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Thread: QListView performance issue

  1. #1
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    Default QListView performance issue

    Hi,

    I have a tabbed application which one of them includes a QListView with custom item model & delegate. When application is minimized or maximized but one of the tabs which has no QListView in it is selected, CPU usage seems normal(about %6). But when I select a tab with a QListView, CPU usage rises to %30.

    I seems like my QListView drains too much CPU. I knew that listview is rendering continuously via delegate's paint method and most probably that causes this extensive CPU usage. Or am I wrong?

    I set my custom listview's setUniformItemSize to true but nothing changed.

    Any ideas?

    PS: I'm on Qt 4.8.

  2. #2
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    Default Re: QListView performance issue

    Listview does not coninuously render via the delegate if you don't explicitly tell it to by constantly updating the view.
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  3. #3
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    Default Re: QListView performance issue

    Ok then what could make it render continuously? Any suggestions for me to look at?

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    Default Re: QListView performance issue

    Do you call "repaint()" manually anywhere in your code ?

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    Default Re: QListView performance issue

    Is your custom model emitting signals that would cause the list view to reload its contents when the tab is clicked? In particular, if beginInsertRows() / endInsertRows() is happening for every row in the model, this could do it. The list would have to repaint itself for every row.

  6. #6
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    Default Re: QListView performance issue

    Do you call "repaint()" manually anywhere in your code ?
    Thanks for the suggestion but I've already checked it.

    In particular, if beginInsertRows() / endInsertRows() is happening for every row in the model, this could do it. The list would have to repaint itself for every row.
    Yes actually I use them just before adding a new listitem to the list(as well as I use beginRemoveRows / endRemoveRows when removing a list item). But I thought I must sort of use them. Isn't it so?

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    Default Re: QListView performance issue

    Do you have a custom delegate? Can you show us its code?
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  8. #8
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    Default Re: QListView performance issue

    Ok guys I found my silly mistake. I was setting style sheet in paintEvent function. Sorry to waste your time. Thank you.

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