When using inherited forms, when the master form has a FNCPageControl, with designtime predefined pages, it generates new PageControlConteiners in inherited forms, causing compiler and/or IDE show several errors, and sometimes making IDE raise runtime errors and crashes.
Ex.:
This is the parent form structure, with a pagecontrol, two pages and some other controls inside os those pages.
When I create a new form via File / New / Other / Inheritable Items / formMain , I get a inherited form with both pgPage1 & pgPage2 I defined on parent structure, and it creates a new control container for each page, that causes several errors:
I try to fix the DFM manually, but it's useless. Most times throws errors like:
In 2020 I had the same issue with some VCL Adv controls that had the same structure of sub-members (like in the Pages collection where items are TMSFNCPageControlsPage) defined apart of the corresponding Control Containers (like TTMSFNCPageControlContainer), but in that case, editting the inherited forms DFMs worked as a fix for some of them.
With FNCPageControl , when there are design-time pages, I can't use form inheritance neither in VCL nor in Web Core. Couldn't find a fix yet - only if I create pages and it's child controls at runtime.
Every time the DFM is generated or accessed, it seems to force that those auto-named pagecontainers are present.