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107 lines
4.4 KiB
Plaintext
107 lines
4.4 KiB
Plaintext
Writing an IDLE extension
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An IDLE extension can define new key bindings and menu entries for IDLE
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edit windows. There is a simple mechanism to load extensions when IDLE
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starts up and to attach them to each edit window. (It is also possible
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to make other changes to IDLE, but this must be done by editing the IDLE
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source code.)
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The list of extensions loaded at startup time is configured by editing
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the file extend.py; see below for details.
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An IDLE extension is defined by a class. Methods of the class define
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actions that are invoked by those bindings or menu entries. Class (or
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instance) variables define the bindings and menu additions; these are
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automatically applied by IDLE when the extension is linked to an edit
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window.
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An IDLE extension class is instantiated with a single argument,
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`editwin', an EditorWindow instance. The extension cannot assume much
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about this argument, but it is guarateed to have the following instance
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variables:
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text a Text instance (a widget)
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io an IOBinding instance (more about this later)
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flist the FileList instance (shared by all edit windows)
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(There are a few more, but they are rarely useful.)
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The extension class must not bind key events. Rather, it must define
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one or more virtual events, e.g. <<zoom-height>>, and corresponding
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methods, e.g. zoom_height_event(), and have one or more class (or instance)
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variables that define mappings between virtual events and key sequences,
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e.g. <Alt-F2>. When the extension is loaded, these key sequences will
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be bound to the corresponding virtual events, and the virtual events
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will be bound to the corresponding methods. (This indirection is done
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so that the key bindings can easily be changed, and so that other
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sources of virtual events can exist, such as menu entries.)
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The following class or instance variables are used to define key
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bindings for virtual events:
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keydefs for all platforms
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mac_keydefs for Macintosh
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windows_keydefs for Windows
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unix_keydefs for Unix (and other platforms)
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Each of these variables, if it exists, must be a dictionary whose
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keys are virtual events, and whose values are lists of key sequences.
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An extension can define menu entries in a similar fashion. This is done
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with a class or instance variable named menudefs; it should be a list of
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pair, where each pair is a menu name (lowercase) and a list of menu
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entries. Each menu entry is either None (to insert a separator entry) or
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a pair of strings (menu_label, virtual_event). Here, menu_label is the
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label of the menu entry, and virtual_event is the virtual event to be
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generated when the entry is selected. An underscore in the menu label
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is removed; the character following the underscore is displayed
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underlined, to indicate the shortcut character (for Windows).
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At the moment, extensions cannot define whole new menus; they must
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define entries in existing menus. Some menus are not present on some
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windows; such entry definitions are then ignored, but the key bindings
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are still applied. (This should probably be refined in the future.)
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Here is a complete example example:
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class ZoomHeight:
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menudefs = [
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('edit', [
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None, # Separator
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('_Zoom Height', '<<zoom-height>>'),
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])
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]
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windows_keydefs = {
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'<<zoom-height>>': ['<Alt-F2>'],
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}
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unix_keydefs = {
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'<<zoom-height>>': ['<Control-z><Control-z>'],
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}
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def __init__(self, editwin):
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self.editwin = editwin
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def zoom_height_event(self, event):
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"...Do what you want here..."
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The final piece of the puzzle is the file "extend.py", which contains a
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simple table used to configure the loading of extensions. This file
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currently contains a single list variable named "standard", which is a
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list of extension names that are to be loaded. (In the future, other
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configuration variables may be added to this module.)
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Extensions can define key bindings and menu entries that reference
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events they don't implement (including standard events); however this is
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not recommended (and may be forbidden in the future).
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Extensions are not required to define menu entries for all events they
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implement.
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Note: in order to change key bindings, you must currently edit the file
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keydefs. It contains two dictionaries named and formatted like the
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keydefs dictionaries described above, one for the Unix bindings and one
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for the Windows bindings. In the future, a better mechanism will be
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provided.
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