Fix for slowdown if a file URL refers to a missing drive. Might be a windows-only thing.

src/calibre/gui2/comments_editor.py

@@ -28,7 +28,7 @@ from calibre.gui2.widgets import LineEditECM
 from calibre.gui2.widgets2 import to_plain_text
 from calibre.utils.config import tweaks
 from calibre.utils.imghdr import what
-from polyglot.builtins import filter, iteritems, itervalues, unicode_type
+from polyglot.builtins import filter, iteritems, itervalues, unicode_type, as_bytes
 
 # Cleanup Qt markup {{{
 
@@ -764,7 +764,7 @@ class EditorWidget(QTextEdit, LineEditECM):  # {{{
                     with lopen(path, 'rb') as f:
                         data = f.read()
                 except EnvironmentError:
-                    pass
+                    return QByteArray(I('blank-1x1.png', data=True))
                 else:
                     return QByteArray(data)
 

src/calibre/gui2/widgets2.py

@@ -11,7 +11,7 @@ from PyQt5.Qt import (
     QDialogButtonBox, QFont, QFontInfo, QFontMetrics, QIcon, QKeySequence, QLabel,
     QLayout, QPalette, QPixmap, QPoint, QPushButton, QRect, QScrollArea, QSize,
     QSizePolicy, QStyle, QStyledItemDelegate, Qt, QTabWidget, QTextBrowser,
-    QToolButton, QUndoCommand, QUndoStack, QWidget, pyqtSignal
+    QToolButton, QUndoCommand, QUndoStack, QWidget, pyqtSignal, QByteArray
 )
 
 from calibre.ebooks.metadata import rating_to_stars
@@ -482,6 +482,18 @@ class HTMLDisplay(QTextBrowser):
                 return
         self.anchor_clicked.emit(qurl)
 
+    def loadResource(self, rtype, qurl):
+        if qurl.isLocalFile():
+            path = qurl.toLocalFile()
+            try:
+                with lopen(path, 'rb') as f:
+                    data = f.read()
+            except EnvironmentError:
+                return QByteArray(I('blank-1x1.png', data=True))
+            else:
+                return QByteArray(data)
+        else:
+            QTextBrowser.loadResource(self, rtype, qurl)
 
 class ScrollingTabWidget(QTabWidget):