Saving map defaults to PNG instead of BMP

This only affects a user the first time they save a map as an image.
Afterwards their preference is saved.

FIXES: #8493

src/gui/qgisgui.cpp

@@ -93,7 +93,7 @@ namespace QgisGui
       if ( format ==  "svg" )
         continue;
 
-      filterMap.insert( createFileFilter_( format.toUpper() + " format", "*." + format ), format );
+      filterMap.insert( createFileFilter_( format ), format );
     }
 
 #ifdef QGISDEBUG
@@ -104,14 +104,13 @@ namespace QgisGui
     }
 #endif
 
-    //find out the last used filter
     QSettings settings;  // where we keep last used filter in persistent state
-    QString lastUsedFilter = settings.value( "/UI/lastSaveAsImageFilter" ).toString();
     QString lastUsedDir = settings.value( "/UI/lastSaveAsImageDir", "." ).toString();
 
-    QString outputFileName;
-    QString selectedFilter = lastUsedFilter;
-    QString ext;
+    // Prefer "png" format unless the user previously chose a different format
+    QString pngExtension = "png";
+    QString pngFilter = createFileFilter_( pngExtension );
+    QString selectedFilter = settings.value( "/UI/lastSaveAsImageFilter", pngFilter ).toString();
 
     QString initialPath;
     if ( defaultFilename.isNull() )
@@ -125,6 +124,8 @@ namespace QgisGui
       initialPath = QDir( lastUsedDir ).filePath( defaultFilename );
     }
 
+    QString outputFileName;
+    QString ext;
 #if defined(Q_OS_WIN) || defined(Q_OS_MAC) || defined(Q_OS_LINUX)
     outputFileName = QFileDialog::getSaveFileName( theParent, theMessage, initialPath, QStringList( filterMap.keys() ).join( ";;" ), &selectedFilter );
 
@@ -174,9 +175,9 @@ namespace QgisGui
     return qMakePair<QString, QString>( outputFileName, ext );
   }
 
-  QString createFileFilter_( QString const &longName, QString const &glob )
+  QString createFileFilter_( QString const &format )
   {
-    return longName + " (" + glob.toLower() + " " + glob.toUpper() + ")";
+    return QString( "%1 format (*.%2 *.%1)" ).arg( format.toUpper() ).arg( format.toLower() );
   }
 
 } // end of QgisGui namespace

src/gui/qgisgui.h

@@ -83,14 +83,12 @@ namespace QgisGui
   QPair<QString, QString> GUI_EXPORT getSaveAsImageName( QWidget * theParent, QString theMessage, QString defaultFilename = QString::null );
 
   /**
-    Convenience function for readily creating file filters.
-
-    Given a long name for a file filter and a regular expression, return
-    a file filter string suitable for use in a QFileDialog::OpenFiles()
-    call.  The regular express, glob, will have both all lower and upper
-    case versions added.
-  */
-  QString createFileFilter_( QString const &longName, QString const &glob );
+   * Create file filters suitable for use with QFileDialog
+   *
+   * @param format extension e.g. "png"
+   * @return QString e.g. "PNG format (*.png, *.PNG)"
+   */
+  QString createFileFilter_( QString const &format );
 }
 
 #endif