Marble/MarbleSignalsSlots: Difference between revisions

Revision as of 10:15, 6 July 2010

Editing Projects/Marble/MarbleCPlusPlus

Basic interaction with MarbleWidget

Tutorial Series	Marble C++ Tutorial
Previous	C++, Qt
What's Next	Tutorial 4 - Marble's GeoPainter
Further Reading	n/a

Creating a window with controls

We'd like to add other widgets to our Marble window: A zoom slider and a label that shows the current mouse position.

In order to achieve this we need to create a vertical layout. Once done we add the slider and the label that we created to the layout. Also we zoom the globe to the slider's default value using the MarbleWidget::zoomView(int) method.

We want to center our globe onto South America. So we create a new GeoDataCoordinates object that takes the longitude and the latitude as a parameter and we call MarbleWidget::centerOn.

Finally we connect the signals and slots that MarbleWidget offers to the signals and slots of the slider and the label:

include <QtGui/QApplication>

include <QtGui/QLayout>
include <QtGui/QSlider>
include <QtGui/QLabel>

include <marble/MarbleWidget.h>

using namespace Marble;
int main(int argc, char** argv)
{

   QApplication app(argc,argv);
   QWidget *window = new QWidget;

   // Create a Marble QWidget without a parent
   MarbleWidget *mapWidget = new MarbleWidget();

   // Load the Plain map
   mapWidget->setMapThemeId("earth/plain/plain.dgml");

   // Hide the FloatItems: OverviewMap, ScaleBar and Compass
   mapWidget->setShowOverviewMap(false);
   mapWidget->setShowScaleBar(false);
   mapWidget->setShowCompass(false);

   // Set the map quality to gain speed
   mapWidget->setMapQuality( NormalQuality, Still );
   mapWidget->setMapQuality( LowQuality, Animation );
   
   // Create a horizontal zoom slider and set the default zoom
   QSlider * zoomSlider = new QSlider(Qt::Horizontal);
   zoomSlider->setMinimum( 1000 );
   zoomSlider->setMaximum( 2400 );
   
   mapWidget->zoomView( zoomSlider->value() );

   // Create a label to show the geodetic position
   QLabel * positionLabel = new QLabel();
   positionLabel->setSizePolicy( QSizePolicy::Preferred, QSizePolicy::Fixed );

   // Add all widgets to the vertical layout.
   QVBoxLayout *layout = new QVBoxLayout;
   layout->addWidget(mapWidget);
   layout->addWidget(zoomSlider);
   layout->addWidget(positionLabel);

   // Center the map onto a given position
   GeoDataCoordinates home(-60.0, -10.0, 0.0, GeoDataCoordinates::Degree);
   mapWidget->centerOn(home);
   
   // Connect the map widget to the position label.
   QObject::connect( mapWidget, SIGNAL( mouseMoveGeoPosition( QString ) ),
                     positionLabel, SLOT( setText( QString ) ) );

   // Connect the zoom slider to the map widget and vice versa.
   QObject::connect( zoomSlider, SIGNAL( valueChanged(int) ),
                     mapWidget, SLOT( zoomView(int) ) );
   QObject::connect( mapWidget, SIGNAL( zoomChanged(int) ),
                     zoomSlider, SLOT( setValue(int) ) );

   window->setLayout(layout);
   window->resize( 400, 300 );

   window->show();

   return app.exec();

}

Save the code above as marble_control.cpp and compile it:

g++ -I /usr/include/qt4/ -o marble_control marble_control.cpp -lmarblewidget -lQtGui

If things go fine, execute ./marble_control and you end up with a map application that displays our globe with a zoom slider below:

@@ Line 17: / Line 17: @@
 In order to achieve this we need to create a vertical layout. Once done we add the slider and the label that we created to the layout. Also we zoom the globe to the slider's default value using the [http://api.kde.org/4.x-api/kdeedu/marble/classMarble_1_1MarbleWidget.html#d49d8ab0be0721c579bb511bdda45829 MarbleWidget::zoomView(int)] method.
-We want to center our globe onto a place that is different from the default. So we create a new GeoDataCoordinates object that takes the longitude and the latitude as a parameter. In the next step MarbleWidget::centerOn is called.
+We want to center our globe onto South America. So we create a new GeoDataCoordinates object that takes the longitude and the latitude as a parameter and we call [http://api.kde.org/4.x-api/kdeedu/marble/classMarble_1_1MarbleWidget.html#7cda9942ead26d60c89a7b54a073a2fd MarbleWidget::centerOn].
+Finally we connect the [http://doc.trolltech.com/signalsandslots.html signals and slots] that MarbleWidget offers to the signals and slots of the slider and the label:
 <code cppqt>
@@ Line 51: / Line 52: @@
      mapWidget->setMapQuality( LowQuality, Animation );
-     // Set default zoom and create horizontal zoom slider
+     // Create a horizontal zoom slider and set the default zoom
      QSlider * zoomSlider = new QSlider(Qt::Horizontal);
      zoomSlider->setMinimum( 1000 );