Created attachment 148004 [details]
Initial auth dialog, fully on screen

SUMMARY

The VPN secrets dialog initially appears with a small size, but then enlarges itself to include all the widgets required for authentication.  If the dialog is initially positioned along the bottom of the screen, the enlarged dialog will have some of its content moved offscreen.  The Login button can become partially or completely hidden.

STEPS TO REPRODUCE
0. Configure a VPN that requires authentication.  I'm using a GlobalProtect VPN via OpenConnect.
1. Arrange windows such that the window manager will place the VPN dialog along the bottom of the screen.
2. Right-click the plasma-nm applet in the system tray and connect to the VPN.

OBSERVED RESULT
The VPN secrets dialog will appear with a "Contacting host, please wait..." message.  Once the authentication process starts, the dialog gets bigger to include the username + password fields, but since the dialog was already at the bottom of the screen, the larger size pushes some of the window past the bottom so it's not completely visible.

The not-fully-visible parts include the Login button, which makes the missing content very noticeable.

EXPECTED RESULT
The entire dialog should be on screen - especially the Login button.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: Arch Linux current as of this writing, Wayland session
(available in About System)
KDE Plasma Version: 5.24.4
KDE Frameworks Version: 5.92.0
Qt Version: 5.15.3

ADDITIONAL INFORMATION
Height of the dialog in kded/passworddialog.ui is currently set to 147.  If I enlarge that to 480, that's enough height to make this issue go away for me.  But I'm not sure if that would be acceptable for other use cases for this dialog.  I'm not sure if there's any upper limit on how big the dialog could need to be.

Alternatively, if it's KWin's job to move the window when it gets bigger, then this bug is invalid and I can file one against KWin instead.

I'm attaching screenshots of the initial and truncated windows.  These screenshots are of the bottom-right corner of my desktop, with some windows in the background to encourage KWin to place the VPN dialog at the bottom.