make textures_dump_atlases work again and expose it as a utility function

src/twn_util.c

@@ -165,6 +165,30 @@ char *file_to_str(const char *path) {
 }
 
 
+void textures_dump_atlases(void) {
+    PHYSFS_mkdir("/dump");
+
+    /* TODO: png instead of bmp */
+    const char string_template[] = "/dump/atlas%zd.bmp";
+
+    size_t i = 0;
+    for (; i < arrlenu(ctx.texture_cache.atlas_surfaces); ++i) {
+        char *buf = NULL;
+        SDL_asprintf(&buf, string_template, i);
+
+        SDL_RWops *handle = PHYSFSRWOPS_openWrite(buf);
+
+        if (handle == NULL) {
+            CRY("Texture atlas dump failed.", "File could not be opened");
+            return;
+        }
+
+        SDL_SaveBMP_RW(ctx.texture_cache.atlas_surfaces[i], handle, true);
+        log_info("Dumped atlas %zu to %s", i, buf);
+    }
+}
+
+
 bool strends(const char *str, const char *suffix) {
     size_t str_length = SDL_strlen(str);
     size_t suffix_length = SDL_strlen(suffix);