From 58488f8eabcc61089e0ae4297f38f10cc28d78c7 Mon Sep 17 00:00:00 2001
From: Matthew Kosarek <mattkae@protonmail.com>
Date: Sat, 27 Mar 2021 11:49:56 -0400
Subject: Working reusable simulation loop

---
 frontend/shared_cpp/MainLoop.cpp             | 30 ++++++++++++++++++++++++++++
 frontend/shared_cpp/MainLoop.h               | 29 +++++++++++++++++++++++++++
 frontend/shared_cpp/OrthographicRenderer.cpp |  2 ++
 frontend/shared_cpp/WebglContext.h           | 10 +++++++---
 4 files changed, 68 insertions(+), 3 deletions(-)
 create mode 100644 frontend/shared_cpp/MainLoop.cpp
 create mode 100644 frontend/shared_cpp/MainLoop.h

(limited to 'frontend/shared_cpp')

diff --git a/frontend/shared_cpp/MainLoop.cpp b/frontend/shared_cpp/MainLoop.cpp
new file mode 100644
index 0000000..82a24b5
--- /dev/null
+++ b/frontend/shared_cpp/MainLoop.cpp
@@ -0,0 +1,30 @@
+#include "MainLoop.h"
+#include <cstdio>
+#include <cstdlib>
+
+EM_BOOL loop(double time, void* loop) {
+    MainLoop* mainLoop = (MainLoop*) loop;
+    if (!mainLoop->isRunning) {
+        return false;
+    }
+    
+    if (mainLoop->lastTime == 0) {
+        mainLoop->lastTime = time;
+        return true;
+    }
+
+    long deltaTime = time - mainLoop->lastTime;
+    mainLoop->lastTime = time;
+    mainLoop->elapsedTime += deltaTime;
+    mainLoop->numFrames++;
+    float deltaTimeSeconds = static_cast<float>(deltaTime) / 1000.f;
+
+    if (mainLoop->elapsedTime >= 1000.0) {
+        printf("FPS: %d\n", mainLoop->numFrames);
+
+        mainLoop->elapsedTime = 0.0;
+        mainLoop->numFrames = 0;
+    }
+
+    return mainLoop->updateFunc(deltaTimeSeconds, NULL);
+}
\ No newline at end of file
diff --git a/frontend/shared_cpp/MainLoop.h b/frontend/shared_cpp/MainLoop.h
new file mode 100644
index 0000000..7300f6b
--- /dev/null
+++ b/frontend/shared_cpp/MainLoop.h
@@ -0,0 +1,29 @@
+#pragma once
+
+#include <emscripten.h>
+#include <emscripten/html5.h>
+#include <GLES2/gl2.h>
+#include <EGL/egl.h>
+
+EM_BOOL loop(double time, void* loop);
+
+struct MainLoop {
+    bool isRunning = false;
+	double lastTime = 0, elapsedTime = 0;
+	int numFrames = 0;
+	EM_BOOL (*updateFunc)(float dtSeconds, void *userData);
+
+    void run(EM_BOOL (*cb)(float dtSeconds, void *userData)) {
+		isRunning = true;
+		lastTime = 0;
+		elapsedTime = 0;
+		numFrames = 0;
+		updateFunc = cb;
+
+		emscripten_request_animation_frame_loop(loop, this);
+	}
+
+    void stop() {
+        isRunning = false;
+    }
+};
\ No newline at end of file
diff --git a/frontend/shared_cpp/OrthographicRenderer.cpp b/frontend/shared_cpp/OrthographicRenderer.cpp
index d160ecc..b6bd5b6 100644
--- a/frontend/shared_cpp/OrthographicRenderer.cpp
+++ b/frontend/shared_cpp/OrthographicRenderer.cpp
@@ -43,5 +43,7 @@ void OrthographicRenderer::render() {
 }
 
 void OrthographicRenderer::unload() {
+	glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
+    glClear(GL_COLOR_BUFFER_BIT);
 	glDeleteProgram(shader);
 }
diff --git a/frontend/shared_cpp/WebglContext.h b/frontend/shared_cpp/WebglContext.h
index c8a9480..1ea1c91 100644
--- a/frontend/shared_cpp/WebglContext.h
+++ b/frontend/shared_cpp/WebglContext.h
@@ -1,10 +1,13 @@
 #pragma once
+#include "types.h"
 #include <emscripten.h>
 #include <emscripten/html5.h>
 #include <GLES2/gl2.h>
 #include <EGL/egl.h>
 
 struct WebglContext {
+	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context;
+
 	void init(const char* query, int width = 640, int height = 480) {
 		emscripten_set_canvas_element_size( query, width, height);
 		
@@ -17,6 +20,9 @@ struct WebglContext {
 
 		context = emscripten_webgl_create_context(query, &attrs);
 		makeCurrentContext();
+
+		glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
+		glClear(GL_COLOR_BUFFER_BIT);	
 	};
 	
 	void makeCurrentContext() {
@@ -26,6 +32,4 @@ struct WebglContext {
 	void destroy() {
 		emscripten_webgl_destroy_context(context);
 	}
-
-	EMSCRIPTEN_WEBGL_CONTEXT_HANDLE context;
-};
+};
\ No newline at end of file
-- 
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