Infrastructure for dynamically loading Qt style plugins from python

src/calibre/gui2/progress_indicator/QProgressIndicator.cpp

@@ -1,6 +1,10 @@
 #include "QProgressIndicator.h"
 
 #include <QPainter>
+#include <QStylePlugin>
+#include <QPluginLoader>
+#include <QStyle>
+#include <QApplication>
 
 QProgressIndicator::QProgressIndicator(QWidget* parent, int size)
         : QWidget(parent),
@@ -122,3 +126,22 @@ void QProgressIndicator::paintEvent(QPaintEvent * /*event*/)
         p.restore();
     }
 }
+
+int load_style(QString &path, QString &name) {
+    int ret = 0;
+    QStyle *s;
+    QPluginLoader pl(path);
+    QObject *o = pl.instance();
+    if (o != 0) {
+        QStylePlugin *sp = qobject_cast<QStylePlugin *>(o);
+        if (sp != 0) {
+            s = sp->create(name);
+            if (s != 0) {
+                s->setObjectName(name);
+                QApplication::setStyle(s);
+                ret = 1;
+            }
+        }
+    }
+    return ret;
+}

src/calibre/gui2/progress_indicator/QProgressIndicator.h

@@ -91,3 +91,12 @@ private:
     QColor m_color;
 };
 
+/* Utility function that can be used to load a QStyle from a Qt plugin. This is
+ * here so that there is no need to create a separate PyQt plugin just for this
+ * simple functionality. 
+ * \param path The full path to the DLL containing the plugin
+ * \param name The name of the style plugin to load
+ * \return 1 if succeeds 0 otherwise. The objectName of the loaded style is set to name
+ */
+int load_style(QString &path, QString &name);
+

src/calibre/gui2/progress_indicator/QProgressIndicator.sip

@@ -6,6 +6,10 @@
 %Import QtCore/QtCoremod.sip
 %Import QtGui/QtGuimod.sip
 
+%ModuleHeaderCode
+int load_style(QString &path, QString &name);
+%End
+
 class QProgressIndicator : QWidget {
 
 %TypeHeaderCode
@@ -50,3 +54,6 @@ protected:
     virtual void paintEvent(QPaintEvent * event);
 
 };
+
+int load_style(QString &path, QString &name);
+