move opengl library loading to a thread that starts as soon as possible and is awaited as late as we can allow

src/twn_engine_context_c.h

@@ -28,6 +28,7 @@ typedef struct EngineContext {
     char **argv;
     /* where the app was run from, used as the root for packs */
     char *base_dir;
+    char *title;
 
     Vec2 window_dims;
     Rect viewport_rect;

src/twn_loop.c

@@ -4,7 +4,6 @@
 #include "twn_util.h"
 #include "twn_util_c.h"
 #include "twn_game_object_c.h"
-#include "twn_audio_c.h"
 #include "twn_textures_c.h"
 
 #include <SDL2/SDL.h>
@@ -20,6 +19,9 @@
 #define PACKAGE_EXTENSION "btw"
 
 
+static SDL_Thread *opengl_load_thread;
+
+
 static int event_callback(void *userdata, SDL_Event *event) {
     (void)userdata;
 
@@ -342,14 +344,16 @@ ERR_PACK_MANIFEST_PATH_ALLOC_FAIL:
 }
 
 
-static bool initialize(void) {
+static int opengl_load_thread_fn(void *data) {
-    profile_start("SDL initialization");
+    (void)data;
-    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_EVENTS) == -1) {
-        CRY_SDL("SDL initialization failed.");
-        return false;
-    }
-    profile_end("SDL initialization");
 
+    SDL_GL_LoadLibrary(NULL);
+
+    return 0;
+}
+
+
+static bool initialize(void) {
     /* first things first, most things here will be loaded from the config file */
     /* it's expected to be present in the data directory, no matter what */
     /* that is why PhysicsFS is initialized before anything else */
@@ -446,11 +450,11 @@ static bool initialize(void) {
     SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER, 1);
     SDL_GL_SetAttribute(SDL_GL_ACCELERATED_VISUAL, 1);
 
-    /* init got far enough to create a window */
-    {
     toml_datum_t datum_title = toml_string_in(about, "title");
     if (!datum_title.ok)
-            datum_title.u.s = "townengine project";
+        datum_title.u.s = SDL_strdup("townengine project");
+
+    ctx.title = datum_title.u.s;
 
     /* not yet used
     toml_datum_t datum_developer = toml_string_in(about, "developer");
@@ -485,52 +489,7 @@ static bool initialize(void) {
     ctx.game.resolution.x = (float)ctx.base_render_width;
     ctx.game.resolution.y = (float)ctx.base_render_height;
 
-        /* TODO: investigate viability of detached thread driver and window creation, as it's the worst load time offender */
-        profile_start("window creation");
-        ctx.window = SDL_CreateWindow(datum_title.u.s,
-                                      SDL_WINDOWPOS_CENTERED,
-                                      SDL_WINDOWPOS_CENTERED,
-                                      (int)ctx.base_render_width,
-                                      (int)ctx.base_render_height,
-                                      //SDL_WINDOW_ALLOW_HIGHDPI |
-                                          SDL_WINDOW_RESIZABLE |
-                                          SDL_WINDOW_OPENGL);
-        profile_end("window creation");
-
-        if (datum_title.ok)
-            SDL_free(datum_title.u.s);
-
     //SDL_free(datum_developer.u.s);
-    }
-
-    if (ctx.window == NULL) {
-        CRY_SDL("Window creation failed.");
-        goto fail;
-    }
-
-    profile_start("opengl context creation");
-    ctx.gl_context = SDL_GL_CreateContext(ctx.window);
-    if (!ctx.gl_context) {
-        CRY_SDL("GL context creation failed.");
-        goto fail;
-    }
-
-    if (SDL_GL_MakeCurrent(ctx.window, ctx.gl_context)) {
-        CRY_SDL("GL context binding failed.");
-        goto fail;
-    }
-
-    /* TODO: figure out what we ultimately prefer */
-    SDL_GL_SetSwapInterval(0);
-
-    if (!render_init())
-        goto fail;
-
-    setup_viewport(0, 0, (int)ctx.base_render_width, (int)ctx.base_render_height);
-    profile_end("opengl context creation");
-
-    /* might need this to have multiple windows */
-    ctx.window_id = SDL_GetWindowID(ctx.window);
 
     /* TODO: */
     // SDL_GetRendererOutputSize(ctx.renderer, &ctx.window_w, &ctx.window_h);
@@ -628,11 +587,6 @@ static bool initialize(void) {
     ctx.render_queue_2d = NULL;
     ctx.uncolored_mesh_batches = NULL;
 
-    profile_start("texture and text cache initialization");
-    textures_cache_init(&ctx.texture_cache, ctx.window);
-    text_cache_init(&ctx.text_cache);
-    profile_end("texture and text cache initialization");
-
     /* input */
     toml_datum_t datum_keybind_slots = toml_int_in(engine, "keybind_slots");
     if (!datum_keybind_slots.ok) {
@@ -652,6 +606,63 @@ static bool initialize(void) {
     ctx.game.fog_color = (Color){ 255, 255, 255, 255 }; /* TODO: pick some grey? */
     ctx.game.fog_end = 1.0f;
 
+    update_viewport();
+
+    profile_start("game object load");
+    /* now we can actually start doing stuff */
+    game_object_load();
+    profile_end("game object load");
+
+    /* delayed as further as possible so that more work is done before we have to wait */
+    SDL_WaitThread(opengl_load_thread, NULL);
+    profile_end("opengl loading");
+
+    /* TODO: investigate viability of detached thread driver and window creation, as it's the worst load time offender */
+    profile_start("window creation");
+    ctx.window = SDL_CreateWindow(ctx.title,
+                                  SDL_WINDOWPOS_CENTERED,
+                                  SDL_WINDOWPOS_CENTERED,
+                                  (int)ctx.base_render_width,
+                                  (int)ctx.base_render_height,
+                                  //SDL_WINDOW_ALLOW_HIGHDPI |
+                                      SDL_WINDOW_RESIZABLE |
+                                      SDL_WINDOW_OPENGL);
+    profile_end("window creation");
+
+    if (ctx.window == NULL) {
+        CRY_SDL("Window creation failed.");
+        goto fail;
+    }
+
+    profile_start("opengl context creation");
+    ctx.gl_context = SDL_GL_CreateContext(ctx.window);
+    if (!ctx.gl_context) {
+        CRY_SDL("GL context creation failed.");
+        goto fail;
+    }
+
+    if (SDL_GL_MakeCurrent(ctx.window, ctx.gl_context)) {
+        CRY_SDL("GL context binding failed.");
+        goto fail;
+    }
+
+    /* TODO: figure out what we ultimately prefer */
+    SDL_GL_SetSwapInterval(0);
+
+    if (!render_init())
+        goto fail;
+
+    setup_viewport(0, 0, (int)ctx.base_render_width, (int)ctx.base_render_height);
+    profile_end("opengl context creation");
+
+    /* might need this to have multiple windows */
+    ctx.window_id = SDL_GetWindowID(ctx.window);
+
+    profile_start("texture and text cache initialization");
+    textures_cache_init(&ctx.texture_cache, ctx.window);
+    text_cache_init(&ctx.text_cache);
+    profile_end("texture and text cache initialization");
+
     return true;
 
 fail:
@@ -674,7 +685,9 @@ static void clean_up(void) {
     PHYSFS_deinit();
 
     SDL_free(ctx.base_dir);
+    SDL_free(ctx.title);
     SDL_GL_DeleteContext(ctx.gl_context);
+    SDL_GL_UnloadLibrary();
     SDL_Quit();
 }
 
@@ -688,6 +701,20 @@ static void reset_state(void) {
 int enter_loop(int argc, char **argv) {
     profile_start("startup");
 
+    profile_start("SDL initialization");
+    if (SDL_Init(SDL_INIT_VIDEO | SDL_INIT_AUDIO | SDL_INIT_EVENTS) == -1) {
+        CRY_SDL("SDL initialization failed.");
+        return EXIT_FAILURE;
+    }
+    profile_end("SDL initialization");
+
+    profile_start("opengl loading");
+    opengl_load_thread = SDL_CreateThread(opengl_load_thread_fn, "opengl loader", NULL);
+    if (!opengl_load_thread) {
+        CRY_SDL("Cannot create opengl loading thread: ");
+        return EXIT_FAILURE;
+    }
+
     ctx.argc = argc;
     ctx.argv = argv;
     ctx.base_dir = SDL_GetBasePath();
@@ -763,13 +790,6 @@ int enter_loop(int argc, char **argv) {
         ctx.game.debug = false;
     }
 
-    update_viewport();
-
-    profile_start("game object load");
-    /* now we can actually start doing stuff */
-    game_object_load();
-    profile_end("game object load");
-
     ctx.was_successful = true;
     ctx.game.initialization_needed = true;