At any time, one frame in Emacs is the selected frame. The selected window always resides on the selected frame.
When Emacs displays its frames on several terminals (see Multiple Terminals), each terminal has its own selected frame. But only one of these is the selected frame: it’s the frame that belongs to the terminal from which the most recent input came. That is, when Emacs runs a command that came from a certain terminal, the selected frame is the one of that terminal. Since Emacs runs only a single command at any given time, it needs to consider only one selected frame at a time; this frame is what we call the selected frame in this manual. The display on which the selected frame is shown is the selected frame’s display.
This function returns the selected frame.
Some window systems and window managers direct keyboard input to the window object that the mouse is in; others require explicit clicks or commands to shift the focus to various window objects. Either way, Emacs automatically keeps track of which frames have focus. To explicitly switch to a different frame from a Lisp function, call select-frame-set-input-focus.
The plural “frames” in the previous paragraph is deliberate: while Emacs itself has only one selected frame, Emacs can have frames on many different terminals (recall that a connection to a window system counts as a terminal), and each terminal has its own idea of which frame has input focus. When you set the input focus to a frame, you set the focus for that frame’s terminal, but frames on other terminals may still remain focused.
Lisp programs can switch frames temporarily by calling the function select-frame. This does not alter the window system’s concept of focus; rather, it escapes from the window manager’s control until that control is somehow reasserted.
When using a text terminal, only one frame can be displayed at a time on the terminal, so after a call to select-frame, the next redisplay actually displays the newly selected frame. This frame remains selected until a subsequent call to select-frame. Each frame on a text terminal has a number which appears in the mode line before the buffer name (see Mode Line Variables).
This function selects frame, raises it (should it happen to be obscured by other frames) and tries to give it the window system’s focus. On a text terminal, the next redisplay displays the new frame on the entire terminal screen. The optional argument norecord has the same meaning as for select-frame (see below). The return value of this function is not significant.
Ideally, the function described next should focus a frame without also raising it above other frames. Unfortunately, many window-systems or window managers may refuse to comply.
This function gives frame the focus of the X server without necessarily raising it. frame nil means use the selected frame. Under X, the optional argument noactivate, if non-nil, means to avoid making frame’s window-system window the “active” window which should insist a bit more on avoiding to raise frame above other frames.
On MS-Windows the noactivate argument has no effect. However, if frame is a child frame (see Child Frames), this function usually focuses frame without raising it above other child frames.
If there is no window system support, this function does nothing.
This function selects frame frame, temporarily disregarding the focus of the X server if any. The selection of frame lasts until the next time the user does something to select a different frame, or until the next time this function is called. (If you are using a window system, the previously selected frame may be restored as the selected frame after return to the command loop, because it still may have the window system’s input focus.)
The specified frame becomes the selected frame, and its terminal becomes the selected terminal. This function then calls select-window as a subroutine, passing the window selected within frame as its first argument and norecord as its second argument (hence, if norecord is non-nil, this avoids changing the order of recently selected windows and the buffer list). See Selecting Windows.
This function returns frame, or nil if frame has been deleted.
In general, you should never use select-frame in a way that could switch to a different terminal without switching back when you’re done.
Emacs cooperates with the window system by arranging to select frames as the server and window manager request. When a window system informs Emacs that one of its frames has been selected, Emacs internally generates a focus-in event. When an Emacs frame is displayed on a text-terminal emulator, such as xterm, which supports reporting of focus-change notification, the focus-in and focus-out events are available even for text-mode frames. Focus events are normally handled by handle-focus-in.
This function handles focus-in events from window systems and terminals that support explicit focus notifications. It updates the per-frame focus flags that frame-focus-state queries and calls after-focus-change-function. In addition, it generates a switch-frame event in order to switch the Emacs notion of the selected frame to the frame most recently focused in some terminal. It’s important to note that this switching of the Emacs selected frame to the most recently focused frame does not mean that other frames do not continue to have the focus in their respective terminals. Do not invoke this function yourself: instead, attach logic to after-focus-change-function.
This function handles a switch-frame event, which Emacs generates for itself upon focus notification or under various other circumstances involving an input event arriving at a different frame from the last event. Do not invoke this function yourself.
This function redirects focus from frame to focus-frame. This means that focus-frame will receive subsequent keystrokes and events intended for frame. After such an event, the value of last-event-frame will be focus-frame. Also, switch-frame events specifying frame will instead select focus-frame.
If focus-frame is omitted or nil, that cancels any existing redirection for frame, which therefore once again receives its own events.
One use of focus redirection is for frames that don’t have minibuffers. These frames use minibuffers on other frames. Activating a minibuffer on another frame redirects focus to that frame. This puts the focus on the minibuffer’s frame, where it belongs, even though the mouse remains in the frame that activated the minibuffer.
Selecting a frame can also change focus redirections. Selecting frame bar, when foo had been selected, changes any redirections pointing to foo so that they point to bar instead. This allows focus redirection to work properly when the user switches from one frame to another using select-window.
This means that a frame whose focus is redirected to itself is treated differently from a frame whose focus is not redirected. select-frame affects the former but not the latter.
The redirection lasts until redirect-frame-focus is called to change it.
This function retrieves the last known focus state of frame.
It returns nil if the frame is known not to be focused, t if the frame is known to be focused, or unknown if Emacs does not know the focus state of the frame. (You may see this last state in TTY frames running on terminals that do not support explicit focus notifications.)
This function is an extension point that code can use to receive a notification that focus has changed.
This function is called with no arguments when Emacs notices that the set of focused frames may have changed. Code wanting to do something when frame focus changes should use add-function to add a function to this one, and in this added function, re-scan the set of focused frames, calling frame-focus-state to retrieve the last known focus state of each frame. Focus events are delivered asynchronously, and frame input focus according to an external system may not correspond to the notion of the Emacs selected frame. Multiple frames may appear to have input focus simultaneously due to focus event delivery differences, the presence of multiple Emacs terminals, and other factors, and code should be robust in the face of this situation.
Depending on window system, focus events may also be delivered repeatedly and with different focus states before settling to the expected values. Code relying on focus notifications should “debounce” any user-visible updates arising from focus changes, perhaps by deferring work until redisplay.
This function may be called in arbitrary contexts, including from inside read-event, so take the same care as you might when writing a process filter.
This option informs Emacs whether and how the window manager transfers focus when you move the mouse pointer into a frame. It can have three meaningful values:
nilThe default value nil should be used when your window manager follows a “click-to-focus” policy where you have to click the mouse inside of a frame in order for that frame to gain focus.
tThe value t should be used when your window manager has the focus automatically follow the position of the mouse pointer but a frame that gains focus is not raised automatically and may even remain occluded by other window-system windows.
auto-raiseThe value auto-raise should be used when your window manager has the focus automatically follow the position of the mouse pointer and a frame that gains focus is raised automatically.
If this option is non-nil, Emacs moves the mouse pointer to the frame selected by select-frame-set-input-focus. That function is used by a number of commands like, for example, other-frame and pop-to-buffer.
The distinction between the values t and auto-raise is not needed for “normal” frames because the window manager usually takes care of raising them. It is useful to automatically raise child frames via mouse-autoselect-window (see Mouse Window Auto-selection).
Note that this option does not distinguish “sloppy” focus (where the frame that previously had focus retains focus as long as the mouse pointer does not move into another window manager window) from “strict” focus (where a frame immediately loses focus when it’s left by the mouse pointer). Neither does it recognize whether your window manager supports delayed focusing or auto-raising where you can explicitly specify the time until a new frame gets focus or is auto-raised.
You can supply a “focus follows mouse” policy for individual Emacs windows by customizing the variable mouse-autoselect-window (see Mouse Window Auto-selection).
Copyright © 1990-1996, 1998-2019 Free Software Foundation, Inc.
Licensed under the GNU GPL license.
https://www.gnu.org/software/emacs/manual/html_node/elisp/Input-Focus.html