I have a image loading problem on GWT.

On server side:

• I have a HttpServlet that creates and transfers Captcha images using "

  How should I debug it? Please help.

  tbCaptcha = new TextBox();
  
  imgCaptcha = new Image();
  imgCaptcha.addErrorHandler(new ErrorHandler() {
      public void one rror(ErrorEvent event) {
          d.ce("onCaptcha", "onError", System.currentTimeMillis());
          onCaptcha.execute();
      }
  });
  imgCaptcha.addLoadHandler(new LoadHandler() {
      public void onl oad(LoadEvent event) {
          d.cr("onCaptcha", "onLoad", System.currentTimeMillis());
      }
  });
  
  var login = TGS_LibScaleServletUtils.login();
  var newUrl = TGC_CaptchaUtils.newUrl(login.domain, login.port, login.spi);
  imgCaptcha.setUrl(newUrl);
  

  And yes, I am creating a new URL with a random parameter and using Image.prefetch as below:

  public static String newUrl(CharSequence domain, Integer port, CharSequence spi) {
      var newUrlCaptcha = TGS_UrlBuilderUtils.https()
              .domain(domain).port(port).directory(spi)
              .fileOrServlet(TGS_SURLUtils.LOC_NAME)
              .parameter(TGS_SURLUtils.PARAM_NAME, TGS_CaptchaUtils.SERVLET_REFRESH())
              .parameterRandom("r", 10).toString();
      Image.prefetch(newUrlCaptcha);
      return newUrlCaptcha;
  }
  

  Client side console:

  

  CodePudding user response：

  Change to Light browser theme from Dark Dark Theme. As captcha image is transparent having black colored text, which matches with black background.