Repaint single item in QListView

nhunter

I have subclassed QListView and QAbstractItemModel to display a list of files in IconMode. I want to use a default icon when I create and populate the view. After the view is displayed, I want to use a worker thread to create an icon from each file and then update the icon in the list view. I can not figure out how to do this. I have got everything working except that the icons in the list view do not update until I swipe the mouse across or resize the view or otherwise trigger a repaint. Instead I want them to update as they are loaded.

Here's the domain class.

class ImageFile:

    def __init__(self, path: str):
        self._path = path
        self._icon = None
        
    def getIcon(self) -> QIcon:
        return self._icon if self._icon is not None else QIcon(r'resources\icons\ImageFileIcon.png')
        
    def loadIcon(self) -> None:
        self._icon = QIcon(self._path)

The model and view classes are boilerplate but I can post code if necessary.

Here's where I update the icons.

class MainWindow(QMainWindow):
    ...        
    def loadThumbnails(self):
        worker = Worker(self._imageFileListModel._data.loadIcons)
        worker.signals.progress.connect(self.workerProgress)
        worker.signals.finished.connect(self.workerFinished)
        self._threadpool.start(worker)
        
    def workerProgress(self, i):
        print('Loaded icon #%d' % i)
        
    def workerFinished(self):
        print('Finished loading icons')

I need some way to connect the ImageFile class and the representation in the list view, then I could perform the update in MainWindow.workerProgress method or maybe by emitting a signal in the ImageFile.loadIcon method. Is this is a job that could be performed by a delegate?

I'm stumped. Any suggestions gratefully received.

jeremy_k

Store the icons in the model as a DecorationRole. When the custom icon is ready, call setData(), and the view will update if that index is visible.

nhunter

@jeremy_k Thanks that worked great! I appreciate the helping hand.