Force C++ SortModel sorting re-evaluation

[mous16]

Hello everybody,
I'm trying to wrap my head around custom model implementation in Slint, using C++.

Let's say I have a simple project, with a Slint file like this:

// appwindow.slint

import {  ListView, VerticalBox, Switch } from "std-widgets.slint";

export component AppWindow inherits Window {
    in property <[int]> model;
    in-out property ascending <=> ascending-switch.checked;
    callback ascending-changed <=> ascending-switch.toggled;

    VerticalBox {
        ascending-switch := Switch {
            text: "Ascending";
        }

        ListView {
            for item in root.model: Text {
                text: item;
            }
        }
    }
}

On C++ side, this is the entire implementation:

// main.cpp

#include <memory>
#include <utility>

#include "appwindow.h"
#include "slint.h"

class MySortModel: public slint::SortModel<int>
{
    bool ascending{true};

    [[nodiscard]] auto sort(const int& first, const int& second) const -> bool
    {
        return ascending ? first < second : first >= second;
    }

  public:
    MySortModel(std::shared_ptr<Model<int>> source_model):
      slint::SortModel<int>{std::move(source_model),
                            [this](const int& first, const int& second) { return sort(first, second); }}
    { }

    [[nodiscard]] auto getAscending() const -> bool { return ascending; }

    void setAscending(bool value)
    {
        ascending = value;
        // Perform some kind of magic to force sorting re-evaluation
    }
};

auto main([[maybe_unused]] int argc, [[maybe_unused]] char** argv) -> int
{
    auto appWindow{AppWindow::create()};

    const auto model{std::make_shared<slint::VectorModel<int>>(std::vector<int>{1, 2, 3, 4, 5})};
    const auto sortModel{std::make_shared<MySortModel>(model)};

    appWindow->set_ascending(sortModel->getAscending());
    appWindow->set_model(sortModel);
    appWindow->on_ascending_changed([appWindow, sortModel]() { sortModel->setAscending(appWindow->get_ascending()); });

    appWindow->run();

    return 0;
}

Inside MySortModel::setAscending(bool), I need to notify the parent SortModel that the sorting function is changed, and sorting must be re-evaluated for every element in the underlying model.

How to achieve this behavior?

Reading the documentation, it seems that SortModel::reset() is the closest thing, but instead it triggers a call loop between SortModel::reset() and SortModelInner::reset().

Thanks in advance!

[ogoffart]

This is a bug in SortModelInner::reset()

[ogoffart]

Filled as an issue in #4968