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6.3 Hooks

Hemlock actions such as setting variables, changing buffers, changing windows, turning modes on and off, etc., often have hooks associated with them. A hook is a list of functions called before the system performs the action. The manual describes the object specific hooks with the rest of the operations defined on these objects.

Often hooks are stored in Hemlock variables, Delete Buffer Hook and Set Window Hook for example. This leads to a minor point of confusion because these variables have hooks that the system executes when someone changes their values. These hook functions Hemlock invokes when someone sets a variable are an example of a hook stored in an object instead of a Hemlock variable. These are all hooks for editor activity, but Hemlock keeps them in different kinds of locations. This is why some of the routines in this section have a special interpretation of the hook place argument.

Macro: Macro add-hook place hook-fun ¶

Macro: Macro remove-hook place hook-fun ¶

These macros add or remove a hook function in some place. If hook-fun already exists in place, this call has no effect. If place is a symbol, then it is a Hemlock variable; otherwise, it is a generalized variable or storage location. Here are two examples:

(add-hook delete-buffer-hook 'remove-buffer-from-menu)

(add-hook (variable-hooks 'check-mail-interval)
          'reschedule-mail-check)

Macro: invoke-hook place &rest args ¶

This macro calls all the functions in place. If place is a symbol, then it is a Hemlock variable; otherwise, it is a generalized variable.