Started on the engine proper

core/engine.c

@@ -0,0 +1,113 @@
+#include "engine.h"
+
+#include <stdio.h>
+
+//errors here should be fatal
+static void error(Engine* engine, char* message) {
+	fprintf(stderr, message);
+	exit(-1);
+}
+
+//exposed functions
+void initEngine(Engine* engine) {
+	//clear
+	engine->root = NULL;
+	engine->running = true;
+
+	//init SDL
+	if (SDL_Init(0) != 0) {
+		error(engine, "Failed to initialize SDL2");
+	}
+
+	//init the window
+	engine->window = SDL_CreateWindow(
+		"Caption",
+		SDL_WINDOWPOS_UNDEFINED,
+		SDL_WINDOWPOS_UNDEFINED,
+		engine->screenWidth,
+		engine->screenHeight,
+		SDL_WINDOW_RESIZABLE
+	);
+
+	if (engine->window == NULL) {
+		error(engine, "Failed to initialize the window");
+	}
+
+	//init the renderer
+	engine->renderer = SDL_CreateRenderer(engine->window, -1, 0);
+
+	if (engine->renderer == NULL) {
+		error(engine, "Failed to initialize the renderer");
+	}
+
+	SDL_SetHint(SDL_HINT_RENDER_SCALE_QUALITY, "best");
+	SDL_RenderSetLogicalSize(engine->renderer, engine->screenWidth, engine->screenHeight);
+}
+
+void freeEngine(Engine* engine) {
+	SDL_DestroyRenderer(engine->renderer);
+	SDL_DestroyWindow(engine->window);
+	SDL_Quit();
+
+	engine->renderer = NULL;
+	engine->window = NULL;
+}
+
+static void execStep(Engine* engine) {
+	//DEBUG: for now, just poll events
+	SDL_Event event;
+	while (SDL_PollEvent(&event)) {
+		switch(event.type) {
+			//quit
+			case SDL_QUIT: {
+				engine->running = false;
+			}
+			break;
+
+			//window events are handled internally
+			case SDL_WINDOWEVENT: {
+				switch(event.window.event) {
+					case SDL_WINDOWEVENT_RESIZED:
+						SDL_RenderSetLogicalSize(engine->renderer, event.window.data1, event.window.data2);
+					break;
+				}
+			}
+			break;
+
+			//TODO: input
+		}
+	}
+}
+
+//the heart of the engine
+void execEngine(Engine* engine) {
+	//set up time
+	gettimeofday(&engine->realTime, NULL);
+	engine->simTime = engine->realTime;
+	struct timeval delta = { .tv_sec = 0, .tv_usec = 1000 * 1000 / 60 }; //60 frames per second
+
+	while (engine->running) {
+		//calc the time passed
+		gettimeofday(&engine->realTime, NULL);
+
+		//if not enough time has passed
+		if (engine->simTime.tv_sec < engine->realTime.tv_sec && engine->simTime.tv_usec < engine->realTime.tv_usec) {
+			//while not enough time has passed
+			while(engine->simTime.tv_sec < engine->realTime.tv_sec && engine->simTime.tv_usec < engine->realTime.tv_usec) {
+				//simulate the world
+				execStep(engine);
+
+				//calc the time simulation
+				timeradd(&delta, &engine->simTime, &engine->simTime);
+			}
+		}
+		else {
+			SDL_Delay(10); //let the machine sleep, 10ms
+		}
+
+		//render the world
+		SDL_SetRenderDrawColor(engine->renderer, 0, 0, 0, 255); //NOTE: This line can be disabled later
+		SDL_RenderClear(engine->renderer); //NOTE: This line can be disabled later
+		SDL_RenderPresent(engine->renderer);
+	}
+}