The formatting and indents are all messed up on that gist. But it doesn't
look like you are doing much of anything in the paint event. Is it slow to
add them to the scene, or slow when you have 1000 of them and are just
moving them around?
One thing I can see is that it may be related to the sheer number of
individual svg images being loaded. What you might want to do is share a
renderer for svgs that you constantly load. For instance, you have the
common ":/Scene_ConnectNode.svg" image being loaded multiple times for
every GSceneItem; once for the output and then N number of input keyItems.
What you could do is create just one renderer for it and store it on the
scene or whereever, and then set that renderer on every new Connectionitem:
##
self._connRenderer = QSvgRenderer(':/Scene_ConnectNode.svg')
...
inputNode = ConnectionItem(self)
inputNode.setSharedRenderer(self._connRenderer)
self.inputNode[key] = inputNode
...
outputNode = ConnectionItem(self)
outputNode.setSharedRenderer(self._connRenderer)
self.outputNode = outputNode
##
You could also do the same for your node.sceneImage paths if they are a
common set. Keep a dictionary of renderers mapping to the path, and set the
shared renderer on each one. This might greatly reduce the number of times
you are loading this into memory. Though for all I know, Qt might be doing
some smart caching under the hood. But if its anything similar to QPixmaps,
this would work. I do the same with QPixmapCache, to cache the same path
instead of loading a new one for each.
Also the docs say that by default caching is enabled so you shouldnt have
to mess with any of that to get performance.
On Wed, Apr 3, 2013 at 6:33 PM, Tuan Nguyen <[email protected]> wrote:
> The first thing i had found out is the svg image i use for GraphicsItem is
> too complicate, after i remove all the detail from it, it runs a little
> smoothly but thousands of items O.O, i can't even imagine it. Here is the
> class of GraphicsItem i used
>
> https://gist.github.com/illunara/5298674
>
> Thanks for reply
>
>
> On Wed, Apr 3, 2013 at 6:04 AM, Judah Baron <[email protected]> wrote:
>
>> Yeah, that sounds suspicious. What's going on with those 20 items?
>>
>>
>> On Tue, Apr 2, 2013 at 11:07 AM, Justin Israel <[email protected]>wrote:
>>
>>> 20 items is by no means "a lot". I have had scenes with thousands of
>>> items. It sounds like you might be doing something heavy in your paint
>>> events.
>>> Can you provide some more details about the items you are using?
>>> Snippet?
>>> On Apr 3, 2013 1:01 AM, "illunara" <[email protected]> wrote:
>>>
>>>> Hi everybody
>>>> I'm working with QGraphicsView for a while, and after had finished
>>>> some basic stuff, i realized it gets slow down when there are a lot of
>>>> items (around 20, and it will freeze).
>>>>
>>>> When i set cacheMode in QGraphicsItem to ItemCoordinateCache which
>>>> will block the paintEvent, the performance is improve. So i guess that is
>>>> the cause. However, i don't know how to solve this yet :(
>>>>
>>>> Thanks
>>>>
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