List performance Problem

[jerrygou007]

thank u for you guys to bring slint to the world.

we use rust+slint to build the software for windows

in our case,
we have a page to show chat sessions, supported by a slint listview, it looks like below.
everytime,when the new word is added to the screen (to the end of 4th item),
the whole page will badly flicker,especially when the content is more than one page screen.

the list is updated by the below code

rust

 let datas_model: std::rc::Rc<slint::VecModel<ChatItemData>> = std::rc::Rc::new(slint::VecModel::from(datas));
 ui.global::<Chat>().set_datas(datas_model.into());

slint

chat-lv := ListView {
                for data in Chat.datas : ListViewItem {
                    id: data.id;
                    head: data.head;
                    name: data.name;
                    content: data.content;
                    score: data.score;
                }
                visible: Chat.datas.length > 0;
                viewport-y: -self.viewport-height;
  }
export global Chat {
    in-out property <[ChatItemData]> datas: [  ];
}    

i dive into the slint source cod,bug there is no way for me to improve the performace,
is there any suggestion for me to fix it.
if the low performace is fact, hope you slint team can fix it.
the listview xp is usually the most important thinking point for us to choose a UI Framework.

[FloVanGH]

Hi,

thank you for your report.

ui.global::<Chat>().set_datas(datas_model.into());

It this the way you update the model if there are changes or is this only initial?

If you use that way to update the model, it will be reloaded completely each time what ends up in a bad performance.

What you can do instead is this:

data_model.push(ChatItemData { ... });

This updates the view only on the position of the new item.

If you want to change data on a specific position you can do this:

data_model.set_row_data(3, ChatItemData { ... });

I hope this will help you. Otherwise feel free to ask for more help any time.