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  1. Qt
  2. QTBUG-94981

QTreeView: expandToDepth() and expandAll() ends prematurely for asynchronous models

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    Details

    • Platform/s:
      Linux/X11, Windows
    • Commits:
      f6bca6261156e8f648bf7d41ba1728ef17cd6889 (qt/qtbase/dev) ba0bca338c4fa743b007a4c4f204f09f9e5a8a80 (qt/tqtc-qtbase/5.15) 8df72123254277454f46945171194d1aa945b1d2 (qt/qtbase/6.1) 96222ec18c0e14995ae843cde9faf8a1b96d4943 (qt/qtbase/6.2)

      Description

      Issue

      When the model is asynchronous (like QFileSystemModel, or the example model at https://code.qt.io/cgit/qt/qtopcua.git/tree/examples/opcua/opcuaviewer ), expandToDepth() might stop expanding before the desired depth is reached.

      The same occurs with expandAll().

      Demo

      #include <QtWidgets>
      
      int main(int argc, char *argv[])
      {
      	QApplication a(argc, argv);
      
      	auto model = new QFileSystemModel;
      	model->setRootPath("C:/tmp");
      
      	QTreeView tree;
      	tree.setModel(model);
      
      	QPushButton button("Click me to expand");
      	QObject::connect(&button, &QPushButton::clicked, [&]{
      		tree.expandToDepth(3);
      	});
      
      	tree.show();
      	button.show();
      
      	return a.exec();
      }
      
      • Expected behaviour: 1 click should expand the tree to depth 3
      • Actual behaviour: Multiple clicks are required to reach depth 3 (Although depending on your filesystem size, the last click will likely freeze the app)

      Workaround

      Call `expandToDepth(depth)` repeatedly (with a slight wait between each call) until the desired depth is reached. Each call causes the model to fetch a bit more data, so it allows expansion to proceed a bit further.

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            People

            Assignee:
            vhilshei Volker Hilsheimer
            Reporter:
            skoh-qt Sze Howe Koh
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              Dates

              Created:
              Updated:
              Resolved:

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