I use Electron and (any) html+css combination I can imagine / download. You can do the core in freepascal and -try to- link it (.dll / .exe) against the electron app with JavaScript.
Do you have a screenshot of the UI of an app you designed this way?
Thanks!
Not now, since I didn't need pascal for such a simple application. But I have this one attached, using Material Design Lite with little modifications. The source code is on my github page, so you can grab the code for running an external application, changing it a bit the output is redirected to the electron application where you can do anything with it (I can imagine a communication with files, you create a file with the data with electron and pass the filename to the pascal application, then the pascal returns in the command line a JSON that you can use). Another way is using a database with electron and process with fpc when needed. So a command line utility will be the case I can do.
Maybe a dll is harder to do, at least I found only for C++ and C# .dll's tutorials to use them with Electron. You will need a header for data-types between electron and fpc.
Edit: I choose Material Design Lite, you can use Angular Material, Bootstrap or buy a theme somewhere.