Use the Liberation fonts as the default fonts for generic css font specs on linux as the other fonts may result in bitmapped fonts being used

src/calibre/ebooks/conversion/plugins/pdf_output.py

@@ -10,7 +10,7 @@ Convert OEB ebook format to PDF.
 
 import glob, os
 
-from calibre.constants import iswindows
+from calibre.constants import iswindows, islinux
 from calibre.customize.conversion import (OutputFormatPlugin,
     OptionRecommendation)
 from calibre.ptempfile import TemporaryDirectory
@@ -73,13 +73,13 @@ class PDFOutput(OutputFormatPlugin):
                 ' of stretching it to fill the full first page of the'
                 ' generated pdf.')),
         OptionRecommendation(name='pdf_serif_family',
-            recommended_value='Times New Roman', help=_(
+            recommended_value='Liberation Serif' if islinux else 'Times New Roman', help=_(
                 'The font family used to render serif fonts')),
         OptionRecommendation(name='pdf_sans_family',
-            recommended_value='Helvetica', help=_(
+            recommended_value='Liberation Sans' if islinux else 'Helvetica', help=_(
                 'The font family used to render sans-serif fonts')),
         OptionRecommendation(name='pdf_mono_family',
-            recommended_value='Courier New', help=_(
+            recommended_value='Liberation Mono' if islinux else 'Courier New', help=_(
                 'The font family used to render monospaced fonts')),
         OptionRecommendation(name='pdf_standard_font', choices=['serif',
             'sans', 'mono'],
@@ -102,6 +102,10 @@ class PDFOutput(OutputFormatPlugin):
         ])
 
     def convert(self, oeb_book, output_path, input_plugin, opts, log):
+        from calibre.gui2 import must_use_qt, load_builtin_fonts
+        must_use_qt()
+        load_builtin_fonts()
+
         self.oeb = oeb_book
         self.input_plugin, self.opts, self.log = input_plugin, opts, log
         self.output_path = output_path
@@ -135,7 +139,6 @@ class PDFOutput(OutputFormatPlugin):
         If you ever move to Qt WebKit 2.3+ then this will be unnecessary.
         '''
         from calibre.ebooks.oeb.base import urlnormalize
-        from calibre.gui2 import must_use_qt
         from calibre.utils.fonts.utils import remove_embed_restriction
         from PyQt4.Qt import QFontDatabase, QByteArray, QRawFont, QFont
 
@@ -165,7 +168,6 @@ class PDFOutput(OutputFormatPlugin):
                         raw = remove_embed_restriction(raw)
                     except:
                         continue
-                    must_use_qt()
                     fid = QFontDatabase.addApplicationFontFromData(QByteArray(raw))
                     family_name = None
                     if fid > -1:

src/calibre/gui2/__init__.py

@@ -766,6 +766,26 @@ class Translator(QTranslator):
 gui_thread = None
 
 qt_app = None
+
+def load_builtin_fonts():
+    global _rating_font
+    # Load the builtin fonts and any fonts added to calibre by the user to
+    # Qt
+    for ff in glob.glob(P('fonts/liberation/*.?tf')) + \
+            [P('fonts/calibreSymbols.otf')] + \
+            glob.glob(os.path.join(config_dir, 'fonts', '*.?tf')):
+        if ff.rpartition('.')[-1].lower() in {'ttf', 'otf'}:
+            with open(ff, 'rb') as s:
+                # Windows requires font files to be executable for them to be
+                # loaded successfully, so we use the in memory loader
+                fid = QFontDatabase.addApplicationFontFromData(s.read())
+                if fid > -1:
+                    fam = QFontDatabase.applicationFontFamilies(fid)
+                    fam = set(map(unicode, fam))
+                    if u'calibre Symbols' in fam:
+                        _rating_font = u'calibre Symbols'
+
+
 class Application(QApplication):
 
     def __init__(self, args, force_calibre_style=False,
@@ -798,27 +818,12 @@ class Application(QApplication):
                 return ret
 
     def load_builtin_fonts(self, scan_for_fonts=False):
-        global _rating_font
         if scan_for_fonts:
             from calibre.utils.fonts.scanner import font_scanner
             # Start scanning the users computer for fonts
             font_scanner
 
-        # Load the builtin fonts and any fonts added to calibre by the user to
-        # Qt
-        for ff in glob.glob(P('fonts/liberation/*.?tf')) + \
-                [P('fonts/calibreSymbols.otf')] + \
-                glob.glob(os.path.join(config_dir, 'fonts', '*.?tf')):
-            if ff.rpartition('.')[-1].lower() in {'ttf', 'otf'}:
-                with open(ff, 'rb') as s:
-                    # Windows requires font files to be executable for them to be
-                    # loaded successfully, so we use the in memory loader
-                    fid = QFontDatabase.addApplicationFontFromData(s.read())
-                    if fid > -1:
-                        fam = QFontDatabase.applicationFontFamilies(fid)
-                        fam = set(map(unicode, fam))
-                        if u'calibre Symbols' in fam:
-                            _rating_font = u'calibre Symbols'
+        load_builtin_fonts()
 
     def load_calibre_style(self):
         # On OS X QtCurve resets the palette, so we preserve it explicitly