From b14d2f292a357f8491146a03e695b6418bc3433b Mon Sep 17 00:00:00 2001
From: Camden Dixie O'Brien <cdo@wip.sh>
Date: Thu, 2 Jan 2025 01:16:37 +0000
Subject: [PATCH] Create basic engine

---
 engine/CMakeLists.txt         |  4 +--
 engine/engine.c               | 66 +++++++++++++++++++++++++++++++++++
 engine/foo.c                  | 11 ------
 engine/include/engine_hooks.h | 34 ++++++++++++++++++
 engine/include/foo.h          | 11 ------
 5 files changed, 101 insertions(+), 25 deletions(-)
 create mode 100644 engine/engine.c
 delete mode 100644 engine/foo.c
 create mode 100644 engine/include/engine_hooks.h
 delete mode 100644 engine/include/foo.h

diff --git a/engine/CMakeLists.txt b/engine/CMakeLists.txt
index fdfb906..dc63058 100644
--- a/engine/CMakeLists.txt
+++ b/engine/CMakeLists.txt
@@ -1,5 +1,3 @@
-add_library(engine
-  foo.c
-)
+add_library(engine engine.c)
 set_default_target_options(engine)
 target_include_directories(engine PUBLIC include)
diff --git a/engine/engine.c b/engine/engine.c
new file mode 100644
index 0000000..b9c7395
--- /dev/null
+++ b/engine/engine.c
@@ -0,0 +1,66 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#include "engine_hooks.h"
+
+#include <assert.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <stdlib.h>
+
+#define FRAMERATE 60
+#define INTERVAL (1000 / FRAMERATE)
+
+int main(int argc, char *argv[])
+{
+	int err = SDL_Init(SDL_INIT_VIDEO);
+	assert(0 == err);
+
+	SDL_Window *window = SDL_CreateWindow(
+	    game_conf.win.title, SDL_WINDOWPOS_UNDEFINED,
+	    SDL_WINDOWPOS_UNDEFINED, game_conf.win.w, game_conf.win.h, 0);
+	assert(NULL != window);
+
+	SDL_Renderer *renderer = SDL_CreateRenderer(window, -1, 0);
+	assert(NULL != renderer);
+
+	void *gamemem = calloc(1, game_conf.memsize);
+	game_init(argc, argv, gamemem, renderer);
+
+	uint64_t prevt = SDL_GetTicks64();
+	while (1) {
+		uint64_t t = SDL_GetTicks64();
+		uint64_t dt = t - prevt;
+
+		if (dt >= INTERVAL) {
+			// Handle all events currently in queue
+			SDL_Event evt;
+			while (SDL_PollEvent(&evt)) {
+				if (game_evthandle(gamemem, &evt) != GAMESTATUS_OK)
+					goto quit;
+			}
+
+			// Update game state
+			if (game_update(gamemem, dt) != GAMESTATUS_OK)
+				goto quit;
+
+			// Render frame
+			SDL_RenderClear(renderer);
+			game_render(gamemem, renderer, t);
+			SDL_RenderPresent(renderer);
+
+			// Set previous frame draw time
+			prevt = t;
+		}
+
+		SDL_Delay(2);
+	}
+
+quit:
+	game_teardown(gamemem);
+	SDL_DestroyRenderer(renderer);
+	SDL_DestroyWindow(window);
+	SDL_Quit();
+}
diff --git a/engine/foo.c b/engine/foo.c
deleted file mode 100644
index d8aa547..0000000
--- a/engine/foo.c
+++ /dev/null
@@ -1,11 +0,0 @@
-/*
- * Copyright (c) Camden Dixie O'Brien
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-#include "foo.h"
-
-int foo(void)
-{
-	return 42;
-}
diff --git a/engine/include/engine_hooks.h b/engine/include/engine_hooks.h
new file mode 100644
index 0000000..3442809
--- /dev/null
+++ b/engine/include/engine_hooks.h
@@ -0,0 +1,34 @@
+/*
+ * Copyright (c) Camden Dixie O'Brien
+ * SPDX-License-Identifier: AGPL-3.0-only
+ */
+
+#ifndef ENGINE_HOOKS_H
+#define ENGINE_HOOKS_H
+
+#include <SDL2/SDL.h>
+
+typedef struct {
+	struct {
+		const char *title;
+		unsigned w, h;
+	} win;
+	size_t memsize;
+} engineconf_t;
+
+typedef enum {
+	GAMESTATUS_OK,
+	GAMESTATUS_QUIT,
+} gamestatus_t;
+
+extern const engineconf_t game_conf;
+
+void game_init(int argc, char *argv[], void *mem, SDL_Renderer *renderer);
+void game_teardown(void *mem);
+
+gamestatus_t game_evthandle(void *mem, const SDL_Event *evt);
+gamestatus_t game_update(void *mem, unsigned dt);
+
+void game_render(const void *mem, SDL_Renderer *renderer, long unsigned t);
+
+#endif
diff --git a/engine/include/foo.h b/engine/include/foo.h
deleted file mode 100644
index 271ad16..0000000
--- a/engine/include/foo.h
+++ /dev/null
@@ -1,11 +0,0 @@
-/*
- * Copyright (c) Camden Dixie O'Brien
- * SPDX-License-Identifier: AGPL-3.0-only
- */
-
-#ifndef FOO_H
-#define FOO_H
-
-int foo(void);
-
-#endif