= Making non-clickable widgets clickable =

On the `#pyqt` channel on Freenode, `xh` asked if it was possible to make QLabel objects clickable without subclassing.

There are two ways to do this:

 1. Use event filters.
 2. Assign new methods to the labels.

These are shown below.

== Event filters ==

The following example code shows how to use event filters to do this. It uses one filter object per label, which is created when the `clickable()` function is called with the widget that is to be click-enabled. The function returns a `clicked()` signal that actually belongs to the filter object. The caller can connect this signal to a suitable callable object.

{{{
#!python
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

def clickable(widget):

    class Filter(QObject):
    
        clicked = pyqtSignal()
        
        def eventFilter(self, obj, event):
        
            if obj == widget:
                if event.type() == QEvent.MouseButtonRelease:
                    if obj.rect().contains(event.pos()):
                        self.clicked.emit()
                        # The developer can opt for .emit(obj) to get the object within the slot.
                        return True
            
            return False
    
    filter = Filter(widget)
    widget.installEventFilter(filter)
    return filter.clicked


class Window(QWidget):

    def __init__(self, parent = None):
    
        QWidget.__init__(self, parent)
        
        label1 = QLabel(self.tr("Hello world!"))
        label2 = QLabel(self.tr("ABC DEF GHI"))
        label3 = QLabel(self.tr("Hello PyQt!"))
        
        clickable(label1).connect(self.showText1)
        clickable(label2).connect(self.showText2)
        clickable(label3).connect(self.showText3)
        
        layout = QHBoxLayout(self)
        layout.addWidget(label1)
        layout.addWidget(label2)
        layout.addWidget(label3)
    
    def showText1(self):
        print "Label 1 clicked"
    
    def showText2(self):
        print "Label 2 clicked"
    
    def showText3(self):
        print "Label 3 clicked"


if __name__ == "__main__":

    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())
}}}

== Assigning new methods ==

As `xh` pointed out, it should be possible to assign new event handler methods to instances of QLabel, and this should work as long as the labels were created in Python:

{{{
#!python

import sys
from PyQt4.QtGui import *

class Window(QWidget):

    def __init__(self, parent = None):
    
        QWidget.__init__(self, parent)
        
        label1 = QLabel(self.tr("Hello world!"))
        label2 = QLabel(self.tr("ABC DEF GHI"))
        label3 = QLabel(self.tr("Hello PyQt!"))
        
        label1.mouseReleaseEvent = self.showText1
        label2.mouseReleaseEvent = self.showText2
        label3.mouseReleaseEvent = self.showText3
        
        layout = QHBoxLayout(self)
        layout.addWidget(label1)
        layout.addWidget(label2)
        layout.addWidget(label3)
    
    def showText1(self, event):
        print "Label 1 clicked"
    
    def showText2(self, event):
        print "Label 2 clicked"
    
    def showText3(self, event):
        print "Label 3 clicked"


if __name__ == "__main__":

    app = QApplication(sys.argv)
    window = Window()
    window.show()
    sys.exit(app.exec_())
}}}