THPDFCSCSignatureProvider.EstimateSignatureSize Method
function EstimateSignatureSize(
const Request: THPDFSignatureProviderRequest;
out SignatureBytes: Integer): THPDFSignatureProviderStatus;
override;Reports the signature placeholder size in bytes to reserve for this credential before signing
The configured THPDFCSCOptions.EstimatedSignatureBytes wins when it is positive, so deployments that know their provider's exact signature size can pin the placeholder
Without an explicit estimate, RSA credentials (hsaRSAPKCS1v15 and hsaRSAPSS) derive the size as (KeyBits+7) div 8 from the cached credential info when it fits MaxSignatureBytes
The method returns spsValid with a positive estimate, or spsUnsupported with zero when neither the configuration nor the credential metadata yields a size, for example for EC credentials without an explicit estimate