Fix for #7458, project crashes when loaded from command line

- Image selection previews now load only on first expansion of parent group box
- Note: this is an OK fix for 2.0 release. One better solution noted here: http://hub.qgis.org/issues/7458#note-12

Author: dakcarto

src/app/composer/qgscomposer.cpp

@@ -1725,7 +1725,6 @@ void QgsComposer::showEvent( QShowEvent* event )
   if ( event->spontaneous() ) //event from the window system
   {
     restoreComposerMapStates();
-    initialiseComposerPicturePreviews();
   }
 
 #ifdef Q_WS_MAC
@@ -1967,14 +1966,6 @@ void QgsComposer::addComposerPicture( QgsComposerPicture* picture )
   }
 
   QgsComposerPictureWidget* pWidget = new QgsComposerPictureWidget( picture );
-  if ( isVisible() )
-  {
-    pWidget->addStandardDirectoriesToPreview();
-  }
-  else
-  {
-    mPicturePreviews.append( pWidget );
-  }
   mItemWidgetMap.insert( picture, pWidget );
 }
 
@@ -2198,7 +2189,6 @@ void QgsComposer::cleanupAfterTemplateRead()
   }
 
   restoreComposerMapStates();
-  initialiseComposerPicturePreviews();
 }
 
 void QgsComposer::on_mActionPageSetup_triggered()
@@ -2225,17 +2215,6 @@ void QgsComposer::restoreComposerMapStates()
   mMapsToRestore.clear();
 }
 
-void QgsComposer::initialiseComposerPicturePreviews()
-{
-  //create composer picture widget previews
-  QList< QgsComposerPictureWidget* >::iterator picIt = mPicturePreviews.begin();
-  for ( ; picIt != mPicturePreviews.end(); ++picIt )
-  {
-    ( *picIt )->addStandardDirectoriesToPreview();
-  }
-  mPicturePreviews.clear();
-}
-
 void QgsComposer::populatePrintComposersMenu()
 {
   mPrintComposersMenu->clear();

src/app/composer/qgscomposer.h

@@ -331,10 +331,6 @@ class QgsComposer: public QMainWindow, private Ui::QgsComposerBase
     //! Initially after reading from xml, states are set to rectangle to achieve faster project loading.
     void restoreComposerMapStates();
 
-    //! Fills icons into composer picture widgets
-    //! To make loading from project faster, the previews are generated when the composer becomes visible.
-    void initialiseComposerPicturePreviews();
-
     //! Create composer view and rulers
     void createComposerView();
 
@@ -375,7 +371,6 @@ class QgsComposer: public QMainWindow, private Ui::QgsComposerBase
 
     //! We load composer map content from project xml only on demand. Therefore we need to store the real preview mode type
     QMap< QgsComposerMap*, int > mMapsToRestore;
-    QList< QgsComposerPictureWidget* > mPicturePreviews;
 
     QDockWidget* mItemDock;
     QDockWidget* mUndoDock;

src/app/composer/qgscomposerpicturewidget.cpp

@@ -31,7 +31,7 @@
 #include <QSettings>
 #include <QSvgRenderer>
 
-QgsComposerPictureWidget::QgsComposerPictureWidget( QgsComposerPicture* picture ): QWidget(), mPicture( picture )
+QgsComposerPictureWidget::QgsComposerPictureWidget( QgsComposerPicture* picture ): QWidget(), mPicture( picture ), mPreviewsLoaded( false )
 {
   setupUi( this );
 
@@ -44,6 +44,11 @@ QgsComposerPictureWidget::QgsComposerPictureWidget( QgsComposerPicture* picture
 
   mPreviewListWidget->setIconSize( QSize( 30, 30 ) );
 
+  // mSearchDirectoriesGroupBox is a QgsCollapsibleGroupBoxBasic, so its collapsed state should not be saved/restored
+  mSearchDirectoriesGroupBox->setCollapsed( true );
+  // setup connection for loading previews on first expansion of group box
+  connect( mSearchDirectoriesGroupBox, SIGNAL( collapsedStateChanged( bool ) ), this, SLOT( loadPicturePreviews( bool ) ) );
+
   connect( mPicture, SIGNAL( itemChanged() ), this, SLOT( setGuiElementValues() ) );
   connect( mPicture, SIGNAL( rotationChanged( double ) ), this, SLOT( setGuiElementValues() ) );
 }
@@ -464,6 +469,8 @@ void QgsComposerPictureWidget::addStandardDirectoriesToPreview()
     addDirectoryToPreview( *userDirIt );
     mSearchDirectoriesComboBox->addItem( *userDirIt );
   }
+
+  mPreviewsLoaded = true;
 }
 
 bool QgsComposerPictureWidget::testSvgFile( const QString& filename ) const
@@ -485,12 +492,14 @@ bool QgsComposerPictureWidget::testImageFile( const QString& filename ) const
   return !formatName.isEmpty(); //file is in a supported pixel format
 }
 
-void QgsComposerPictureWidget::showEvent( QShowEvent * event )
+void QgsComposerPictureWidget::loadPicturePreviews( bool collapsed )
 {
-  Q_UNUSED( event );
-  refreshMapComboBox();
+  if ( mPreviewsLoaded )
+  {
+    return;
+  }
 
-  if ( mPreviewListWidget->count() == 0 )
+  if ( !collapsed ) // load the previews only on first parent group box expansion
   {
     mPreviewListWidget->hide();
     mPreviewsLoadingLabel->show();
@@ -500,6 +509,12 @@ void QgsComposerPictureWidget::showEvent( QShowEvent * event )
   }
 }
 
+void QgsComposerPictureWidget::showEvent( QShowEvent * event )
+{
+  Q_UNUSED( event );
+  refreshMapComboBox();
+}
+
 void QgsComposerPictureWidget::resizeEvent( QResizeEvent * event )
 {
   Q_UNUSED( event );

src/app/composer/qgscomposerpicturewidget.h

@@ -53,9 +53,18 @@ class QgsComposerPictureWidget: public QWidget, private Ui::QgsComposerPictureWi
   private slots:
     /**Sets the GUI elements to the values of mPicture*/
     void setGuiElementValues();
+    /** Load SVG and pixel-based image previews
+     * @param collapsed Whether the parent group box is collapsed
+     * @note added in 1.9
+     */
+    void loadPicturePreviews( bool collapsed );
 
   private:
     QgsComposerPicture* mPicture;
+    /** Whether the picture selection previews have been loaded
+     * @note added in 1.9
+     */
+    bool mPreviewsLoaded;
 
     /**Add the icons of a directory to the preview. Returns 0 in case of success*/
     int addDirectoryToPreview( const QString& path );

src/ui/qgscomposerpicturewidgetbase.ui

@@ -123,7 +123,7 @@
           <string notr="true">composeritem</string>
          </property>
          <property name="collapsed" stdset="0">
-          <bool>false</bool>
+          <bool>true</bool>
          </property>
          <layout class="QVBoxLayout" name="verticalLayout">
           <item>
@@ -133,11 +133,8 @@
               <italic>true</italic>
              </font>
             </property>
-            <property name="styleSheet">
-             <string notr="true">color: rgb(19, 133, 54);</string>
-            </property>
             <property name="text">
-             <string>Loading SVG previews...</string>
+             <string>Loading previews...</string>
             </property>
             <property name="alignment">
              <set>Qt::AlignCenter</set>