Restrictions in Functionality

Due to the fact that LyciaWeb is not a desktop client, but a web client, it has some limitations regarding 4GL functionality and form widgets:

• LyciaWeb cannot execute DDE functions, because there is no way a web application can affect other applications installed on the machine. For that same reason the built-in functions winshellexec() and winshelexecwait() cannot be used in applications run in LyciaWeb. They will be ignored, if present in the source code.

• • Browser widget will not function correctly and will not display the requested page, if the specified web site passes the X-Frame-Options in the header. If the DENY value is specified, any attempts to load the page in a frame fail, thus the browser widget will remain empty. If the SAMEORIGIN value is used, the browser widget will still display a web page, if this page is on the same site where the LyciaWeb application runs.

  • Browser widget, by default, will not display a site`s inner page with the ability to run scripts and submit forms. This is made for the security reasons as it may get information about sensitive data in 4GL application. To enable that back user may need to add TRUSTED class name into browser widget. On doing this the security restrictions will be disabled provided that there is no prohibition for opening the page in IFRAME tag on the site itself. Under this condition it can only be opened via additional reverse proxy because the Browser widget simply uses the IFRAME tag for running the page needed and does not depend on the browser version installed on the machine.

• Browsing a local machine from the Internet zone is forbidden in all modern browsers. This includes linking to files on your hard drive, on mapped network drives, and accessible via Uniform Naming Convention (UNC) paths. So if your form has an event which is aimed, for example, at opening the content of the C drive, it will not be processed and a corresponding message will be displayed.

Hot Keys Non-Supported

As LyciaWeb is a web client, it much depends on the limitations of a web browser an application is opened in. Among these restrictions are some hot-key combinations, that should not be used within the 4GL code.

The table below contains a number of available hot-key combinations, identifying whether they are supported or not by the most widely used browser types for the applications which LyciaWeb delivers to them.