PyQt QCalendarWidget events question

[tinnews at isbd.co.uk]

John Posner <jjposner at optimum.net> wrote:
> On 7/16/2012 12:28 PM, tinnews at isbd.co.uk wrote:
> > tinnews at isbd.co.uk wrote:
> >> I am trying to use the PyQt4 calendar widget to perform some different
> >> actions on specific dates.  There are three events available:-
> >>
> >>     selectionChanged()
> >>     activated(QDate)
> >>     clicked(QDate)
> >>
> >> On trying all these out it would appear that the event handlers get
> >> called as follows:-
> >>
> >>     The clicked(QDate) event gets called if you click on an already
> >>     selected date.
> >>
> >>     The selectionChanged() and then the clicked(QDate) events are
> >>     called when you click on a new date.
> >>
> >>     The selectionChanged(), then the clicked(QDate) and then the
> >>     activated(QDate) events are called if you double-click on a new date.
> >>
> >>     The clicked(QDate) and then the activated(QDate) events are called
> >>     if you double-click on an already selected date.
> >>
> >>
> >> How can I get a single-click on a date to get 'Action1' and double-click
> >> on a date to get 'Action2'?
> > I'm sorry, this got sent a bit before I'd completed it.  The trouble
> > is that I want to run Action1 if I single-click on a date whether or
> > not it's a changed date and I want to run Action2 if I double-click on
> > a date whether or not it's a changed date.  However I don't see how I
> > can do this because of the order in which the event handlers are
> > called.
> >
> > Is there any way to manipulate this so I can get the result I want? 
> > At the moment the only way I can see to do it is to wait a while after
> > a click and then look at what actions occurred but this seems a real
> > bodge.
> 
> I suspect that the consensus would be "don't do that" -- having
> single-click and double click perform unrelated actions.

They're not actually unrelated, one will edit an existing entry in a
file for the given date, the other will add a new entry in the file
for that date.  I.e. single-click means open file at specified date,
double-click means open file at specified date and insert a new entry
for that date.


>                                                            But here's an
> implementation based on the advice at
> http://www.qtcentre.org/threads/7858-Double-Click-Capturing
> 
> (use Ctrl-Break to break out of the event loop)
> 
> import PyQt4.QtCore as C
> import PyQt4.QtGui as G
> 
> class Button(G.QPushButton):
>     def __init__(self, text):
>         G.QPushButton.__init__(self, text)
> 
>         # flag to suppress second mouseReleaseEvent
>         # in this double-click event sequence:
>         # 1. mousePressEvent
>         # 2. mouseReleaseEvent
>         # 3. mouseDoubleClickEvent
>         # 4. mouseReleaseEvent
>         self.double_clicked = False
> 
>     def mouseReleaseEvent(self, evt):
>         # executed for first mouseReleaseEvent
>         if not self.double_clicked:
>             self.first_click_timer = C.QTimer()
>             self.first_click_timer.setSingleShot(True)
>             # double-click must occur within 1/4 second of first-click
> release
>             self.first_click_timer.setInterval(250)
>             self.first_click_timer.timeout.connect(self.single_click_action)
>             self.first_click_timer.start()
>         # executed for second mouseReleaseEvent
>         else:
>             # reset the flag
>             self.double_clicked = False
> 
>     def single_click_action(self):
>         print "Performing single-click action"
> 
>     def mouseDoubleClickEvent(self, evt):
>         # suppress the single-click action; perform double-click action
> instead
>         self.first_click_timer.stop()
>         print "Performing double-click action"
> 
>         # prepare for second mouseReleaseEvent
>         self.double_clicked = True
> 
> # main program
> 
> app = G.QApplication([])
> button = Button("Click or double-click me")
> button.show()
> app.exec_()
> 
> 
Yes, thanks, though it is basically the bodge using timing that I was
trying to avoid.  It's so fundamental to most GUIs that single-click
and double-click allow one to do different things with the same object
I'm surprised that pyqt makes it so difficult to implement.

-- 
Chris Green