Fpgui and lcl and qt, what are the advantages and disadvantages?

Question

Hi,

Lazarus Ide can use several gui libraries. I am on Windows. I wonder what are difference among them... It is clear that lcl is most stable.

Why would anyone use Qt and fpgui once they will be of good quality?

Answer 1

LCL is the abstraction. IOW the core part of the LCL works on all platforms. It's a bit Windows centric since it derives base principles (and compatibility) from Delphi's Windows centric VCL.

Under Windows, the LCL typically uses the win32/64 GDI API layer as backend, but it can also use others, most notably QT and GTK2 (though these are more in testing stages)

If you have majorly invested in making a complex GUI app under Linux, and have used QT specific functionality, the LCL-with-QT backend would e.g. allow you to more easily port this code over.

IOW using anything but win32/64 (GDI) on Windows is only in interesting specific purposes, with codebases that go beyond the LCL from non Windows origin.

FPGUI is a one man mission to create an own (owner drawn) widgetset. The LCL port was planned, but never delivered. Typically these kind of GUIs are used in embedded POS environment where the application essentially runs fullscreen. It probably also works on Windows since it's ownerdrawn and probably requires only a few basic primitives to get it working, and porting it to windows eases development.