E-book viewer: Add an option to allow only a single book to be viewed at a time. Trying to view a second book will cause it to replace the currently viewed book. Fixes #1526504 [view: reuse current instance option](https://bugs.launchpad.net/calibre/+bug/1526504)

src/calibre/gui2/viewer/config.py

@@ -291,8 +291,9 @@ class ConfigDialog(QDialog, Ui_Dialog):
     def restore_defaults(self):
         opts = config('').parse()
         self.load_options(opts)
-        from calibre.gui2.viewer.main import dprefs
+        from calibre.gui2.viewer.main import dprefs, vprefs
         self.word_lookups = dprefs.defaults['word_lookups']
+        self.opt_singleinstance.setChecked(vprefs.defaults['singleinstance'])
 
     def load_options(self, opts):
         self.opt_remember_window_size.setChecked(opts.remember_window_size)
@@ -344,6 +345,8 @@ class ConfigDialog(QDialog, Ui_Dialog):
             setattr(self, 'current_%s_color'%x, getattr(opts, '%s_color'%x))
         self.update_sample_colors()
         self.opt_show_controls.setChecked(opts.show_controls)
+        from calibre.gui2.viewer.main import vprefs
+        self.opt_singleinstance.setChecked(bool(vprefs['singleinstance']))
 
     def change_color(self, which, reset=False):
         if reset:
@@ -429,5 +432,6 @@ class ConfigDialog(QDialog, Ui_Dialog):
         c.set('show_controls', self.opt_show_controls.isChecked())
         for x in ('top', 'bottom', 'side'):
             c.set(x+'_margin', int(getattr(self, 'opt_%s_margin'%x).value()))
-        from calibre.gui2.viewer.main import dprefs
+        from calibre.gui2.viewer.main import dprefs, vprefs
         dprefs['word_lookups'] = self.word_lookups
+        vprefs['singleinstance'] = self.opt_singleinstance.isChecked()

src/calibre/gui2/viewer/config.ui

@@ -68,7 +68,7 @@ QToolBox::tab:hover {
             <x>0</x>
             <y>0</y>
             <width>799</width>
-            <height>378</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -241,7 +241,7 @@ QToolBox::tab:hover {
             <x>0</x>
             <y>0</y>
             <width>799</width>
-            <height>378</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -414,8 +414,8 @@ QToolBox::tab:hover {
            <rect>
             <x>0</x>
             <y>0</y>
-            <width>381</width>
+            <width>799</width>
-            <height>193</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -516,8 +516,8 @@ QToolBox::tab:hover {
            <rect>
             <x>0</x>
             <y>0</y>
-            <width>340</width>
+            <width>799</width>
-            <height>70</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -595,8 +595,8 @@ QToolBox::tab:hover {
            <rect>
             <x>0</x>
             <y>0</y>
-            <width>384</width>
+            <width>799</width>
-            <height>140</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -673,8 +673,8 @@ QToolBox::tab:hover {
            <rect>
             <x>0</x>
             <y>0</y>
-            <width>479</width>
+            <width>799</width>
-            <height>226</height>
+            <height>370</height>
            </rect>
           </property>
           <attribute name="label">
@@ -688,20 +688,36 @@ QToolBox::tab:hover {
              </property>
             </widget>
            </item>
-           <item row="5" column="0" colspan="2">
-            <widget class="QCheckBox" name="opt_remember_current_page">
-             <property name="text">
-              <string>Remember the &amp;current page when quitting</string>
-             </property>
-            </widget>
-           </item>
            <item row="6" column="0" colspan="2">
             <widget class="QCheckBox" name="opt_copy_bookmarks_to_file">
              <property name="toolTip">
               <string>Keep a copy of all bookmarks/current page information inside the ebook file, so that you can share them by simply sending the ebook file itself. Currently only works with ebooks in the EPUB format.</string>
              </property>
              <property name="text">
-              <string>Keep a copy of bookmarks/current page inside the ebook file, for easy sharing</string>
+              <string>Keep a copy of &amp;bookmarks/current page inside the ebook file, for easy sharing</string>
+             </property>
+            </widget>
+           </item>
+           <item row="3" column="1">
+            <widget class="QLineEdit" name="search_online_url">
+             <property name="toolTip">
+              <string>Change the search engine used to perform online searches for selected text.
+You must enter the search URL for the search engine, with the placeholder
+{text}, which will be replaced by the selected text.</string>
+             </property>
+            </widget>
+           </item>
+           <item row="1" column="1">
+            <widget class="QComboBox" name="hyphenate_default_lang">
+             <property name="toolTip">
+              <string>The default language to use for hyphenation rules. If the book does not specify a language, this will be used.</string>
+             </property>
+            </widget>
+           </item>
+           <item row="5" column="0" colspan="2">
+            <widget class="QCheckBox" name="opt_remember_current_page">
+             <property name="text">
+              <string>Remember the &amp;current page when quitting</string>
              </property>
             </widget>
            </item>
@@ -719,7 +735,7 @@ QToolBox::tab:hover {
              </property>
             </widget>
            </item>
-           <item row="7" column="0">
+           <item row="8" column="0">
             <widget class="QPushButton" name="clear_search_history_button">
              <property name="text">
               <string>Clear search history</string>
@@ -736,13 +752,6 @@ QToolBox::tab:hover {
              </property>
             </widget>
            </item>
-           <item row="1" column="1">
-            <widget class="QComboBox" name="hyphenate_default_lang">
-             <property name="toolTip">
-              <string>The default language to use for hyphenation rules. If the book does not specify a language, this will be used.</string>
-             </property>
-            </widget>
-           </item>
            <item row="3" column="0">
             <widget class="QLabel" name="label_26">
              <property name="text">
@@ -753,16 +762,7 @@ QToolBox::tab:hover {
              </property>
             </widget>
            </item>
-           <item row="3" column="1">
+           <item row="9" column="0">
-            <widget class="QLineEdit" name="search_online_url">
-             <property name="toolTip">
-              <string>Change the search engine used to perform online searches for selected text.
-You must enter the search URL for the search engine, with the placeholder
-{text}, which will be replaced by the selected text.</string>
-             </property>
-            </widget>
-           </item>
-           <item row="8" column="0">
             <spacer name="verticalSpacer">
              <property name="orientation">
               <enum>Qt::Vertical</enum>
@@ -775,6 +775,16 @@ You must enter the search URL for the search engine, with the placeholder
              </property>
             </spacer>
            </item>
+           <item row="7" column="0" colspan="2">
+            <widget class="QCheckBox" name="opt_singleinstance">
+             <property name="toolTip">
+              <string>Normally, you can view multiple books in calibre, each in its own viewer window. With this option, if you attempt to view a second book, it will replace the previously opened book instead of using a new window.</string>
+             </property>
+             <property name="text">
+              <string>Allow only a &amp;single book to be viewed at a time (needs restart)</string>
+             </property>
+            </widget>
+           </item>
           </layout>
          </widget>
         </widget>

src/calibre/gui2/viewer/main.py

@@ -8,7 +8,7 @@ from collections import namedtuple
 
 from PyQt5.Qt import (
     QApplication, Qt, QIcon, QTimer, QByteArray, QSize, QTime,
-    QPropertyAnimation, QUrl, QInputDialog, QAction, QModelIndex)
+    QPropertyAnimation, QUrl, QInputDialog, QAction, QModelIndex, pyqtSignal)
 
 from calibre.gui2.viewer.ui import Main as MainWindow
 from calibre.gui2.viewer.toc import TOC
@@ -20,14 +20,17 @@ from calibre.ebooks.oeb.iterator.book import EbookIterator
 from calibre.constants import islinux, filesystem_encoding
 from calibre.utils.config import Config, StringConfig, JSONConfig
 from calibre.customize.ui import available_input_formats
-from calibre import as_unicode, force_unicode, isbytestring
+from calibre import as_unicode, force_unicode, isbytestring, prints
 from calibre.ptempfile import reset_base_dir
+from calibre.utils.ipc import viewer_socket_address, RC
 from calibre.utils.zipfile import BadZipfile
 from calibre.utils.localization import canonicalize_lang, lang_as_iso639_1, get_lang
 
 vprefs = JSONConfig('viewer')
+vprefs.defaults['singleinstance'] = False
 dprefs = JSONConfig('viewer_dictionaries')
 dprefs.defaults['word_lookups'] = {}
+singleinstance_name = 'calibre_viewer'
 
 class Worker(Thread):
 
@@ -70,6 +73,19 @@ def lookup_website(lang):
     wm = dprefs['word_lookups']
     return wm.get(lang, default_lookup_website(lang))
 
+def listen(self):
+    while True:
+        try:
+            conn = self.listener.accept()
+        except Exception:
+            break
+        try:
+            self.msg_from_anotherinstance.emit(conn.recv())
+            conn.close()
+        except Exception as e:
+            prints('Failed to read message from other instance with error: %s' % as_unicode(e))
+    self.listener = None
+
 class EbookViewer(MainWindow):
 
     STATE_VERSION = 2
@@ -78,13 +94,20 @@ class EbookViewer(MainWindow):
     PAGED_MODE_TT = _('Switch to flow mode - where the text is not broken up '
             'into pages')
     AUTOSAVE_INTERVAL = 10  # seconds
+    msg_from_anotherinstance = pyqtSignal(object)
 
     def __init__(self, pathtoebook=None, debug_javascript=False, open_at=None,
-                 start_in_fullscreen=False, continue_reading=False):
+                 start_in_fullscreen=False, continue_reading=False, listener=None):
         MainWindow.__init__(self, debug_javascript)
         self.view.magnification_changed.connect(self.magnification_changed)
         self.closed = False
         self.show_toc_on_open = False
+        self.listener = listener
+        if listener is not None:
+            t = Thread(name='ConnListener', target=listen, args=(self,))
+            t.daemon = True
+            t.start()
+            self.msg_from_anotherinstance.connect(self.another_instance_wants_to_talk, type=Qt.QueuedConnection)
         self.current_book_has_toc = False
         self.iterator          = None
         self.current_page      = None
@@ -271,6 +294,8 @@ class EbookViewer(MainWindow):
             self.action_full_screen.trigger()
             return False
         self.save_state()
+        if self.listener is not None:
+            self.listener.close()
         return True
 
     def quit(self):
@@ -858,6 +883,14 @@ class EbookViewer(MainWindow):
             except:
                 traceback.print_exc()
 
+    def another_instance_wants_to_talk(self, msg):
+        try:
+            path, open_at = msg
+        except Exception:
+            return
+        self.load_ebook(path, open_at=open_at)
+        self.raise_()
+
     def load_ebook(self, pathtoebook, open_at=None, reopen_at=None):
         if self.iterator is not None:
             self.save_current_position()
@@ -1080,6 +1113,40 @@ View an ebook.
     setup_gui_option_parser(parser)
     return parser
 
+def create_listener():
+    if islinux:
+        from calibre.utils.ipc.server import LinuxListener as Listener
+    else:
+        from multiprocessing.connection import Listener
+    return Listener(address=viewer_socket_address())
+
+
+def ensure_single_instance(args, open_at):
+    try:
+        from calibre.utils.lock import singleinstance
+        si = singleinstance(singleinstance_name)
+    except Exception:
+        import traceback
+        error_dialog(None, _('Cannot start viewer'), _(
+            'Failed to start viewer, single instance locking failed. Click "Show Details" for more information'),
+                    det_msg=traceback.format_exc(), show=True)
+        raise SystemExit(1)
+    if not si:
+        if len(args) > 1:
+            t = RC(print_error=True, socket_address=viewer_socket_address())
+            t.start()
+            t.join(3.0)
+            if t.is_alive() or t.conn is None:
+                error_dialog(None, _('Connect talk to viewer'), _(
+                    'Unable to connect to existing viewer window, try restarting it.'), show=True)
+                raise SystemExit(1)
+            t.conn.send((os.path.abspath(args[1]), open_at))
+            t.conn.close()
+            prints('Opened book in existing viewer instance')
+        raise SystemExit(0)
+    listener = create_listener()
+    return listener
+
 
 def main(args=sys.argv):
     # Ensure viewer can continue to function if GUI is closed
@@ -1089,15 +1156,25 @@ def main(args=sys.argv):
     parser = option_parser()
     opts, args = parser.parse_args(args)
     open_at = float(opts.open_at.replace(',', '.')) if opts.open_at else None
+    listener = None
     override = 'calibre-ebook-viewer' if islinux else None
     app = Application(args, override_program_name=override, color_prefs=vprefs)
     app.load_builtin_fonts()
     app.setWindowIcon(QIcon(I('viewer.png')))
     QApplication.setOrganizationName(ORG_NAME)
     QApplication.setApplicationName(APP_UID)
+
+    if vprefs['singleinstance']:
+        try:
+            listener = ensure_single_instance(args, open_at)
+        except Exception as e:
+            import traceback
+            error_dialog(None, _('Failed to start viewer'), as_unicode(e), det_msg=traceback.format_exc(), show=True)
+            raise SystemExit(1)
+
     main = EbookViewer(args[1] if len(args) > 1 else None,
             debug_javascript=opts.debug_javascript, open_at=open_at, continue_reading=opts.continue_reading,
-                       start_in_fullscreen=opts.full_screen)
+                       start_in_fullscreen=opts.full_screen, listener=listener)
     app.installEventFilter(main)
     # This is needed for paged mode. Without it, the first document that is
     # loaded will have extra blank space at the bottom, as
@@ -1115,4 +1192,3 @@ def main(args=sys.argv):
 
 if __name__ == '__main__':
     sys.exit(main())
-

src/calibre/utils/ipc/__init__.py

@@ -11,7 +11,7 @@ from threading import Thread
 
 from calibre.constants import iswindows, get_windows_username, islinux
 
-ADDRESS = None
+ADDRESS = VADDRESS = None
 
 def eintr_retry_call(func, *args, **kwargs):
     while True:
@@ -48,10 +48,39 @@ def gui_socket_address():
                 ADDRESS = os.path.join(tmp, user+'-calibre-gui.socket')
     return ADDRESS
 
+
+def viewer_socket_address():
+    global VADDRESS
+    if VADDRESS is None:
+        if iswindows:
+            VADDRESS = r'\\.\pipe\CalibreViewer'
+            try:
+                user = get_windows_username()
+            except:
+                user = None
+            if user:
+                from calibre.utils.filenames import ascii_filename
+                user = ascii_filename(user).replace(' ', '_')
+                if user:
+                    VADDRESS += '-' + user[:100] + 'x'
+        else:
+            user = os.environ.get('USER', '')
+            if not user:
+                user = os.path.basename(os.path.expanduser('~'))
+            if islinux:
+                VADDRESS = (u'\0%s-calibre-viewer.socket' % user).encode('ascii')
+            else:
+                from tempfile import gettempdir
+                tmp = gettempdir()
+                VADDRESS = os.path.join(tmp, user+'-calibre-viewer.socket')
+    return VADDRESS
+
+
 class RC(Thread):
 
-    def __init__(self, print_error=True):
+    def __init__(self, print_error=True, socket_address=None):
         self.print_error = print_error
+        self.socket_address = socket_address or gui_socket_address()
         Thread.__init__(self)
         self.conn = None
         self.daemon = True
@@ -60,11 +89,9 @@ class RC(Thread):
         from multiprocessing.connection import Client
         self.done = False
         try:
-            self.conn = Client(gui_socket_address())
+            self.conn = Client(self.socket_address)
             self.done = True
         except:
             if self.print_error:
                 import traceback
                 traceback.print_exc()
-
-