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#### 17.5.7.9 Hooks

Hooks are variables which contain Lisp functions (or lists of functions) which are called at various times. Calc defines a number of hooks that help you to customize it in various ways. Calc uses the Lisp function `run-hooks` to invoke the hooks shown below. Several other customization-related variables are also described here.

Variable: calc-load-hook

  This hook is called at the end of `calc.el`, after the file has been loaded, before any functions in it have been called, but after `calc-mode-map` and similar variables have been set up.

Variable: calc-ext-load-hook

  This hook is called at the end of `calc-ext.el`.

Variable: calc-start-hook

  This hook is called as the last step in a `M-x calc` command. At this point, the Calc buffer has been created and initialized if necessary, the Calc window and trail window have been created, and the “Welcome to Calc” message has been displayed.

Variable: calc-mode-hook

  This hook is called when the Calc buffer is being created. Usually this will only happen once per Emacs session. The hook is called after Emacs has switched to the new buffer, the mode-settings file has been read if necessary, and all other buffer-local variables have been set up. After this hook returns, Calc will perform a `calc-refresh` operation, set up the mode line display, then evaluate any deferred `calc-define` properties that have not been evaluated yet.

Variable: calc-trail-mode-hook

  This hook is called when the Calc Trail buffer is being created. It is called as the very last step of setting up the Trail buffer. Like `calc-mode-hook`, this will normally happen only once per Emacs session.

Variable: calc-end-hook

  This hook is called by `calc-quit`, generally because the user presses `q` or `C-x * c` while in Calc. The Calc buffer will be the current buffer. The hook is called as the very first step, before the Calc window is destroyed.

Variable: calc-window-hook

  If this hook is non-`nil`, it is called to create the Calc window. Upon return, this new Calc window should be the current window. (The Calc buffer will already be the current buffer when the hook is called.) If the hook is not defined, Calc will generally use `split-window`, `set-window-buffer`, and `select-window` to create the Calc window.

Variable: calc-trail-window-hook

  If this hook is non-`nil`, it is called to create the Calc Trail window. The variable `calc-trail-buffer` will contain the buffer which the window should use. Unlike `calc-window-hook`, this hook must not switch into the new window.

Variable: calc-embedded-mode-hook

  This hook is called the first time that Embedded mode is entered.

Variable: calc-embedded-new-buffer-hook

  This hook is called each time that Embedded mode is entered in a new buffer.

Variable: calc-embedded-new-formula-hook

  This hook is called each time that Embedded mode is enabled for a new formula.

Variable: calc-edit-mode-hook

  This hook is called by `calc-edit` (and the other “edit” commands) when the temporary editing buffer is being created. The buffer will have been selected and set up to be in `calc-edit-mode`, but will not yet have been filled with text. (In fact it may still have leftover text from a previous `calc-edit` command.)

Variable: calc-mode-save-hook

  This hook is called by the `calc-save-modes` command, after Calc’s own mode features have been inserted into the Calc init file and just before the “End of mode settings” message is inserted.

Variable: calc-reset-hook

  This hook is called after `C-x * 0` (`calc-reset`) has reset all modes. The Calc buffer will be the current buffer.

Variable: calc-other-modes

  This variable contains a list of strings. The strings are concatenated at the end of the modes portion of the Calc mode line (after standard modes such as “Deg”, “Inv” and “Hyp”). Each string should be a short, single word followed by a space. The variable is `nil` by default.

Variable: calc-mode-map

  This is the keymap that is used by Calc mode. The best time to adjust it is probably in a `calc-mode-hook`. If the Calc extensions package (`calc-ext.el`) has not yet been loaded, many of these keys will be bound to `calc-missing-key`, which is a command that loads the extensions package and “retypes” the key. If your `calc-mode-hook` rebinds one of these keys, it will probably be overridden when the extensions are loaded.

Variable: calc-digit-map

  This is the keymap that is used during numeric entry. Numeric entry uses the minibuffer, but this map binds every non-numeric key to `calcDigit-nondigit` which generally calls `exit-minibuffer` and “retypes” the key.

Variable: calc-alg-ent-map

  This is the keymap that is used during algebraic entry. This is mostly a copy of `minibuffer-local-map`.

Variable: calc-store-var-map

  This is the keymap that is used during entry of variable names for commands like `calc-store` and `calc-recall`. This is mostly a copy of `minibuffer-local-completion-map`.

Variable: calc-edit-mode-map

  This is the (sparse) keymap used by `calc-edit` and other temporary editing commands. It binds `RET`, `LFD`, and `C-c C-c` to `calc-edit-finish`.

Variable: calc-mode-var-list

  This is a list of variables which are saved by `calc-save-modes`. Each entry is a list of two items, the variable (as a Lisp symbol) and its default value. When modes are being saved, each variable is compared with its default value (using `equal`) and any non-default variables are written out.

Variable: calc-local-var-list

  This is a list of variables which should be buffer-local to the Calc buffer. Each entry is a variable name (as a Lisp symbol). These variables also have their default values manipulated by the `calc` and `calc-quit` commands; see Multiple Calculators. Since `calc-mode-hook` is called after this list has been used the first time, your hook should add a variable to the list and also call `make-local-variable` itself.

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