Workaround for bug in Qt 5 that causes crashes if QDesktopServices is used before constructing a QApplication

src/calibre/gui2/__init__.py

@@ -1032,6 +1032,9 @@ class SanitizeLibraryPath(object):
                 os.environ[var] = orig
 
 def open_url(qurl):
+    # Qt 5 requires QApplication to be constructed before trying to use
+    # QDesktopServices::openUrl()
+    ensure_app()
     if isinstance(qurl, basestring):
         qurl = QUrl(qurl)
     with SanitizeLibraryPath():
@@ -1057,6 +1060,14 @@ def open_local_file(path):
         url = QUrl.fromLocalFile(path)
         open_url(url)
 
+def ensure_app():
+    global _store_app
+    if _store_app is None and QApplication.instance() is None:
+        args = sys.argv[:1]
+        if islinux or isbsd:
+            args += ['-platformpluginpath', sys.extensions_location, '-platform', 'headless']
+        _store_app = QApplication(args)
+
 def must_use_qt():
     ''' This function should be called if you want to use Qt for some non-GUI
     task like rendering HTML/SVG or using a headless browser. It will raise a
@@ -1064,11 +1075,7 @@ def must_use_qt():
     thread is not the main GUI thread. On linux, it uses a special QPA headless
     plugin, so that the X server does not need to be running. '''
     global gui_thread, _store_app
-    if _store_app is None and QApplication.instance() is None:
+    ensure_app()
-        args = sys.argv[:1]
-        if islinux or isbsd:
-            args += ['-platformpluginpath', sys.extensions_location, '-platform', 'headless']
-        _store_app = QApplication(args)
     if gui_thread is None:
         gui_thread = QThread.currentThread()
     if gui_thread is not QThread.currentThread():

src/calibre/headless/headless_integration.cpp

@@ -25,6 +25,8 @@ HeadlessIntegration::HeadlessIntegration(const QStringList &parameters)
 
     screenAdded(mPrimaryScreen);
     m_fontDatabase.reset(new QFontconfigDatabase());
+
+    platform_services.reset(new QGenericUnixServices());
 }
 
 HeadlessIntegration::~HeadlessIntegration()

src/calibre/headless/headless_integration.h

@@ -2,6 +2,8 @@
 
 #include <qpa/qplatformintegration.h>
 #include <qpa/qplatformscreen.h>
+#include <qpa/qplatformservices.h>
+#include <QtPlatformSupport/private/qgenericunixservices_p.h>
 #include <QScopedPointer>
 
 QT_BEGIN_NAMESPACE
@@ -41,8 +43,11 @@ public:
 
     static HeadlessIntegration *instance();
 
+    virtual QPlatformServices *services() const { return platform_services.data(); }
+
 private:
     QScopedPointer<QPlatformFontDatabase> m_fontDatabase;
+    QScopedPointer<QPlatformServices> platform_services;
 };
 
 QT_END_NAMESPACE