When running in debug mode, handle C++ exceptions raised in Qt slots, printing out some information about the exception

src/calibre/gui2/__init__.py

@@ -13,7 +13,7 @@ from PyQt4.Qt import (QVariant, QFileInfo, QObject, SIGNAL, QBuffer, Qt,
 ORG_NAME = 'KovidsBrain'
 APP_UID  = 'libprs500'
 from calibre.constants import (islinux, iswindows, isbsd, isfrozen, isosx,
-        config_dir, filesystem_encoding)
+        plugins, config_dir, filesystem_encoding, DEBUG)
 from calibre.utils.config import Config, ConfigProxy, dynamic, JSONConfig
 from calibre.ebooks.metadata import MetaInformation
 from calibre.utils.date import UNDEFINED_DATE
@@ -764,6 +764,7 @@ class Application(QApplication):
         if override_program_name:
             args = [override_program_name] + args[1:]
         qargs = [i.encode('utf-8') if isinstance(i, unicode) else i for i in args]
+        self.pi = plugins['progress_indicator'][0]
         QApplication.__init__(self, qargs)
         global gui_thread, qt_app
         gui_thread = QThread.currentThread()
@@ -773,16 +774,26 @@ class Application(QApplication):
         self._file_open_paths = []
         self._file_open_lock = RLock()
         self.setup_styles(force_calibre_style)
+        if DEBUG:
+            self.redirect_notify = True
+
+    if DEBUG:
+        def notify(self, receiver, event):
+            if self.redirect_notify:
+                self.redirect_notify = False
+                return self.pi.do_notify(receiver, event)
+            else:
+                ret = QApplication.notify(self, receiver, event)
+                self.redirect_notify = True
+                return ret
 
     def load_calibre_style(self):
         # On OS X QtCurve resets the palette, so we preserve it explicitly
         orig_pal = QPalette(self.palette())
 
-        from calibre.constants import plugins
-        pi = plugins['progress_indicator'][0]
         path = os.path.join(sys.extensions_location, 'calibre_style.'+(
             'pyd' if iswindows else 'so'))
-        pi.load_style(path, 'Calibre')
+        self.pi.load_style(path, 'Calibre')
         # On OSX, on some machines, colors can be invalid. See https://bugs.launchpad.net/bugs/1014900
         for role in (orig_pal.Button, orig_pal.Window):
             c = orig_pal.brush(role).color()

src/calibre/gui2/progress_indicator/QProgressIndicator.cpp

@@ -5,6 +5,7 @@
 #include <QPluginLoader>
 #include <QStyle>
 #include <QApplication>
+#include <QDebug>
 
 QProgressIndicator::QProgressIndicator(QWidget* parent, int size)
         : QWidget(parent),
@@ -145,3 +146,16 @@ int load_style(QString &path, QString &name) {
     }
     return ret;
 }
+
+bool do_notify(QObject *receiver, QEvent *event) {
+    try {
+        return QApplication::instance()->notify(receiver, event);
+    } catch (std::exception& e) {
+        qCritical() << "C++ exception thrown in slot: " << e.what();
+    } catch (...) {
+        qCritical() << "Unknown C++ exception thrown in slot";
+    }
+    qCritical() << "Receiver name:" << receiver->objectName() << "Receiver class:" << receiver->metaObject()->className() << "Event type: " << event->type();
+    return false;
+}
+

src/calibre/gui2/progress_indicator/QProgressIndicator.h

@@ -100,3 +100,5 @@ private:
  */
 int load_style(QString &path, QString &name);
 
+bool do_notify(QObject *receiver, QEvent *event);
+

src/calibre/gui2/progress_indicator/QProgressIndicator.sip

@@ -8,6 +8,7 @@
 
 %ModuleHeaderCode
 int load_style(QString &path, QString &name);
+bool do_notify(QObject *receiver, QEvent *event);
 %End
 
 class QProgressIndicator : QWidget {
@@ -57,3 +58,5 @@ protected:
 
 int load_style(QString &path, QString &name);
 
+bool do_notify(QObject *receiver, QEvent *event);
+