Every frame has a name parameter; this serves as the default
for the frame title which window systems typically display at the top of
the frame. You can specify a name explicitly by setting the name
frame property.
Normally you don’t specify the name explicitly, and Emacs computes the
frame name automatically based on a template stored in the variable
frame-title-format. Emacs recomputes the name each time the
frame is redisplayed.
This variable specifies how to compute a name for a frame when you
have not explicitly specified one (via the frame’s parameters;
see Basic Parameters). The variable’s value is actually a mode
line construct, just like mode-line-format, except that the
‘%c’, ‘%C’, and ‘%l’ constructs are ignored.
See The Data Structure of the Mode Line.
This variable specifies how to compute the name for an iconified frame
when you have not explicitly specified the frame’s name via the
frame’s parameters. The resulting title appears in the frame’s icon
itself. If the value is a string, is should be a mode line construct
like that of frame-title-format. The value can also be
t, which means to use frame-title-format instead; this
avoids problems with some window managers and desktop environments,
where a change in a frame’s title (when a frame is iconified) is
interpreted as a request to raise the frame and/or give it input
focus. It is also useful if you want the frame’s title to be the same
no matter if the frame is iconified or not. The default value is a
string identical to the default value of frame-title-format.
This variable is set automatically by Emacs. Its value is t when
there are two or more frames (not counting minibuffer-only frames or
invisible frames). The default value of frame-title-format uses
multiple-frames so as to put the buffer name in the frame title
only when there is more than one frame.
The value of this variable is not guaranteed to be accurate except
while processing frame-title-format or
icon-title-format.