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QArrow a widget similar to GtkArrow in PyQt

by mandel on February 17th, 2012

Recently in Ubuntu One we have been working or using PyQt for the UI of our application so that we could keep a smaller code base. While doing the move I noticed that we needed to have a widget similar to GtkArrow and to my surprise there is not one.

The following is a small implementation fo such a widget that might help other people that are in need of it. Even maybe someone that cares enough will write it in C++ and will propose it to Qt, sorry but I don’t have the time.

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from PyQt4.QtGui import QPainter, QStyle, QStyleOption, QWidget
 
 
class QArrow(QWidget):
    """Qt implementation similar to GtkArrow."""
 
   UP = 0
   DOWN = 1
   LEFT = 2
   RIGHT = 3
 
   def __init__(self, direction, parent=None):
       """Create a new instance."""
       QWidget.__init__(self, parent)
       if not direction in (QArrow.UP, QArrow.DOWN,
                 QArrow.LEFT, QArrow.RIGHT):
           raise ValueError('Wrong arrow direction.')
       self._direction = direction
 
    def paintEvent(self, event):
        """Paint a nice primitive arrow."""
        opt = QStyleOption()
        opt.initFrom(self)
        p = QPainter(self)
        if self._direction == QArrow.UP:
            primitive = QStyle.PE_IndicatorArrowUp
        elif self._direction == QArrow.DOWN:
            primitive = QStyle.PE_IndicatorArrowDown
        elif self._direction == QArrow.LEFT:
            primitive = QStyle.PE_IndicatorArrowLeft
        else:
            primitive = QStyle.PE_IndicatorArrowRight
        self.style().drawPrimitive(primitive, opt, p, self)

Took longer to think the correct way to do it than the actual coding, at the end is very simple.

From Canonical, Python