Add fromaework for viewer plugins

src/calibre/customize/__init__.py

@@ -654,3 +654,36 @@ class StoreBase(Plugin): # {{{
         raise NotImplementedError()
 
 # }}}
+
+class ViewerPlugin(Plugin): # {{{
+
+    '''
+    These plugins are used to add functionality to the calibre viewer.
+    '''
+
+    def load_fonts(self):
+        '''
+        This method is called once at viewer starup. It should load any fonts
+        it wants to make available. For example::
+
+            def load_fonts():
+                from PyQt4.Qt import QFontDatabase
+                font_data = get_resources(['myfont1.ttf', 'myfont2.ttf'])
+                for raw in font_data.itervalues():
+                    QFontDatabase.addApplicationFontFromData(raw)
+        '''
+        pass
+
+    def load_javascript(self, evaljs):
+        '''
+        This method is called every time a new HTML document is loaded in the
+        viewer. Use it to load javascript libraries into the viewer. For
+        example::
+
+            def load_javascript(self, evaljs):
+                js = get_resources('myjavascript.js')
+                evaljs(js)
+        '''
+        pass
+# }}}
+

src/calibre/customize/ui.py

@@ -8,7 +8,7 @@ from calibre.customize import (CatalogPlugin, FileTypePlugin, PluginNotFound,
                               MetadataReaderPlugin, MetadataWriterPlugin,
                               InterfaceActionBase as InterfaceAction,
                               PreferencesPlugin, platform, InvalidPlugin,
-                              StoreBase as Store)
+                              StoreBase as Store, ViewerPlugin)
 from calibre.customize.conversion import InputFormatPlugin, OutputFormatPlugin
 from calibre.customize.zipplugin import loader
 from calibre.customize.profiles import InputProfile, OutputProfile
@@ -481,6 +481,13 @@ def all_metadata_plugins():
             yield plugin
 # }}}
 
+# Viewer plugins {{{
+def all_viewer_plugins():
+    for plugin in _initialized_plugins:
+        if isinstance(plugin, ViewerPlugin):
+            yield plugin
+# }}}
+
 # Initialize plugins {{{
 
 _initialized_plugins = []

src/calibre/gui2/viewer/documentview.py

@@ -17,6 +17,7 @@ from PyQt4.QtWebKit import QWebPage, QWebView, QWebSettings
 from calibre.gui2.viewer.flip import SlideFlip
 from calibre.gui2.shortcuts import Shortcuts
 from calibre import prints
+from calibre.customize.ui import all_viewer_plugins
 from calibre.gui2.viewer.keys import SHORTCUTS
 from calibre.gui2.viewer.javascript import JavaScriptLoader
 from calibre.gui2.viewer.position import PagePosition
@@ -90,6 +91,8 @@ class Document(QWebPage): # {{{
 
         # Fonts
         load_builtin_fonts()
+        for pl in all_viewer_plugins():
+            pl.load_fonts()
         self.set_font_settings()
 
         # Security
@@ -169,8 +172,11 @@ class Document(QWebPage): # {{{
         if self.loaded_javascript:
             return
         self.loaded_javascript = True
-        self.loaded_lang = self.js_loader(self.mainFrame().evaluateJavaScript,
-                self.current_language, self.hyphenate_default_lang)
+        evaljs = self.mainFrame().evaluateJavaScript
+        self.loaded_lang = self.js_loader(evaljs, self.current_language,
+                self.hyphenate_default_lang)
+        for pl in all_viewer_plugins():
+            pl.load_javascript(evaljs)
 
     @pyqtSignature("")
     def animated_scroll_done(self):