Subject: bug#12377: 24.2.50; `minibuffer-prompt-properties' should respect existing faces in prompt string

From: Drew Adams <[email-masked]>
Date: Thu, 28 Apr 2016 17:21:36 -0700 (PDT)

Dunno why this needs to be done in C code anyway.

It is OK for Emacs to make the prompt read-only, I guess (i.e., to not let user code make it writable), though I would prefer that it just do that by default.

It is OK for Emacs to apply face `minibuffer-prompt' or whatever, by default.

It is not OK for Emacs to overwrite any text properties.

In general, user code should be allowed to do anything it wants to the prompt text. But Emacs should provide, by default, a read-only prompt with its standard face.

And it should be done in Lisp, preferably, so users can easily modify it at will.  This is Emacs.  There is nothing critical for performance about setting up the minibuffer prompt string.