ContentVerification class

A standalone content verification system for WebF that checks if actual content has been rendered instead of a blank screen. This can be used by applications to verify content visibility before taking screenshots, running tests, or reporting custom metrics.

Example usage:

final controller = WebFController(...);
// ... after page loads ...

if (ContentVerification.hasVisibleContent(controller)) {
  print('Page has visible content');
} else {
  print('Page appears to be blank');
}

// Get detailed information
final info = ContentVerification.getContentInfo(controller);
print('Visible elements: ${info.totalElements}');
print('Text elements: ${info.textElements}');