Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-23 Thread Devon 
  Here is a dummy version of a derived tree widget:
 
  
  class MyTreeWidget(QTreeWidget):
  def __init__(self, parent=None):
  QTreeWidget.__init__(self, parent)
 
  def paintEvent(self, e):
  QTreeWidget.paintEvent(self, e)
  painter = QPainter(self)
  painter.end()
  
 
 
  When an instance is added to a layout, I get the following:
 
  
  QPainter::begin: Widget painting can only begin as a result of a paintEvent
  QPainter::end: Painter not active, aborted
  
 
  Any ideas what is causing the the painter to think it's not actually
  in a paintEvent?
 
  I'm using Qt 4.3.1, PyQt 4.3 and SIP 4.7

 The first thing to look at is whether e is a paint event or not:



Yes, it is a paint event.  I'm also not calling paintEvent()
explicitly anywhere - it's just being triggered off the main loop.
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Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-23 Thread David Boddie 
On Wed Aug 22 21:49:05 BST 2007, Devon wrote:

 Here is a dummy version of a derived tree widget:

[...]

 def paintEvent(self, e):
 QTreeWidget.paintEvent(self, e)
 painter = QPainter(self)
 painter.end()

[...]

 When an instance is added to a layout, I get the following:
 
 
 QPainter::begin: Widget painting can only begin as a result of a paintEvent
 QPainter::end: Painter not active, aborted
 
 
 Any ideas what is causing the the painter to think it's not actually
 in a paintEvent?

If you pass a device (self in this case) when you create a QPainter, don't
call its begin() or end() methods. I think its the end() call that actually
triggers this message in this case.

David
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Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-23 Thread Devon 
 If you pass a device (self in this case) when you create a QPainter, don't
 call its begin() or end() methods. I think its the end() call that actually
 triggers this message in this case.


I'm not explicitly calling begin() - I believe that's happening in
QPainter(self).  painter.end() is not the root cause.

this script produces the issue if anyone wants to try it:

-
import sys
from PyQt4.QtCore import *
from PyQt4.QtGui import *

class MyTreeWidget(QTreeWidget):
def __init__(self, parent=None):
QTreeWidget.__init__(self, parent)
def paintEvent(self, e):
QTreeWidget.paintEvent(self, e)
painter = QPainter(self)

if __name__ == __main__:
app = QApplication(sys.argv)
tree = MyTreeWidget()
tree.show()
sys.exit(app.exec_())
-

Outputs:
QPainter::begin: Widget painting can only begin as a result of a paintEvent
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Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-23 Thread David Boddie 
On Thu Aug 23 16:04:19 BST 2007, Devon wrote:

  If you pass a device (self in this case) when you create a QPainter, don't
  call its begin() or end() methods. I think its the end() call that
  actually triggers this message in this case.
 
 I'm not explicitly calling begin() - I believe that's happening in 
 QPainter(self).  painter.end() is not the root cause.

OK. I just noticed the use of an explicit end() without an explicit begin()
and jumped to conclusions about the cause of the problem. Sorry about that.

Anyway, it looks like we're trying to paint onto the wrong device - the
QAbstractScrollArea documentation for its paintEvent() method says this:

  This event handler can be reimplemented in a subclass to receive paint
  events (passed in event), for the viewport() widget.

  Note: If you open a painter, make sure to open it on the viewport().

So you write your paintEvent() to do this instead:

def paintEvent(self, e):
QTreeWidget.paintEvent(self, e)
painter = QPainter(self.viewport())

David
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Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-23 Thread Devon 
On 8/23/07, David Boddie [EMAIL PROTECTED] wrote:
 On Thu Aug 23 16:04:19 BST 2007, Devon wrote:

   If you pass a device (self in this case) when you create a QPainter, don't
   call its begin() or end() methods. I think its the end() call that
   actually triggers this message in this case.
 
  I'm not explicitly calling begin() - I believe that's happening in
  QPainter(self).  painter.end() is not the root cause.

 OK. I just noticed the use of an explicit end() without an explicit begin()
 and jumped to conclusions about the cause of the problem. Sorry about that.

 Anyway, it looks like we're trying to paint onto the wrong device - the
 QAbstractScrollArea documentation for its paintEvent() method says this:

   This event handler can be reimplemented in a subclass to receive paint
   events (passed in event), for the viewport() widget.

   Note: If you open a painter, make sure to open it on the viewport().

 So you write your paintEvent() to do this instead:

 def paintEvent(self, e):
 QTreeWidget.paintEvent(self, e)
 painter = QPainter(self.viewport())

 David


Perfect.  Thanks for your help!

~ Devon
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[PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-22 Thread Devon 
Hi, folks -

Here is a dummy version of a derived tree widget:


class MyTreeWidget(QTreeWidget):
def __init__(self, parent=None):
QTreeWidget.__init__(self, parent)

def paintEvent(self, e):
QTreeWidget.paintEvent(self, e)
painter = QPainter(self)
painter.end()



When an instance is added to a layout, I get the following:


QPainter::begin: Widget painting can only begin as a result of a paintEvent
QPainter::end: Painter not active, aborted


Any ideas what is causing the the painter to think it's not actually
in a paintEvent?

I'm using Qt 4.3.1, PyQt 4.3 and SIP 4.7

Thanks
~ Devon
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Re: [PyQt] can't create a QPainter in QTreeWidget's paintEvent

2007-08-22 Thread Jim Bublitz 
On Wednesday 22 August 2007 13:49, Devon wrote:
 Hi, folks -

 Here is a dummy version of a derived tree widget:

 
 class MyTreeWidget(QTreeWidget):
 def __init__(self, parent=None):
 QTreeWidget.__init__(self, parent)

 def paintEvent(self, e):
 QTreeWidget.paintEvent(self, e)
 painter = QPainter(self)
 painter.end()
 


 When an instance is added to a layout, I get the following:

 
 QPainter::begin: Widget painting can only begin as a result of a paintEvent
 QPainter::end: Painter not active, aborted
 

 Any ideas what is causing the the painter to think it's not actually
 in a paintEvent?

 I'm using Qt 4.3.1, PyQt 4.3 and SIP 4.7

The first thing to look at is whether e is a paint event or not:

if e.type () == QEvent.Paint:
print Paint Event
else:
print not Paint Event, e.type ()

The values for e.type () are on the QEvent page in the Qt docs.

Jim
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