Uw eigen plugins schrijven om de functionaliteit van calibre uit te breiden

calibre has a very modular design. Almost all functionality in calibre comes in the form of plugins. Plugins are used for conversion, for downloading news (though these are called recipes), for various components of the user interface, to connect to different devices, to process files when adding them to calibre and so on. You can get a complete list of all the built-in plugins in calibre by going to Preferences → Advanced → Plugins.

Hier laten we zien hoe u uw eigen plugins kunt maken om nieuwe functies toe te voegen aan calibre.

Notitie

Dit is enkel van toepassing op calibre releases >= 0.8.60

Opbouw van een calibre plugin

A calibre plugin is very simple, it’s just a ZIP file that contains some Python code and any other resources like image files needed by the plugin. Without further ado, let’s see a basic example.

Aangenomen u heeft calibre geïnstalleerd om diverse e-documenten zelf te publiceren in EPUB en MOBI-formaten. U wilt alle bestanden genereren in calibre en als uitgever als “Hello world”, hier volgt hoe u dit kunt doen. Maak een bestand aan genaamd __init__.py (dit is een speciale naa en moet altijd gebruikt worden voor het hoofdbestand van uw plugin) en geef de volgende Python code in:

import os
from calibre.customize import FileTypePlugin

class HelloWorld(FileTypePlugin):

    name                = 'Hello World Plugin' # Name of the plugin
    description         = 'Set the publisher to Hello World for all new conversions'
    supported_platforms = ['windows', 'osx', 'linux'] # Platforms this plugin will run on
    author              = 'Acme Inc.' # The author of this plugin
    version             = (1, 0, 0)   # The version number of this plugin
    file_types          = set(['epub', 'mobi']) # The file types that this plugin will be applied to
    on_postprocess      = True # Run this plugin after conversion is complete
    minimum_calibre_version = (0, 7, 53)

    def run(self, path_to_ebook):
        from calibre.ebooks.metadata.meta import get_metadata, set_metadata
        file = open(path_to_ebook, 'r+b')
        ext  = os.path.splitext(path_to_ebook)[-1][1:].lower()
        mi = get_metadata(file, ext)
        mi.publisher = 'Hello World'
        set_metadata(file, mi, ext)
        return path_to_ebook


Dat is alles. Om deze code toe te voegen aan calibre als een pluging, laat eenvoudig het volgende lopen in de map waarin u het bestand __init__.py heeft gemaakt:

calibre-customize -b .

Notitie

On macOS, the command line tools are inside the calibre bundle, for example, if you installed calibre in /Applications the command line tools are in /Applications/calibre.app/Contents/console.app/Contents/MacOS/.

U kunt de Hello World plugin downloaden van helloworld_plugin.zip.

Elke keer als u calibre gebruikt om een boek te converteren, wordt plugin run() methode opgeroepen en het geconverteerde boek heeft als uitgever “Hello World”. Dit is een onbenullig plugin. Laten we verdergaan naar een ingewikkelder voorbeeld dat daadwerkelijk een component toevoegt aan het gebruikersinterface.

Een gebruikersinterface plugin

This plugin will be spread over a few files (to keep the code clean). It will show you how to get resources (images or data files) from the plugin ZIP file, allow users to configure your plugin, how to create elements in the calibre user interface and how to access and query the books database in calibre.

U kunt dit plugin downloaden op interface_demo_plugin.zip

The first thing to note is that this ZIP file has a lot more files in it, explained below, pay particular attention to plugin-import-name-interface_demo.txt.

plugin-import-name-interface_demo.txt

An empty text file used to enable the multi-file plugin magic. This file must be present in all plugins that use more than one .py file. It should be empty and its filename must be of the form: plugin-import-name-**some_name**.txt. The presence of this file allows you to import code from the .py files present inside the ZIP file, using a statement like:

from calibre_plugins.some_name.some_module import some_object

The prefix calibre_plugins must always be present. some_name comes from the filename of the empty text file. some_module refers to some_module.py file inside the ZIP file. Note that this importing is just as powerful as regular Python imports. You can create packages and subpackages of .py modules inside the ZIP file, just like you would normally (by defining __init__.py in each sub-directory), and everything should “just work”.

The name you use for some_name enters a global namespace shared by all plugins, so make it as unique as possible. But remember that it must be a valid Python identifier (only alphabets, numbers and the underscore).

__init__.py
Zoals hiervoor, dit bestand definieërd de klasse van de plugin
main.py
Dit bestand bevat de daadwerkelijke code die iets nuttigs doet
ui.py
Dit bestand definieërd de interface van de plugin
images/icon.png
Het icoon voor deze plugin
about.txt
Een tekstbestand met informatie over uw plugin
vertalingen
Een map die .mo-bestanden bevat met de vertalingen van het gebruikersinterface van uw plugin in verschillende talen. Zie hieronder voor details.

Laten we naar de code kijken

__init__.py

Eerst de verplichte __init__.py om de metadata voor de plugin te definiëren:

# The class that all Interface Action plugin wrappers must inherit from
from calibre.customize import InterfaceActionBase

class InterfacePluginDemo(InterfaceActionBase):
    '''
    This class is a simple wrapper that provides information about the actual
    plugin class. The actual interface plugin class is called InterfacePlugin
    and is defined in the ui.py file, as specified in the actual_plugin field
    below.

    The reason for having two classes is that it allows the command line
    calibre utilities to run without needing to load the GUI libraries.
    '''
    name                = 'Interface Plugin Demo'
    description         = 'An advanced plugin demo'
    supported_platforms = ['windows', 'osx', 'linux']
    author              = 'Kovid Goyal'
    version             = (1, 0, 0)
    minimum_calibre_version = (0, 7, 53)

    #: This field defines the GUI plugin class that contains all the code
    #: that actually does something. Its format is module_path:class_name
    #: The specified class must be defined in the specified module.
    actual_plugin       = 'calibre_plugins.interface_demo.ui:InterfacePlugin'

    def is_customizable(self):
        '''
        This method must return True to enable customization via
        Preferences->Plugins
        '''
        return True

    def config_widget(self):
        '''
        Implement this method and :meth:`save_settings` in your plugin to
        use a custom configuration dialog.

        This method, if implemented, must return a QWidget. The widget can have
        an optional method validate() that takes no arguments and is called
        immediately after the user clicks OK. Changes are applied if and only
        if the method returns True.

        If for some reason you cannot perform the configuration at this time,
        return a tuple of two strings (message, details), these will be
        displayed as a warning dialog to the user and the process will be
        aborted.

        The base class implementation of this method raises NotImplementedError
        so by default no user configuration is possible.
        '''
        # It is important to put this import statement here rather than at the
        # top of the module as importing the config class will also cause the
        # GUI libraries to be loaded, which we do not want when using calibre
        # from the command line
        from calibre_plugins.interface_demo.config import ConfigWidget
        return ConfigWidget()

    def save_settings(self, config_widget):
        '''
        Save the settings specified by the user with config_widget.

        :param config_widget: The widget returned by :meth:`config_widget`.
        '''
        config_widget.save_settings()

        # Apply the changes
        ac = self.actual_plugin_
        if ac is not None:
            ac.apply_settings()


The only noteworthy feature is the field actual_plugin. Since calibre has both command line and GUI interfaces, GUI plugins like this one should not load any GUI libraries in __init__.py. The actual_plugin field does this for you, by telling calibre that the actual plugin is to be found in another file inside your ZIP archive, which will only be loaded in a GUI context.

Remember that for this to work, you must have a plugin-import-name-some_name.txt file in your plugin ZIP file, as discussed above.

Er zijn meerdere methoden om gebruikers-configuratie van de plugin mogelijk te maken. Deze worden hieronder besproken.

ui.py

Laten we nu ul.py bekijken dat de eigenlijke GUI plugin definiëert. De broncode is voorzien van commentaar en zou zichzelf moeten verklaren:

# The class that all interface action plugins must inherit from
from calibre.gui2.actions import InterfaceAction
from calibre_plugins.interface_demo.main import DemoDialog

class InterfacePlugin(InterfaceAction):

    name = 'Interface Plugin Demo'

    # Declare the main action associated with this plugin
    # The keyboard shortcut can be None if you dont want to use a keyboard
    # shortcut. Remember that currently calibre has no central management for
    # keyboard shortcuts, so try to use an unusual/unused shortcut.
    action_spec = ('Interface Plugin Demo', None,
            'Run the Interface Plugin Demo', 'Ctrl+Shift+F1')

    def genesis(self):
        # This method is called once per plugin, do initial setup here

        # Set the icon for this interface action
        # The get_icons function is a builtin function defined for all your
        # plugin code. It loads icons from the plugin zip file. It returns
        # QIcon objects, if you want the actual data, use the analogous
        # get_resources builtin function.
        #
        # Note that if you are loading more than one icon, for performance, you
        # should pass a list of names to get_icons. In this case, get_icons
        # will return a dictionary mapping names to QIcons. Names that
        # are not found in the zip file will result in null QIcons.
        icon = get_icons('images/icon.png')

        # The qaction is automatically created from the action_spec defined
        # above
        self.qaction.setIcon(icon)
        self.qaction.triggered.connect(self.show_dialog)

    def show_dialog(self):
        # The base plugin object defined in __init__.py
        base_plugin_object = self.interface_action_base_plugin
        # Show the config dialog
        # The config dialog can also be shown from within
        # Preferences->Plugins, which is why the do_user_config
        # method is defined on the base plugin class
        do_user_config = base_plugin_object.do_user_config

        # self.gui is the main calibre GUI. It acts as the gateway to access
        # all the elements of the calibre user interface, it should also be the
        # parent of the dialog
        d = DemoDialog(self.gui, self.qaction.icon(), do_user_config)
        d.show()

    def apply_settings(self):
        from calibre_plugins.interface_demo.config import prefs
        # In an actual non trivial plugin, you would probably need to
        # do something based on the settings in prefs
        prefs

main.py

De eigenlijke opzet om het Interface Plugin Demo dialoogvenster te implementeren.

from PyQt5.Qt import QDialog, QVBoxLayout, QPushButton, QMessageBox, QLabel

from calibre_plugins.interface_demo.config import prefs

class DemoDialog(QDialog):

    def __init__(self, gui, icon, do_user_config):
        QDialog.__init__(self, gui)
        self.gui = gui
        self.do_user_config = do_user_config

        # The current database shown in the GUI
        # db is an instance of the class LibraryDatabase from db/legacy.py
        # This class has many, many methods that allow you to do a lot of
        # things. For most purposes you should use db.new_api, which has
        # a much nicer interface from db/cache.py
        self.db = gui.current_db

        self.l = QVBoxLayout()
        self.setLayout(self.l)

        self.label = QLabel(prefs['hello_world_msg'])
        self.l.addWidget(self.label)

        self.setWindowTitle('Interface Plugin Demo')
        self.setWindowIcon(icon)

        self.about_button = QPushButton('About', self)
        self.about_button.clicked.connect(self.about)
        self.l.addWidget(self.about_button)

        self.marked_button = QPushButton(
            'Show books with only one format in the calibre GUI', self)
        self.marked_button.clicked.connect(self.marked)
        self.l.addWidget(self.marked_button)

        self.view_button = QPushButton(
            'View the most recently added book', self)
        self.view_button.clicked.connect(self.view)
        self.l.addWidget(self.view_button)

        self.update_metadata_button = QPushButton(
            'Update metadata in a book\'s files', self)
        self.update_metadata_button.clicked.connect(self.update_metadata)
        self.l.addWidget(self.update_metadata_button)

        self.conf_button = QPushButton(
                'Configure this plugin', self)
        self.conf_button.clicked.connect(self.config)
        self.l.addWidget(self.conf_button)

        self.resize(self.sizeHint())

    def about(self):
        # Get the about text from a file inside the plugin zip file
        # The get_resources function is a builtin function defined for all your
        # plugin code. It loads files from the plugin zip file. It returns
        # the bytes from the specified file.
        #
        # Note that if you are loading more than one file, for performance, you
        # should pass a list of names to get_resources. In this case,
        # get_resources will return a dictionary mapping names to bytes. Names that
        # are not found in the zip file will not be in the returned dictionary.
        text = get_resources('about.txt')
        QMessageBox.about(self, 'About the Interface Plugin Demo',
                text.decode('utf-8'))

    def marked(self):
        ''' Show books with only one format '''
        db = self.db.new_api
        matched_ids = {book_id for book_id in db.all_book_ids() if len(db.formats(book_id)) == 1}
        # Mark the records with the matching ids
        # new_api does not know anything about marked books, so we use the full
        # db object
        self.db.set_marked_ids(matched_ids)

        # Tell the GUI to search for all marked records
        self.gui.search.setEditText('marked:true')
        self.gui.search.do_search()

    def view(self):
        ''' View the most recently added book '''
        most_recent = most_recent_id = None
        db = self.db.new_api
        for book_id, timestamp in db.all_field_for('timestamp', db.all_book_ids()).iteritems():
            if most_recent is None or timestamp > most_recent:
                most_recent = timestamp
                most_recent_id = book_id

        if most_recent_id is not None:
            # Get a reference to the View plugin
            view_plugin = self.gui.iactions['View']
            # Ask the view plugin to launch the viewer for row_number
            view_plugin._view_calibre_books([most_recent_id])

    def update_metadata(self):
        '''
        Set the metadata in the files in the selected book's record to
        match the current metadata in the database.
        '''
        from calibre.ebooks.metadata.meta import set_metadata
        from calibre.gui2 import error_dialog, info_dialog

        # Get currently selected books
        rows = self.gui.library_view.selectionModel().selectedRows()
        if not rows or len(rows) == 0:
            return error_dialog(self.gui, 'Cannot update metadata',
                             'No books selected', show=True)
        # Map the rows to book ids
        ids = list(map(self.gui.library_view.model().id, rows))
        db = self.db.new_api
        for book_id in ids:
            # Get the current metadata for this book from the db
            mi = db.get_metadata(book_id, get_cover=True, cover_as_data=True)
            fmts = db.formats(book_id)
            if not fmts:
                continue
            for fmt in fmts:
                fmt = fmt.lower()
                # Get a python file object for the format. This will be either
                # an in memory file or a temporary on disk file
                ffile = db.format(book_id, fmt, as_file=True)
                ffile.seek(0)
                # Set metadata in the format
                set_metadata(ffile, mi, fmt)
                ffile.seek(0)
                # Now replace the file in the calibre library with the updated
                # file. We dont use add_format_with_hooks as the hooks were
                # already run when the file was first added to calibre.
                db.add_format(book_id, fmt, ffile, run_hooks=False)

        info_dialog(self, 'Updated files',
                'Updated the metadata in the files of %d book(s)'%len(ids),
                show=True)

    def config(self):
        self.do_user_config(parent=self)
        # Apply the changes
        self.label.setText(prefs['hello_world_msg'])

Getting resources from the plugin ZIP file

calibre’s plugin loading system defines a couple of built-in functions that allow you to conveniently get files from the plugin ZIP file.

get_resources(name_or_list_of_names)
This function should be called with a list of paths to files inside the ZIP file. For example to access the file icon.png in the directory images in the ZIP file, you would use: images/icon.png. Always use a forward slash as the path separator, even on windows. When you pass in a single name, the function will return the raw bytes of that file or None if the name was not found in the ZIP file. If you pass in more than one name then it returns a dict mapping the names to bytes. If a name is not found, it will not be present in the returned dict.
get_icons(name_or_list_of_names)
A convenience wrapper for get_resources() that creates QIcon objects from the raw bytes returned by get_resources. If a name is not found in the ZIP file the corresponding QIcon will be null.

Gebruikers-configuratie van uw plugin toevoegen

To allow users to configure your plugin, you must define three methods in your base plugin class, is_customizable, config_widget and save_settings as shown below:

    def is_customizable(self):
        '''
        This method must return True to enable customization via
        Preferences->Plugins
        '''
        return True
    def config_widget(self):
        '''
        Implement this method and :meth:`save_settings` in your plugin to
        use a custom configuration dialog.

        This method, if implemented, must return a QWidget. The widget can have
        an optional method validate() that takes no arguments and is called
        immediately after the user clicks OK. Changes are applied if and only
        if the method returns True.

        If for some reason you cannot perform the configuration at this time,
        return a tuple of two strings (message, details), these will be
        displayed as a warning dialog to the user and the process will be
        aborted.

        The base class implementation of this method raises NotImplementedError
        so by default no user configuration is possible.
        '''
        # It is important to put this import statement here rather than at the
        # top of the module as importing the config class will also cause the
        # GUI libraries to be loaded, which we do not want when using calibre
        # from the command line
        from calibre_plugins.interface_demo.config import ConfigWidget
        return ConfigWidget()
    def save_settings(self, config_widget):
        '''
        Save the settings specified by the user with config_widget.

        :param config_widget: The widget returned by :meth:`config_widget`.
        '''
        config_widget.save_settings()

        # Apply the changes
        ac = self.actual_plugin_
        if ac is not None:
            ac.apply_settings()

calibre heeft vele manieren om configuratie-gegevens te bewaren (een erfenis van vroeger). De aanbevolen manier is het gebruik van de JSONConfig class, welke de informatie bewaard in een .json-bestand.

De code om configuratie-gegevens te beheren in de demo-plugin is in config.py:

from PyQt5.Qt import QWidget, QHBoxLayout, QLabel, QLineEdit

from calibre.utils.config import JSONConfig

# This is where all preferences for this plugin will be stored
# Remember that this name (i.e. plugins/interface_demo) is also
# in a global namespace, so make it as unique as possible.
# You should always prefix your config file name with plugins/,
# so as to ensure you dont accidentally clobber a calibre config file
prefs = JSONConfig('plugins/interface_demo')

# Set defaults
prefs.defaults['hello_world_msg'] = 'Hello, World!'

class ConfigWidget(QWidget):

    def __init__(self):
        QWidget.__init__(self)
        self.l = QHBoxLayout()
        self.setLayout(self.l)

        self.label = QLabel('Hello world &message:')
        self.l.addWidget(self.label)

        self.msg = QLineEdit(self)
        self.msg.setText(prefs['hello_world_msg'])
        self.l.addWidget(self.msg)
        self.label.setBuddy(self.msg)

    def save_settings(self):
        prefs['hello_world_msg'] = unicode(self.msg.text())

Het prefs-object is nu beschikbaar in de plugincode met een simpele:

from calibre_plugins.interface_demo.config import prefs

U kunt het gebruik van prefs-object zien in main.py:

    def config(self):
        self.do_user_config(parent=self)
        # Apply the changes
        self.label.setText(prefs['hello_world_msg'])

Edit book plugins

Laten we in een hogere versnelling schakelen en het maken van een plugin bekijken dat gereedschappen toevoegt aan calibre’s boek-editor. De plugin is hier beschikbaar: editor_demo_plugin.zip.

De eerste stap zoals voor alle plugins is het maken van het lege import name txt-bestand zoals boven beschreven. We noemen het bestand plugin-import-name-editor_plugin_demo.txt.

Nu maken we het verplichte bestand __init__.py waarin de metadata over de plugin staan – zijn naam, maker, versie enz.


from calibre.customize import EditBookToolPlugin


class DemoPlugin(EditBookToolPlugin):

    name = 'Edit Book plugin demo'
    version = (1, 0, 0)
    author = 'Kovid Goyal'
    supported_platforms = ['windows', 'osx', 'linux']
    description = 'A demonstration of the plugin interface for the ebook editor'
    minimum_calibre_version = (1, 46, 0)

Een enkel editor-plugin kan meerdere gereedschappen leveren, ieder gereedschap correspondeert met een enkele knop in de werkbalk en trefwoord in het Plugins-menu in de editor. Deze kunnen sub-menu’s hebben indien het gereedschap meerdere acties heeft.

De gereedschappen moeten allemaal gedefiniëerd zijn in het bestand main.py in uw plugin. Ieder gereedschap in een class, dat erft van de calibre.gui2.tweak_book.plugin.Tool class. Laten we een kijkje nemen in main.py van de demo-plugin, de broncode is voorzien van commentaar en zou zichzelf moeten verklaren. Lees de API-documenten van de calibre.gui2.tweak_book.plugin.Tool class voor meer details.

main.py

Hier zien we de definitie van een enkel gereedschap dat alle lettergroottes in het boek multipliceert met een getal ingesteld door de gebruiker. Dit gereedschap demonstreert meerdere belangrijke concepten die u nodig heeft omuw eigen plugin te ontwikkelen. Lees daarom de (van commentaar voorziene) broncode grondig.


import re
from PyQt5.Qt import QAction, QInputDialog
from cssutils.css import CSSRule

# The base class that all tools must inherit from
from calibre.gui2.tweak_book.plugin import Tool

from calibre import force_unicode
from calibre.gui2 import error_dialog
from calibre.ebooks.oeb.polish.container import OEB_DOCS, OEB_STYLES, serialize

class DemoTool(Tool):

    #: Set this to a unique name it will be used as a key
    name = 'demo-tool'

    #: If True the user can choose to place this tool in the plugins toolbar
    allowed_in_toolbar = True

    #: If True the user can choose to place this tool in the plugins menu
    allowed_in_menu = True

    def create_action(self, for_toolbar=True):
        # Create an action, this will be added to the plugins toolbar and
        # the plugins menu
        ac = QAction(get_icons('images/icon.png'), 'Magnify fonts', self.gui)  # noqa
        if not for_toolbar:
            # Register a keyboard shortcut for this toolbar action. We only
            # register it for the action created for the menu, not the toolbar,
            # to avoid a double trigger
            self.register_shortcut(ac, 'magnify-fonts-tool', default_keys=('Ctrl+Shift+Alt+D',))
        ac.triggered.connect(self.ask_user)
        return ac

    def ask_user(self):
        # Ask the user for a factor by which to multiply all font sizes
        factor, ok = QInputDialog.getDouble(
            self.gui, 'Enter a magnification factor', 'Allow font sizes in the book will be multiplied by the specified factor',
            value=2, min=0.1, max=4
        )
        if ok:
            # Ensure any in progress editing the user is doing is present in the container
            self.boss.commit_all_editors_to_container()
            try:
                self.magnify_fonts(factor)
            except Exception:
                # Something bad happened report the error to the user
                import traceback
                error_dialog(self.gui, _('Failed to magnify fonts'), _(
                    'Failed to magnify fonts, click "Show details" for more info'),
                    det_msg=traceback.format_exc(), show=True)
                # Revert to the saved restore point
                self.boss.revert_requested(self.boss.global_undo.previous_container)
            else:
                # Show the user what changes we have made, allowing her to
                # revert them if necessary
                self.boss.show_current_diff()
                # Update the editor UI to take into account all the changes we
                # have made
                self.boss.apply_container_update_to_gui()

    def magnify_fonts(self, factor):
        # Magnify all font sizes defined in the book by the specified factor
        # First we create a restore point so that the user can undo all changes
        # we make.
        self.boss.add_savepoint('Before: Magnify fonts')

        container = self.current_container  # The book being edited as a container object

        # Iterate over all style declarations in the book, this means css
        # stylesheets, <style> tags and style="" attributes
        for name, media_type in container.mime_map.iteritems():
            if media_type in OEB_STYLES:
                # A stylesheet. Parsed stylesheets are cssutils CSSStylesheet
                # objects.
                self.magnify_stylesheet(container.parsed(name), factor)
                container.dirty(name)  # Tell the container that we have changed the stylesheet
            elif media_type in OEB_DOCS:
                # A HTML file. Parsed HTML files are lxml elements

                for style_tag in container.parsed(name).xpath('//*[local-name="style"]'):
                    if style_tag.text and style_tag.get('type', None) in {None, 'text/css'}:
                        # We have an inline CSS <style> tag, parse it into a
                        # stylesheet object
                        sheet = container.parse_css(style_tag.text)
                        self.magnify_stylesheet(sheet, factor)
                        style_tag.text = serialize(sheet, 'text/css', pretty_print=True)
                        container.dirty(name)  # Tell the container that we have changed the stylesheet
                for elem in container.parsed(name).xpath('//*[@style]'):
                    # Process inline style attributes
                    block = container.parse_css(elem.get('style'), is_declaration=True)
                    self.magnify_declaration(block, factor)
                    elem.set('style', force_unicode(block.getCssText(separator=' '), 'utf-8'))

    def magnify_stylesheet(self, sheet, factor):
        # Magnify all fonts in the specified stylesheet by the specified
        # factor.
        for rule in sheet.cssRules.rulesOfType(CSSRule.STYLE_RULE):
            self.magnify_declaration(rule.style, factor)

    def magnify_declaration(self, style, factor):
        # Magnify all fonts in the specified style declaration by the specified
        # factor
        val = style.getPropertyValue('font-size')
        if not val:
            return
        # see if the font-size contains a number
        num = re.search(r'[0-9.]+', val)
        if num is not None:
            num = num.group()
            val = val.replace(num, '%f' % (float(num) * factor))
            style.setProperty('font-size', val)
        # We should also be dealing with the font shorthand property and
        # font sizes specified as non numbers, but those are left as exercises
        # for the reader

Laten we main.py in onderdelen bekijken. We zien dat een enkel gereedschap wordt gefeniniëerd genoemd Magnify fonts - letters vergroten. Dit gereedschap vraagt aan de gebruiker om een getal in te geven en vermenigvuldigt alle lettergroottes in het boek met dit getal.

Het eerste belangrijke ding is de naam van het gereedschap die u moet bepalen op een relatief unieke tekenreeks omdat deze wordt gebruikt als toets voor dit gereedschap.

The next important entry point is the calibre.gui2.tweak_book.plugin.Tool.create_action(). This method creates the QAction objects that appear in the plugins toolbar and plugin menu. It also, optionally, assigns a keyboard shortcut that the user can customize. The triggered signal from the QAction is connected to the ask_user() method that asks the user for the font size multiplier, and then runs the magnification code.

The magnification code is well commented and fairly simple. The main things to note are that you get a reference to the editor window as self.gui and the editor Boss as self.boss. The Boss is the object that controls the editor user interface. It has many useful methods, that are documented in the calibre.gui2.tweak_book.boss.Boss class.

Finally, there is self.current_container which is a reference to the book being edited as a calibre.ebooks.oeb.polish.container.Container object. This represents the book as a collection of its constituent HTML/CSS/image files and has convenience methods for doing many useful things. The container object and various useful utility functions that can be reused in your plugin code are documented in API documentation for the e-book editing tools.

Vertalingen toevoegen aan uw plugin

U kunt de teksten in het gebruikersinterface in uw plugin laten vertalen in elke taal die is ingesteld voor het calibre gebruikersinterface.

De eerste stap in de broncodes in uw plugin te doorzoeken naar voor gebruikers zichtbare teksten te doorzoeken en deze te markeren als vertaalbaar door ze te omgeven met _(). Bijvoorbeeld:

action_spec = (_('My plugin'), None, _('My plugin is cool'), None)

Then use some program to generate .po files from your plugin source code. There should be one .po file for every language you want to translate into. For example: de.po for German, fr.po for French and so on. You can use the poedit program for this.

Verstuur deze .po-bestanden naar uw vertalers. Nadat ze vertaald zijn, compileer ze in .mo-bestanden. Wederom kunt u poedit hiervoor gebruiken of eenvoudig het volgende doen:

calibre-debug -c "from calibre.translations.msgfmt import main; main()" filename.po

Plaats de .mo-bestanden in de vertalingen-map in uw plugin.

De laatste stap is om eenvoudig de functie load_translations() op te roepen bovenin uw .py-bestanden in uw plugin. Om de prestatie niet te vertragen moet u deze functie alleen aanroepen in die .py-bestanden die daadwerkelijk vertaalbare teksten bevatten. Dus in een normaal Gebruikersinterface plugin roept u deze functie wel aan bovenin ui.py maar niet in __init__.py.

You can test the translations of your plugins by changing the user interface language in calibre under Preferences → Interface → Look & feel or by running calibre like this:

CALIBRE_OVERRIDE_LANG=de calibre

Vervang de met de taalcode van de taal die u wilt testen.

De plugin API

Zoals u misschien heeft opgemerkt is een plugin in calibre een class. Er zijn verschillende classes voor verschillende types plugin. Details van iedere class, inclusief de basis class van alle plugins zijn te vinden in API documentation for plugins.

Uw plugin zal bijna zeker code gebruiken van calibre. Om te leren hoe u diverse stukjes functionaliteit vindt in de calibre code basis, lees de sectie Code opmaak.

Plugins debuggen

De eerste en belangrijkste stap is het laten werken van calibre in foutenopsporingsmodus. U kunt dit doen in de opdrachtregel met:

calibre-debug -g

Or from within calibre by right-clicking the Preferences button or using the Ctrl+Shift+R keyboard shortcut.

Wanneer u werkt met de opdrachtregel verschijnt de debugging op de console, wanneer u werkt in calbre zal dit worden geschreven naar een .txt-bestand.

You can insert print statements anywhere in your plugin code, they will be output in debug mode. Remember, this is Python, you really shouldn’t need anything more than print statements to debug ;) I developed all of calibre using just this debugging technique.

U kunt snel wijzigingen aan uw plugin testen met behulp van de volgende opdrachtregel:

calibre-debug -s; calibre-customize -b /path/to/your/plugin/directory; calibre

Dit sluit een lopende calibre af, wacht totdat het programma geheel afgesloten is, dan uw plugin updaten in calibre en calibre herstarten.

Meer voorbeelden van plugins

Je kan een lijst vinden van vele, gesoftikeerde plugins hier terug vinden: here.

Uw plugins delen met anderen

Als je wenst de plugins te delen die je gemaakt hebt, met andere gebruiks van calibre, maak een nieuw onderwerp aan in calibre plugins forum.