Difference between revisions of "Projects/Marble/MarbleGeoPainter"

Jump to: navigation, search
(Created page with 'In the previous tutorial, you saw how easy it is to embed a MarbleWidget in any Qt application: Just create a Marble::MarbleWidget, set a map theme on it and... you're done alrea...')
 
(13 intermediate revisions by 2 users not shown)
Line 1: Line 1:
In the previous tutorial, you saw how easy it is to embed a MarbleWidget in any Qt application: Just create a Marble::MarbleWidget, set a map theme on it and... you're done already.
 
  
Next we'll extend that example a bit and write our own little paint method to add some extra content to the globe. To facilitate this, Marble provides a painting hook called customPaint. It is called in between of the normal paint operations: After the background and tiles are painted, but before the top layers like float items (info boxes).
+
{{TutorialBrowser|
  
The customPaint operation is called with a GeoPainter: An extended QPainter which not only is able to paint at certain screen (pixel) positions, but also at certain geo (lat,lon) positions. We'll make use of that feature now. To keep things simple again, we just add a little 'Hello World' message indicated by a green circle.
+
series=Marble C++ Tutorial|
  
<code cppqt>
+
name=GeoPainter: Painting onto the map|
 +
 
 +
pre=[[Projects/Marble/MarbleSignalsSlots|Tutorial 3 - Basic interaction with MarbleWidget]]|
 +
 
 +
next=[[Projects/Marble/LayerInterface|Tutorial 5 - Drawing in Custom Layers]]|
 +
}}
 +
 
 +
In the previous tutorial you've seen how easy it is to embed a [http://api.kde.org/4.x-api/kdeedu-apidocs/marble/html/classMarble_1_1MarbleWidget.html MarbleWidget] into a Qt application: Just create a MarbleWidget, set a map theme on it and ... you're done already.
 +
 
 +
Next we'll extend that example a bit and write our own little paint method to add some extra content to the globe. To facilitate this, Marble provides a painting hook called [http://api.kde.org/4.x-api/kdeedu-apidocs/marble/html/classMarble_1_1MarbleWidget.html#47e87a8639f38e9da380923453a6f35f MarbleWidget::customPaint]. It is called in between of the normal paint operations: After the background and tiles are painted, but before the top layers like float items (info boxes).
 +
 
 +
The customPaint operation is called with a [http://api.kde.org/4.x-api/kdeedu-apidocs/marble/html/classMarble_1_1GeoPainter.html GeoPainter]: An extended [http://doc.trolltech.com/qpainter.html QPainter] which not only is able to paint at certain screen (pixel) positions, but also at certain geo (lat,lon) positions. We'll make use of that feature now. To keep things simple again, we just add a little 'Hello World' message indicated by a green circle.
 +
 
 +
<source lang="cpp">
 
#include <QtGui/QApplication>
 
#include <QtGui/QApplication>
 
#include <marble/MarbleWidget.h>
 
#include <marble/MarbleWidget.h>
Line 35: Line 47:
 
     return app.exec();
 
     return app.exec();
 
}
 
}
</code>
+
</source>
  
 
Save the code above as <tt>my_marble.cpp</tt> and compile it:
 
Save the code above as <tt>my_marble.cpp</tt> and compile it:
  
<code>
+
<source lang="bash">
 
  g++ -I /usr/include/qt4/ -o my_marble my_marble.cpp -lmarblewidget -lQtGui
 
  g++ -I /usr/include/qt4/ -o my_marble my_marble.cpp -lmarblewidget -lQtGui
</code>
+
</source>
  
 
If things go fine, execute <tt>./my_marble</tt> and you end up with a globe view similar to this:
 
If things go fine, execute <tt>./my_marble</tt> and you end up with a globe view similar to this:
 +
 
[[Image:Marble-geopainter.png]]
 
[[Image:Marble-geopainter.png]]
 +
 +
There may be situations where MarbleWidget::customPaint() does not suit your needs. This can be the case when you don't want to paint at the very top position (above all other items), or when subclassing MarbleWidget is not possible for some reason. In that case, have a look at the next chapter [[Projects/Marble/LayerInterface|Drawing in Custom Layers]]

Revision as of 16:25, 19 July 2012

GeoPainter: Painting onto the map
Tutorial Series   Marble C++ Tutorial
Previous   Tutorial 3 - Basic interaction with MarbleWidget
What's Next   Tutorial 5 - Drawing in Custom Layers
Further Reading   n/a

In the previous tutorial you've seen how easy it is to embed a MarbleWidget into a Qt application: Just create a MarbleWidget, set a map theme on it and ... you're done already.

Next we'll extend that example a bit and write our own little paint method to add some extra content to the globe. To facilitate this, Marble provides a painting hook called MarbleWidget::customPaint. It is called in between of the normal paint operations: After the background and tiles are painted, but before the top layers like float items (info boxes).

The customPaint operation is called with a GeoPainter: An extended QPainter which not only is able to paint at certain screen (pixel) positions, but also at certain geo (lat,lon) positions. We'll make use of that feature now. To keep things simple again, we just add a little 'Hello World' message indicated by a green circle.

#include <QtGui/QApplication>
#include <marble/MarbleWidget.h>
#include <marble/GeoPainter.h>
 
using namespace Marble;
 
class MyMarbleWidget : public MarbleWidget
{
public:
    virtual void customPaint(GeoPainter* painter);
};
 
void MyMarbleWidget::customPaint(GeoPainter* painter)
{
    GeoDataCoordinates home(8.4, 49.0, 0.0, GeoDataCoordinates::Degree);
    painter->setPen(Qt::green);
    painter->drawEllipse(home, 7, 7);
    painter->setPen(Qt::black);
    painter->drawText(home, "Hello Marble!");
}
 
int main(int argc, char** argv)
{
    QApplication app(argc,argv);
    MyMarbleWidget *mapWidget = new MyMarbleWidget;
    mapWidget->setMapThemeId("earth/openstreetmap/openstreetmap.dgml");
    mapWidget->show();
    return app.exec();
}

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

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

If things go fine, execute ./my_marble and you end up with a globe view similar to this:

Marble-geopainter.png

There may be situations where MarbleWidget::customPaint() does not suit your needs. This can be the case when you don't want to paint at the very top position (above all other items), or when subclassing MarbleWidget is not possible for some reason. In that case, have a look at the next chapter Drawing in Custom Layers


KDE® and the K Desktop Environment® logo are registered trademarks of KDE e.V.Legal