Function: frame-visible-p
frame-visible-p is a function defined in frame.c.
Signature
(frame-visible-p FRAME)
Documentation
Return t if FRAME is "visible" (actually in use for display).
Return the symbol icon if FRAME is iconified or "minimized".
Return nil if FRAME was made invisible, via make-frame-invisible.
On graphical displays, invisible frames are not updated and are
usually not displayed at all, even in a window system's "taskbar".
If FRAME is a text terminal frame, this always returns t. Such frames are always considered visible, whether or not they are currently being displayed on the terminal.
Source Code
// Defined in /usr/src/emacs/src/frame.c
{
CHECK_LIVE_FRAME (frame);
if (FRAME_VISIBLE_P (XFRAME (frame)))
return Qt;
if (FRAME_ICONIFIED_P (XFRAME (frame)))
return Qicon;
return Qnil;
}