Are file open dialogs part of the os or the app?

Help
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1

Coming from the WIndows stock fileopen dialog interface

(CoCreateInstance(CLSID_FileOpenDialog, NULL, CLSCTX_ALL, IID_IFileOpenDialog, reinterpret_cast<void**>(&pFileOpen))

wonder if something similar exists in plasma. Or is this a OS (Fedora) thing?

Use case: store KeepassXc key file on an Android sp connected using mtp:

2

The KDE plasma apps use the Qt tool kit.
Look at Qt’s open file dialog which I think is this QFileDialog Class | Qt Widgets | Qt 6.11.2
KDE framework may have it’s own version, but I’m sure about that.

3

Both, really. Some apps use baked-in file dialogs, or rather use a toolkit-specific one (Gtk, Qt, KDE, etc)

But a lot of things support Portals that allow an application to use the desktop’s native file chooser.

4

So. It’s a mess. is that my right assement of the UX situation?

5

Depends. With my Qt code the Qt defaults to use the OS dialog styles.
But developers can override that.