add webgl support

src/asset.cpp

@@ -145,6 +145,8 @@ bool Asset::create_dir(const std::string& path)
     return android_create_dir(path);
 #elif __IOS__ || __OSX__
     return apple_create_dir(path);
+else
+    return false;
 #endif
 }
 
@@ -155,6 +157,7 @@ static size_t curl_data_handler_asset(void* contents, size_t size, size_t nmemb,
     return size * nmemb;
 }
 
+#if WITH_CURL
 static int progress_callback_asset_download(void* clientp, curl_off_t dltotal,
     curl_off_t dlnow, curl_off_t ultotal, curl_off_t ulnow)
 {
@@ -168,9 +171,11 @@ static int progress_callback_asset_download(void* clientp, curl_off_t dltotal,
     bool cont = ass->on_progress(p);
     return cont ? 0 : 1;
 }
+#endif //CURL
 
 bool Asset::open_url(const std::string& url, std::function<bool(float)> progress /*= nullptr*/)
 {
+#if WITH_CURL
     CURL* curl = curl_easy_init();
     if (curl)
     {
@@ -204,6 +209,7 @@ bool Asset::open_url(const std::string& url, std::function<bool(float)> progress
             return true;
         }
     }
+#endif // CURL
     return false;
 }