QTreeView questions

jim87

Hello!

I've got a couple of questions about QTreeView.

First things first: I'm using PySide6.

Currently I've got a QTreeView which loads a series of nested items. The first time it loads them, it works almost flawlessly: the thing that's not working is that it shows an empty row at the bottom which, if clicked, crashes the UI without any traceback.

If I don't touch the last row and try to update the model (by removing all the rows and filling it again with new rows), the application eats all the memory in a couple of seconds (something like... 32GB of RAM) and I'm forced to kill it.

I'm doing something wrong for sure.

This is the code I've written for it:

    def load_functions_from_project(self):
        logger = logging.getLogger(__name__)

        model = self.functionsTreeView.model()
        if not model:
            model = QStandardItemModel()
            self.functionsTreeView.setModel(model)

        self.functionsTreeView.setUpdatesEnabled(False)  # Attempt to optimize
        if model.hasChildren():
            model.removeRows(0, model.rowCount())  # here it eats all the memory and freezes

        if not self.project:
            return

        functions = self.project.functions  # just a dataclass
        functions.sort(key=lambda fn: f'{fn.module}{fn.name}')

        rootNode = model.invisibleRootItem()
        items: Dict[str, TreeItem] = {}
        for fn in functions:
            module_path = fn.module.split('.')  # a.b.c.d
            current_path = ''
            for path in module_path:
                previous_path = current_path
                if not previous_path:
                    current_path = path
                else:
                    current_path = '.'.join([current_path, path])
                if current_path not in items:
                    node = TreeItem(text=path)  # It's a subclass of QStandardItem which sets enabled, text, drag enabled
                    items[current_path] = node
                    if not previous_path:
                        rootNode.appendRow(node)
                    else:
                        items[previous_path].appendRow(node)
            node = TreeItem(text=fn.name, function=fn)
            items[fn.module].appendRow(node)

        model.appendRow(rootNode)
        self.functionsTreeView.setUpdatesEnabled(False)

        self.functionsTreeView.collapseAll()

May you please help me?

Thank you very much :)

SGaist

Hi and welcome to devnet,

@jim87 said in QTreeView questions:

model.removeRows(0, model.rowCount()) # here it eats all the memory and freezes

~~Aren't you removing one row too many ?~~

[edit: wrong function signature in mind SGaist]

JonB

@SGaist said in QTreeView questions:

Aren't you removing one row too many ?

Why do you say this? [Unless there is something about using a model for a QTreeView requiring one to preserve one item, but I'm not aware of that.]

[removeRows() takes a count of rows to remove, not an index-of-last-row if that's what you're thinking?]

jim87

@SGaist I tried replacing the whole model with, say, self.functionsTreeView.setModel(None) - same result of eating memory and freezing

JonB

@jim87
It's probably not relevant, but you leave treeview updates disabled. I assume your second

self.functionsTreeView.setUpdatesEnabled(False)

near the end is supposed to pass True. Correct that and/or comment out these "optimizations" while diagnosing the problem.

jim87

@JonB thanks to pointing that out. Unfortunately this did nothing about the problem.

I think we should concentrate on the empty item which shouldn't be there:

According to the code, there should be at least a Function with an empty 'module' attribute, but there isn't:

jim87

Ok, I've made a PoC for this issue, where both the "extra" tree element appears and when you try to load twice it will eat all the memory, freezing .

I'm running Python 3.10.1 with PySide6 6.2.2.1 under Linux Fedora 35.

I can't attach the zip file here, though you can download it from the following link: https://drive.google.com/file/d/1vBZDIAZGhnS_Gi-rFalpxZKgB5zqLh7a/view?usp=sharing

Thanks :)

EDIT: I finally caught the error! I was creating the model's root item and I was appending all the items in it, though I was also appending the root item to the model itself (see line 184 of the last example). It was as easy as that.

Thanks for the support though :)

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