Proportional error
+	const Pe = framerate - targetRate;
+
+	// Derivative error
+	const De = (window.skfPreviousRate - framerate);
+
+	// Set previous rate
+	window.skfPreviousRate = framerate;
+
+	// Drop frame if necessary
+	if (Pe - De - 1 > 0) {
+		return 1;
+	}
+
+	// Add the timing
+	window.skfFrameTimings.shift();
+	window.skfFrameTimings.push(ctime);
+	return 0;
+});
+#endif
+
+void main_update_loop() {
+#ifdef __EMSCRIPTEN__
+	if (jsSkipFrame() == 1) return;
+#endif
+	mrb_load_nstring_cxt(static_mrb, "main_update_loop", 16, NULL);
+}
+
 static void
 runRMXPScripts(mrb_state *mrb, mrbc_context *ctx)
 {
@@ -368,6 +423,11 @@ runRMXPScripts(mrb_state *mrb, mrbc_context *ctx)
 		}
 	}
 
+#ifdef __EMSCRIPTEN__
+	static_mrb = mrb;
+	emscripten_set_main_loop(main_update_loop, 0, true);
+#endif
+
 	mrb_close(scriptMrb);
 }
 
diff --git a/shell.html b/shell.html
index 7bb360c..e32ed46 100644
--- a/shell.html
+++ b/shell.html
@@ -171,7 +171,7 @@
       }
 
       window.onerror = function() {
-          alert("An error occured!")
+          console.error("An error occured!")
       };
 
       window.fileLoadedAsync = function(file) {
diff --git a/src/config.cpp b/src/config.cpp
index a782f61..f7f5f6e 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -191,7 +191,7 @@ void Config::read(int argc, char *argv[])
 
 	PO_DESC_ALL;
 	gameFolder = "game";
-	fixedFramerate = 40;
+	fixedFramerate = -1;
 	syncToRefreshrate = false;
 	rgssVersion = 1;
 	defScreenW = 640;
@@ -199,6 +199,7 @@ void Config::read(int argc, char *argv[])
 	enableBlitting = false;
 	winResizable = false;
 	windowTitle = "KN_E";
+	frameSkip = false;
 
 #undef PO_DESC
 #undef PO_DESC_ALL
diff --git a/src/main.cpp b/src/main.cpp
index 59cde9d..c7ff82a 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -159,6 +159,10 @@ int rgssThreadFun(void *userdata)
 	/* Start script execution */
 	scriptBinding->execute();
 
+#ifdef __EMSCRIPTEN
+	return 0;
+#endif
+
 	threadData->rqTermAck.set();
 	threadData->ethread->requestTerminate();