What are you trying to achieve? Generally, adding as many widgets as possible to a root container of a view is not always the best option. Try bundling some lines together in a container. Maybe you really don't need a canvas line with antialiasing but can create a custom widget that implements ::draw() and writes pixels directly into the farmebuffer.
thank you for replying. I like your idea "create a custom widget that implements ::draw() and writes pixels directly into the farmebuffer", but I don't know how to do that. Can you help me ?