Kindle driver: Add an option to allow using page counts stored in a custom column. Go to Preferences->Plugins and customize the Kindle driver, to tell it to use a custom column to get page count data.

src/calibre/devices/kindle/apnx.py

@@ -19,7 +19,12 @@ class APNXBuilder(object):
     Create an APNX file using a pseudo page mapping.
     '''
 
-    def write_apnx(self, mobi_file_path, apnx_path, accurate=True):
+    def write_apnx(self, mobi_file_path, apnx_path, accurate=True, page_count=0):
+        '''
+        If you want a fixed number of pages (such as from a custom column) then
+        pass in a value to page_count, otherwise a count will be estimated
+        using either the fast or accurate algorithm.
+        '''
         # Check that this is really a MOBI file.
         with open(mobi_file_path, 'rb') as mf:
             ident = PdbHeaderReader(mf).identity()
@@ -28,6 +33,9 @@ class APNXBuilder(object):
 
         # Get the pages depending on the chosen parser
         pages = []
+        if page_count:
+            pages = self.get_pages_exact(mobi_file_path, page_count)
+        else:
             if accurate:
                 try:
                     pages = self.get_pages_accurate(mobi_file_path)
@@ -77,6 +85,31 @@ class APNXBuilder(object):
 
         return apnx
 
+    def get_pages_exact(self, mobi_file_path, page_count):
+        '''
+        Given a specified page count (such as from a custom column),
+        create our array of pages for the apnx file by dividing by
+        the content size of the book.
+        '''
+        pages = []
+        count = 0
+
+        with open(mobi_file_path, 'rb') as mf:
+            phead = PdbHeaderReader(mf)
+            r0 = phead.section_data(0)
+            text_length = struct.unpack('>I', r0[4:8])[0]
+
+        chars_per_page = int(text_length / page_count)
+        while count < text_length:
+            pages.append(count)
+            count += chars_per_page
+
+        if len(pages) > page_count:
+            # Rounding created extra page entries
+            pages = pages[:page_count]
+
+        return pages
+
     def get_pages_fast(self, mobi_file_path):
         '''
         2300 characters of uncompressed text per page. This is

src/calibre/devices/kindle/driver.py

@@ -302,19 +302,28 @@ class KINDLE2(KINDLE):
               ' this information to the Kindle when uploading MOBI files by'
               ' USB. Note that the page numbers do not correspond to any paper'
               ' book.'),
-        _('Use slower but more accurate page number generation') +
+        _('Use slower but more accurate page number calculation') +
             ':::' +
             _('There are two ways to generate the page number information. Using the more accurate '
               'generator will produce pages that correspond better to a printed book. '
               'However, this method is slower and will slow down sending files '
               'to the Kindle.'),
+        _('Custom column name to retrieve page counts from') +
+            ':::' +
+            _('If you have a custom column in your library that you use to '
+              'store the page count of books, you can have calibre use that '
+              'information, instead of calculating a page count. Specify the '
+              'name of the custom column here, for example, #pages. '),
+
     ]
     EXTRA_CUSTOMIZATION_DEFAULT = [
         True,
         False,
+        '',
     ]
     OPT_APNX           = 0
     OPT_APNX_ACCURATE  = 1
+    OPT_APNX_CUST_COL  = 2
 
     def books(self, oncard=None, end_session=True):
         bl = USBMS.books(self, oncard=oncard, end_session=end_session)
@@ -380,10 +389,20 @@ class KINDLE2(KINDLE):
             if not os.path.exists(path):
                 os.makedirs(path)
 
+        cust_col_name = opts.extra_customization[self.OPT_APNX_CUST_COL]
+        custom_page_count = 0
+        if cust_col_name:
+            try:
+                custom_page_count = int(metadata.get(cust_col_name, 0))
+            except:
+                pass
+
         apnx_path = '%s.apnx' % os.path.join(path, filename)
         apnx_builder = APNXBuilder()
         try:
-            apnx_builder.write_apnx(filepath, apnx_path, accurate=opts.extra_customization[self.OPT_APNX_ACCURATE])
+            apnx_builder.write_apnx(filepath, apnx_path,
+                                    accurate=opts.extra_customization[self.OPT_APNX_ACCURATE],
+                                    page_count=custom_page_count)
         except:
             print 'Failed to generate APNX'
             import traceback

src/calibre/gui2/device_drivers/configwidget.py

@@ -82,6 +82,7 @@ class ConfigWidget(QWidget, Ui_ConfigWidget):
                         self.opt_extra_customization.append(QLineEdit(self))
                         l = QLabel(label_text)
                         l.setToolTip(tt)
+                        self.opt_extra_customization[i].setToolTip(tt)
                         l.setBuddy(self.opt_extra_customization[i])
                         l.setWordWrap(True)
                         self.opt_extra_customization[i].setText(settings.extra_customization[i])