Marble/MarblePythonLayerInterface

    From KDE TechBase
    Revision as of 10:56, 30 December 2013 by Benjaminkaiser (talk | contribs)
    Drawing in Custom Layers
    Tutorial Series   Marble Python Tutorial
    Previous   Tutorial 13 - Painting onto the map
    What's Next   Tutorial 15 - Painting GeoDataLineString: Using the GeoPainter in order to paint a GeoDataLineString object
    Further Reading   n/a

    The previous tutorial showed how to override the customPaint() method in MarbleWidget to paint on top of the map. It is also possible to paint at different layer positions. This is similar to providing a z-order of elements being painted.

    To achieve this, we'll take a look at an example. Instead of deriving from MarbleWidget, we create our own Marble.LayerInterface class. After passing it to Marble, it will be included in painting similar to how customPaint() was called. This time however we are able to specify at which layer to paint.

    To illustrate the painting in different layers, the code below paints a clock and implements the ability to dynamically switch its layer position by pressing '+'. Notice how the current layer position is indicated in the window title. When painting in the "STARS" layer, you won't see anything -- we'll paint behind the map. In the "SURFACE" layer, city names and other placemarks will be painted on top of us. In contrast, "ORBIT" will make us paint over placemarks, while float items (info boxes) still paint above us. This will change when we paint in the "USER TOOLS" layer.

    #!/usr/bin/env python
    from PyQt4.QtCore import *
    from PyQt4.QtGui import *
    from PyKDE4.marble import *
    import sys
    from math import *
    
    class MyEventFilter(QObject):
        def __init__(self, painter, marble):
            QObject.__init__(self)
            self.painter = painter
            self.marble = marble
    
        def eventFilter(self, obj, event):
            if(event.type() == QEvent.KeyPress):
                if(event.key() == Qt.Key_Plus):
                    self.painter.m_index += 1
                    self.marble.update()
                    return True
            return False
    
    class MyPaintLayer(Marble.LayerInterface, QObject):
        def __init__(self, marble):
            QObject.__init__(self)
            self.marble = marble
            self.m_index = 0
    
        def renderPosition(self):
            layers = ['SURFACE', 'HOVERS_ABOVE_SURFACE', 'ORBIT', 'USER_TOOLS', 'STARS']
            index = self.m_index % len(layers)
            tmpList = [layers[index]]
            return tmpList
    
        def approximate(self, base, angle, dist):
            deg = Marble.GeoDataCoordinates.Degree
            return Marble.GeoDataCoordinates(
                base.longitude(deg) + 1.5 * dist * sin(angle),
                base.latitude(deg) + dist * cos(angle), 0.0, deg)
    
        def render(self, painter, viewPort, renderPos, layer):
            # have window title reflect the current paint layer
            self.marble.setWindowTitle(self.renderPosition()[0])
            home = Marble.GeoDataCoordinates(8.4, 48.0, 0.0, Marble.GeoDataCoordinates.Degree)
            now = QTime.currentTime()
            painter.setRenderHint(QPainter.Antialiasing, True)
         
            # large circle built by 60 small circles
            painter.setPen(QPen(QBrush(QColor.fromRgb(255,255,255,200)), 3.0, Qt.SolidLine, Qt.RoundCap))
            i=0
            while(i<60):
                painter.drawEllipse(self.approximate(home, pi * i / 30.0, 1.0), 5, 5)
                i += 1
            # hour, minute, second hand
            painter.setPen(QPen(QBrush(Qt.blue), 4.5, Qt.SolidLine, Qt.RoundCap))
            painter.drawEllipse(self.approximate(home, pi * now.minute() / 30.0, 1.0), 5, 5)
            painter.setPen(QPen(QBrush(Qt.green), 4.0, Qt.SolidLine, Qt.RoundCap))
            painter.drawEllipse(self.approximate(home, pi * now.hour() / 6.0, 1.0), 5, 5)
            painter.setPen(QPen(QBrush(Qt.red), 3.5, Qt.SolidLine, Qt.RoundCap ))
            painter.drawEllipse(self.approximate(home, pi * now.second() / 30.0, 1.0), 5, 5)
         
            return True;
    
    def main():
        app = QApplication(sys.argv)
    
        # create the marble widget
        marble = Marble.MarbleWidget()
    
        # resize the widget and add a window title
        marble.resize(500, 500)
    
        layer = MyPaintLayer(marble)
        marble.addLayer(layer)
        eventFilter = MyEventFilter(layer, marble)
        marble.installEventFilter(eventFilter)
    
        # Load the OpenStreetMap map
        marble.setMapThemeId("earth/bluemarble/bluemarble.dgml")
        marble.centerOn(Marble.GeoDataCoordinates(8.4, 49.0, 0.0, Marble.GeoDataCoordinates.Degree))
    
        # show the marble widget
        marble.show()
    
        # Update each second to give the clock second resolution
        seconds = QTimer()
        seconds.setInterval(1000)
        app.connect(seconds, SIGNAL('timeout()'), marble.update)
        seconds.start()
    
        # run the app
        app.exec_()
    
    main()
    

    Save the code above as layers.py and execute python layers.py and you end up with a globe view painting a slightly different interpretation of a world clock: