bug#52142: 28.0.60; `posn-object-width-height' does not reflect actual dimensions of object when confronted by display string

[Po Lu]

In Emacs -Q, run M-x report-emacs-bug RET, move point to the message
intended for novices (This bug report will be sent to the Bug-GNU-Emacs
mailing list ...), and then evaluate (posn-at-point) there.

The posn-object of the position list will be the display string
containing the entire message, but the posn-object-width-height will
contain the dimensions of the first character of the message, in this
case "T".

Thanks.