Write dynamic linking platform shim for Windows

Last ditch effort to at least kind of support Windows natively. I'm not
even going to try to port the networking code, because Windows doesn't
even support berkeley sockets, as far as I know.

src/utils/platform/dyn.c

@@ -0,0 +1,30 @@
+#ifdef WINDOWS
+#include <libloaderapi.h>
+#else
+#include <dlfcn.h>
+#endif
+#include "dyn.h"
+
+void *dyn_load(const char *filename) {
+#ifdef WINDOWS
+	return (void *)LoadLibraryA(filename);
+#else
+	return dlopen(filename, RTLD_LAZY);
+#endif
+}
+
+void *dyn_sym(void *handle, const char *name) {
+#ifdef WINDOWS
+	return (void *)GetProcAddress((HMODULE)handle, name);
+#else
+	return dlsym(handle, name);
+#endif
+}
+
+int dyn_close(void *handle) {
+#ifdef WINDOWS
+	return (int)FreeLibrary((HMODULE)handle);
+#else
+	return dlclose(handle);
+#endif
+}

src/utils/platform/dyn.h

@@ -0,0 +1,8 @@
+#ifndef _DYN_H
+#define _DYN_H
+
+void *dyn_load(const char *filename);
+void *dyn_sym(void *handle, const char *name);
+int dyn_close(void *handle);
+
+#endif

src/utils/ui.c

@@ -21,8 +21,7 @@
 #include "logo.h"
 #include "loaders/textureloader.h"
 #include "args.h"
-
-#include <dlfcn.h>
+#include "platform/dyn.h"
 
 #include "../vendored/SDL2/SDL_render.h"
 #include "../vendored/SDL2/SDL_events.h"
@@ -71,11 +70,12 @@ struct sdl_syms {
 static void *try_find_sdl2_lib(void) {
 	char *candidates[] = {
 		"libSDL2-2.0.so",
-		"libSDL2-2.0.0.dylib"
+		"libSDL2-2.0.0.dylib",
+		"SDL2.dll"
 	};
 	void *lib = NULL;
 	for (size_t i = 0; i < (sizeof(candidates) / sizeof(*candidates)); ++i) {
-		if ((lib = dlopen(candidates[i], RTLD_LAZY))) return lib;
+		if ((lib = dyn_load(candidates[i]))) return lib;
 	}
 
 	logr(info, "Couldn't find SDL library, tried the following names: ");
@@ -93,27 +93,27 @@ static struct sdl_syms *try_get_sdl2_syms(void) {
 	struct sdl_syms *syms = calloc(1, sizeof(*syms));
 	*syms = (struct sdl_syms){
 		.lib = sdl2,
-		.SDL_VideoInit              = dlsym(sdl2, "SDL_VideoInit"),
-		.SDL_VideoQuit              = dlsym(sdl2, "SDL_VideoQuit"),
-		.SDL_Quit                   = dlsym(sdl2, "SDL_Quit"),
-		.SDL_GetError               = dlsym(sdl2, "SDL_GetError"),
-		.SDL_SetWindowIcon          = dlsym(sdl2, "SDL_SetWindowIcon"),
-		.SDL_FreeSurface            = dlsym(sdl2, "SDL_FreeSurface"),
-		.SDL_CreateRGBSurfaceFrom   = dlsym(sdl2, "SDL_CreateRGBSurfaceFrom"),
-		.SDL_CreateWindow           = dlsym(sdl2, "SDL_CreateWindow"),
-		.SDL_CreateRenderer         = dlsym(sdl2, "SDL_CreateRenderer"),
-		.SDL_CreateTexture          = dlsym(sdl2, "SDL_CreateTexture"),
-		.SDL_DestroyTexture         = dlsym(sdl2, "SDL_DestroyTexture"),
-		.SDL_DestroyRenderer        = dlsym(sdl2, "SDL_DestroyRenderer"),
-		.SDL_DestroyWindow          = dlsym(sdl2, "SDL_DestroyWindow"),
-		.SDL_RenderPresent          = dlsym(sdl2, "SDL_RenderPresent"),
-		.SDL_RenderSetLogicalSize   = dlsym(sdl2, "SDL_RenderSetLogicalSize"),
-		.SDL_SetRenderDrawBlendMode = dlsym(sdl2, "SDL_SetRenderDrawBlendMode"),
-		.SDL_SetTextureBlendMode    = dlsym(sdl2, "SDL_SetTextureBlendMode"),
-		.SDL_RenderSetScale         = dlsym(sdl2, "SDL_RenderSetScale"),
-		.SDL_PollEvent              = dlsym(sdl2, "SDL_PollEvent"),
-		.SDL_UpdateTexture          = dlsym(sdl2, "SDL_UpdateTexture"),
-		.SDL_RenderCopy             = dlsym(sdl2, "SDL_RenderCopy")
+		.SDL_VideoInit              = dyn_sym(sdl2, "SDL_VideoInit"),
+		.SDL_VideoQuit              = dyn_sym(sdl2, "SDL_VideoQuit"),
+		.SDL_Quit                   = dyn_sym(sdl2, "SDL_Quit"),
+		.SDL_GetError               = dyn_sym(sdl2, "SDL_GetError"),
+		.SDL_SetWindowIcon          = dyn_sym(sdl2, "SDL_SetWindowIcon"),
+		.SDL_FreeSurface            = dyn_sym(sdl2, "SDL_FreeSurface"),
+		.SDL_CreateRGBSurfaceFrom   = dyn_sym(sdl2, "SDL_CreateRGBSurfaceFrom"),
+		.SDL_CreateWindow           = dyn_sym(sdl2, "SDL_CreateWindow"),
+		.SDL_CreateRenderer         = dyn_sym(sdl2, "SDL_CreateRenderer"),
+		.SDL_CreateTexture          = dyn_sym(sdl2, "SDL_CreateTexture"),
+		.SDL_DestroyTexture         = dyn_sym(sdl2, "SDL_DestroyTexture"),
+		.SDL_DestroyRenderer        = dyn_sym(sdl2, "SDL_DestroyRenderer"),
+		.SDL_DestroyWindow          = dyn_sym(sdl2, "SDL_DestroyWindow"),
+		.SDL_RenderPresent          = dyn_sym(sdl2, "SDL_RenderPresent"),
+		.SDL_RenderSetLogicalSize   = dyn_sym(sdl2, "SDL_RenderSetLogicalSize"),
+		.SDL_SetRenderDrawBlendMode = dyn_sym(sdl2, "SDL_SetRenderDrawBlendMode"),
+		.SDL_SetTextureBlendMode    = dyn_sym(sdl2, "SDL_SetTextureBlendMode"),
+		.SDL_RenderSetScale         = dyn_sym(sdl2, "SDL_RenderSetScale"),
+		.SDL_PollEvent              = dyn_sym(sdl2, "SDL_PollEvent"),
+		.SDL_UpdateTexture          = dyn_sym(sdl2, "SDL_UpdateTexture"),
+		.SDL_RenderCopy             = dyn_sym(sdl2, "SDL_RenderCopy")
 	};
 	for (size_t i = 0; i < (sizeof(struct sdl_syms) / sizeof(void *)); ++i) {
 		if (!((void **)syms)[i]) {
@@ -275,7 +275,7 @@ void win_destroy(struct sdl_window *w) {
 			w->sym->SDL_DestroyWindow(w->window);
 			w->window = NULL;
 		}
-		dlclose(w->sym->lib);
+		dyn_close(w->sym->lib);
 		free(w->sym);
 	}
 	free(w);