[Qt-interest] QGraphicsItem and Threads

[Brad Howes]

On Oct 19, 2009, at 9:14 AM, Ole Streicher wrote:

> I am trying to change lots of QGraphicsItems at once:
>
> for item in self.items:
>    item.setBrush(QtGui.QBrush(QtGui.QColor(c[0], c[1], c[2]))

<snip>

> What is wron here? And how can I make huge graphical changes (100.000
> items) without getting my GUI unresponsive?


First, try to determine where the slow-down occurs. If the brush is  
the same for all of your objects, then it is a bit silly to have to  
create 100K brushes; adapt your objects to use a common brush instead.  
If not, try making the brush update an asynchronous signal/slot; that  
way, you remain response as the application tries to deliver the  
signal to the 100K objects. Also, try controlling the updates of the  
view. Check out the QGraphicsView API (viewportUpdateMode and  
optimization flags in particular).

Brad

-- 
Brad Howes
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