QtLCL have full support for MDI on all supported platforms (linux,mac & win).If you need TDI , then under QtLCL it could be setted up via QMdiArea_setViewMode() ...
https://svn.code.sf.net/p/lazarus-ccr/svn/components/tdi/
What I do, usually, for tabbed interfaces is implement the "inner" tabs as frames That way you keep most of the easiness of UI implementation that forms provide.
Quote from: PeterX on July 13, 2016, 05:01:29 pmhttps://github.com/fpc-svn/lazarus-ccr/tree/master/components/tdiYour link seems to be broken.Did you mean?https://github.com/svn2github/lazarus-ccr/tree/master/components/tdi
https://github.com/fpc-svn/lazarus-ccr/tree/master/components/tdi