Implement BackendInterface to allow a choice of backends at run-time

 - New backends should implement BackendInterface
 - Use the interfaces to create new documents by means of the newDocument() method

PDFViewer.cpp

@@ -6,6 +6,14 @@ PDFViewer::PDFViewer(const QString pdf_doc, QWidget *parent, Qt::WindowFlags fla
   QtPDF::PDFDocumentWidget *docWidget = new QtPDF::PDFDocumentWidget(this);
   connect(this, SIGNAL(switchInterfaceLocale(QLocale)), docWidget, SLOT(switchInterfaceLocale(QLocale)));
 
+#ifdef USE_MUPDF
+  docWidget->setDefaultBackend(QString::fromAscii("mupdf"));
+#elif USE_POPPLER
+  docWidget->setDefaultBackend(QString::fromAscii("poppler-qt4"));
+#else
+  #error At least one backend is required
+#endif
+
   if (!pdf_doc.isEmpty() && docWidget)
     docWidget->load(pdf_doc);
   docWidget->goFirst();

src/PDFBackend.h

@@ -612,8 +612,20 @@ class Page
 
 } // namespace Backend
 
+class BackendInterface : public QObject
+{
+  Q_OBJECT
+public:
+  virtual ~BackendInterface() { }
+  virtual QSharedPointer<Backend::Document> newDocument(const QString & fileName) = 0;
+  virtual QString name() const = 0;
+  virtual bool canHandleFile(const QString & fileName) = 0;
+};
+
 } // namespace QtPDF
 
+Q_DECLARE_INTERFACE(QtPDF::BackendInterface, "org.tug.QtPDF/1.0")
+
 // Backend Implementations
 // =======================
 // These provide library-specific concrete impelemntations of the abstract base

src/PDFDocumentWidget.cpp

@@ -18,17 +18,29 @@ namespace QtPDF {
 PDFDocumentWidget::PDFDocumentWidget(QWidget * parent /* = NULL */)
 : PDFDocumentView(parent)
 {
+#ifdef USE_MUPDF
+  _backends.append(new MuPDFBackend());
+#endif
+#ifdef USE_POPPLER
+  _backends.append(new PopplerQt4Backend());
+#endif
 }
 
 PDFDocumentWidget::~PDFDocumentWidget()
 {
+  foreach(BackendInterface * bi, _backends) {
+    if (!bi)
+      continue;
+    bi->deleteLater();
+  }
 }
 
 // Loads the file specified by filename. If this succeeds, the new file is
 // displayed and true is returned. Otherwise, the view is not altered and false
 // is returned
 bool PDFDocumentWidget::load(const QString &filename)
 {
+/*
   // *TODO*: If more than one backend is available, maybe let users set their
   //          preferred one
 #ifdef USE_MUPDF
@@ -38,6 +50,14 @@ bool PDFDocumentWidget::load(const QString &filename)
 #else
   #error Either the Poppler or the MuPDF backend is required
 #endif
+*/
+  QSharedPointer<QtPDF::Backend::Document> a_pdf_doc;
+  foreach(BackendInterface * bi, _backends) {
+    if (bi && bi->canHandleFile(filename))
+      a_pdf_doc = bi->newDocument(filename);
+    if (a_pdf_doc)
+      break;
+  }
 
   if (!a_pdf_doc || !a_pdf_doc->isValid())
     return false;
@@ -52,4 +72,35 @@ bool PDFDocumentWidget::load(const QString &filename)
   return true;
 }
 
+QStringList PDFDocumentWidget::backends() const
+{
+  QStringList retVal;
+  foreach (BackendInterface * bi, _backends) {
+    if (bi)
+      continue;
+    retVal << bi->name();
+  }
+  return retVal;
+}
+
+QString PDFDocumentWidget::defaultBackend() const
+{
+  if (_backends.size() == 0)
+    return QString();
+  return _backends[0]->name();
+}
+
+void PDFDocumentWidget::setDefaultBackend(const QString & backend)
+{
+  int i;
+  for (i = 0; i < _backends.size(); ++i) {
+    if (_backends[i]->name() == backend)
+      break;
+  }
+  if (i < _backends.size()) {
+    _backends.move(i, 0);
+  }
+}
+
+
 } // namespace QtPDF

src/PDFDocumentWidget.h

@@ -30,10 +30,15 @@ class PDFDocumentWidget : public PDFDocumentView
   bool watchForDocumentChangesOnDisk() const { return _scene->watchForDocumentChangesOnDisk(); }
   void setWatchForDocumentChangesOnDisk(const bool doWatch = true) { _scene->setWatchForDocumentChangesOnDisk(doWatch); }
 
+  QStringList backends() const;
+  QString defaultBackend() const;
+  void setDefaultBackend(const QString & backend);
+
   // *TODO*: Possibly add some way to describe/choose/change the PDF backend used
 
 protected:
   QSharedPointer<QtPDF::PDFDocumentScene> _scene;
+  QList<BackendInterface*> _backends;
 };
 
 } // namespace QtPDF

src/backends/MuPDFBackend.h

@@ -21,6 +21,8 @@
 #ifndef MuPDFBackend_H
 #define MuPDFBackend_H
 
+#include "PDFBackend.h"
+
 extern "C"
 {
 #include <fitz.h>
@@ -127,6 +129,22 @@ class Page: public Backend::Page
 
 } // namespace Backend
 
+class MuPDFBackend : public BackendInterface
+{
+  Q_OBJECT
+  Q_INTERFACES(QtPDF::BackendInterface)
+public:
+  MuPDFBackend() { }
+  virtual ~MuPDFBackend() { }
+
+  virtual QSharedPointer<Backend::Document> newDocument(const QString & fileName) {
+    return QSharedPointer<Backend::Document>(new Backend::MuPDF::Document(fileName));
+  }
+
+  virtual QString name() const { return QString::fromAscii("mupdf"); }
+  virtual bool canHandleFile(const QString & fileName) { return QFileInfo(fileName).suffix() == QString::fromAscii("pdf"); }
+};
+
 } // namespace QtPDF
 
 #endif // End header guard

src/backends/PopplerBackend.h

@@ -21,6 +21,7 @@
 #ifndef PopplerBackend_H
 #define PopplerBackend_H
 
+#include "PDFBackend.h"
 #include <poppler/qt4/poppler-qt4.h>
 
 namespace QtPDF {
@@ -110,6 +111,22 @@ class Page: public Backend::Page
 
 } // namespace Backend
 
+class PopplerQt4Backend : public BackendInterface
+{
+  Q_OBJECT
+  Q_INTERFACES(QtPDF::BackendInterface)
+public:
+  PopplerQt4Backend() { }
+  virtual ~PopplerQt4Backend() { }
+
+  virtual QSharedPointer<Backend::Document> newDocument(const QString & fileName) {
+    return QSharedPointer<Backend::Document>(new Backend::Poppler::Document(fileName));
+  }
+
+  virtual QString name() const { return QString::fromAscii("poppler-qt4"); }
+  virtual bool canHandleFile(const QString & fileName) { return QFileInfo(fileName).suffix() == QString::fromAscii("pdf"); }
+};
+
 } // namespace QtPDF
 
 #endif // End header guard