QListWidget with dynamic icons

Harry123 · wrote on 31 Mar 2016, 11:33

I would like to have a QListWidget with many items, each containing text and icon in the standard manner. The text identifies the icon, meaning that the icon can be retrieved by using the text as the key.

My problem is that retrieving the icons is a relatively slow operation. Setting up the QListWidget would be much faster if I could only supply the text-part when initially creating the QListWidgetItem, later adding the icons only for the items that are really going to be displayed.

Is there a method by which I could intercept the display of a QListWidgetItem and add the icon just before the item is displayed?

I know that I can do this using QListView, but QListWidget already does much of the needed work.

SGaist · wrote on 31 Mar 2016, 19:19

Hi,

What about delegating the icon load to anther thread and then signal a data change when they are ready ?

Harry123 · wrote on 31 Mar 2016, 19:43

I would really prefer to avoid creating icons that will never be looked at, if possible.
I might find myself creating 1000 icons, while the user will never look at more than the first few screens.

SGaist · 1 Apr 2016, 11:50

Sorry, I just saw that my suggestion is incomplete. Your model should be queried when needed for the icons so what I was suggesting is that when one is queried, you start loading it and then trigger the dataChanged signal.

Harry123 · wrote on 1 Apr 2016, 11:50

@SGaist

Could you please add more details about this procedure.
I never used model/view.

SGaist · 2 Apr 2016, 10:05

Which part would like to have more detail on ?

Harry123 · 4 Feb 2016, 10:06

@SGaist

I would prefer to use QListWidget, because it is much simpler than using model/view with which I have no experience.
I need some pointers as to what should be done - classes and functions to call.

I myself was thinking more in the direction of connecting to the vertical scrollbar of QListWidget and anticipating scrolls, but I'm not sure I would guess correctly from the scroll events exactly which items will be displayed.

SGaist · 4 Apr 2016, 10:45

If you use QListWidget then you don't have any control over the model so you won't be able to move the image loading part outside of it.

Harry123 · S SGaist 2 Apr 2016, 20:33

@SGaist

I have basically given up on using QListWidget that efficiently.

SGaist · 14 Apr 2016, 07:16

What option did you choose ?

Harry123 · S SGaist 4 Apr 2016, 19:40

@SGaist

I have divided the list into sections, and modified the UI to show only one section at a time.
This solved the performance problem (and maybe even made the UI more user-friendly).

SGaist · wrote on 14 Apr 2016, 09:48

It's good when it's more friendly :)