[Qt] Tree Widget #4112

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corranwebster wants to merge 13 commits into beeware:main from corranwebster:qt-tree

+478 −6

changes/3914.feature.18.md

Original file line number	Diff line number	Diff line change
		@@ -0,0 +1 @@
		The Tree widget is now supported in the Qt backend.

docs/en/reference/data/apis_by_platform.yaml

-Original file line number
+Diff line change
@@ Expand Up / @@ -194,7 +194,6 @@ Widgets: @@
           - android
           - web
           - textual
-          - qt
       WebView:
         description: An embedded web browser.
@@ Expand Down @@

docs/en/reference/images/tree-qt.png

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examples/tree/tree/app.py

-Original file line number
+Diff line change
@@ Expand Up / @@ -64,7 +64,7 @@ def on_select_handler(self, widget): @@
         # Button callback functions
         def insert_handler(self, widget, **kwargs):
             item = choice(bee_movies)
-            if year := item["year"] >= 2000:
+            if (year := item["year"]) >= 2000:
                 root = self.decade_2000s
             elif year >= 1990:
                 root = self.decade_1990s
@@ Expand Down @@

qt/src/toga_qt/factory.py

-Original file line number
+Diff line change
@@ Expand Up / @@ -32,6 +32,7 @@ @@
         from .widgets.table import Table
         from .widgets.textinput import TextInput
         from .widgets.timeinput import TimeInput
+        from .widgets.tree import Tree
         from .widgets.webview import WebView
         from .window import MainWindow, Window
     except ModuleNotFoundError as exc:  # pragma: no cover
@@ Expand Down Expand Up / @@ -76,6 +77,7 @@ @@
         "Table",
         "TextInput",
         "TimeInput",
+        "Tree",
         "WebView",
         "ImageView",
         "dialogs",
@@ Expand Down @@

qt/src/toga_qt/widgets/tree.py

-Original file line number
+Diff line change
@@ -0,0 +1,341 @@
+    import logging
+    import warnings
+    from typing import Any
+    from PySide6.QtCore import QAbstractItemModel, QModelIndex, QPersistentModelIndex, Qt
+    from PySide6.QtWidgets import QHeaderView, QTreeView
+    from travertino.size import at_least
+    from toga.sources import ListSource
+    from .base import Widget
+    logger = logging.getLogger(__name__)
+    # convenience root/invalid index object
+    INVALID_INDEX = QModelIndex()
+    class TreeSourceModel(QAbstractItemModel):
+        def __init__(self, source, columns, missing_value, **kwargs):
+            super().__init__(**kwargs)
+            self._source = source
+            self._columns = columns
+            self._missing_value = missing_value
+            # cache of id(node): node
+            # It's safe to use id() as the key, as the id can't be reused
+            # by Python for another object unless we remove the object from
+            # the cache
+            self._node_cache = {}
+        def set_source(self, source):
+            self.beginResetModel()
+            self._source = source
+            # Clear the cache, safe to do so here
+            self._node_cache = {}
+            self.endResetModel()
+        def reset_source(self):
+            self.beginResetModel()
+            # Clear the cache, safe to do so here
+            self._node_cache = {}
+            self.endResetModel()
+        def insert_item(self, index, item, parent=None):
+            if parent is None:
+                model_index = INVALID_INDEX
+            else:
+                model_index = self._get_index(parent)
+            self.beginInsertRows(model_index, index, index)
+            # Nothing to do, insertion has already happened
+            self.endInsertRows()
+        def remove_item(self, index, item, parent=None):
+            if parent is None:
+                model_index = INVALID_INDEX
+            else:
+                model_index = self._get_index(parent)
+            self.beginRemoveRows(model_index, index, index)
+            # remove item from cache: safe to do so now
+            self._node_cache.pop(id(item), None)
+            self.endRemoveRows()
+        def item_changed(self, item):
+            if self._source is None:
+                # The source can briefly be None during widget creation
+                return  # pragma: no cover
+            start_index = self._get_index(item)
+            end_index = self.index(
+                start_index.row(), len(self._columns) - 1, start_index.parent()
+            )
+            self.dataChanged.emit(start_index, end_index)
+        def _get_index(self, node, column=0) -> QModelIndex:
+            if self._source is None or not hasattr(node, "_parent"):
+                # The source can briefly be None during widget creation
+                # and bad user implementations of nodes could lead here.
+                return INVALID_INDEX  # pragma: no cover
+            rows = []
+            while node._parent is not None:
+                rows.append(node._parent.index(node))
+                node = node._parent
+            index = self.index(self._source.index(node), column, INVALID_INDEX)
+            while rows:
+                index = self.index(rows.pop(), column, index)
+            return index
+        def _get_node(self, index: QModelIndex | QPersistentModelIndex):
+            if self._source is None:
+                # The source can briefly be None during widget creation
+                return None  # pragma: no cover
+            # If we have a valid QModelIndex, the internalPointer is the node.
+            # QPersistentModelIndex objects can't store the data, so we need to do a lookup.
+            # The tests don't create persistent model indices, but should handle case anyway
+            # to future-proof for things like drag-and-drop support.
+            if isinstance(index, QModelIndex):
+                if index.isValid():
+                    return index.internalPointer()
+                else:
+                    return self._source
+            else:  # pragma: no cover
+                # build list of row indexes in parents
+                rows = self._get_rows(index)
+                # climb down tree to find node we want
+                node = self._source
+                while rows:
+                    node = node[rows.pop()]
+                return node
+        def _get_rows(self, index: QModelIndex | QPersistentModelIndex):
+            rows = []
+            while index.isValid():
+                rows.append(index.row())
+                index = index.parent()
+            return rows
+        def parent(self, index: QModelIndex) -> QModelIndex:
+            # index should always be valid, but check anyway
+            if index.isValid():  # pragma: no branch
+                node = index.internalPointer()
+                if node._parent is not None:
+                    parent = node._parent
+                    row = parent.index(node)
+                    # We attach the parent node to the index for speed.
+                    # The node must remain alive during the lifetime of the
+                    # QModelIndex() so we cache a reference to it.
+                    self._node_cache[id(parent)] = parent
+                    return self.createIndex(row, 0, parent)
+            return INVALID_INDEX
+        def index(
+            self,
+            row: int,
+            column: int,
+            /,
+            parent: QModelIndex | QPersistentModelIndex = INVALID_INDEX,
+        ) -> QModelIndex:
+            parent_node = self._get_node(parent)
+            if parent_node is None or row >= len(parent_node):
+                # this shouldn't happen in normal operation
+                return INVALID_INDEX  # pragma: no cover
+            else:
+                # We attach the node for the row to the index for speed.
+                # The node must remain alive during the lifetime of the QModelIndex()
+                # so we cache a reference to it.
+                node = parent_node[row]
+                self._node_cache[id(node)] = node
+                return self.createIndex(row, column, node)
+        def rowCount(
+            self,
+            parent: QModelIndex | QPersistentModelIndex = INVALID_INDEX,
+        ) -> int:
+            # this could call out to end-user data sources, so could fail.
+            try:
+                parent_node = self._get_node(parent)
+                if parent_node is None:
+                    # this shouldn't happen in normal operation
+                    return 0  # pragma: no cover
+                else:
+                    return len(parent_node)
+            except Exception:  # pragma: no cover
+                logger.exception("Could not get data length.")
+            return 0  # pragma: no cover
+        def columnCount(
+            self,
+            parent: QModelIndex | QPersistentModelIndex = INVALID_INDEX,
+        ) -> int:
+            # this could call out to end-user data sources, so could fail.
+            try:
+                if self._columns is not None:
+                    return len(self._columns)
+            except Exception:  # pragma: no cover
+                logger.exception("Could not get number of columns.")
+            return 0  # pragma: no cover
+        def data(
+            self,
+            index: QModelIndex | QPersistentModelIndex,
+            /,
+            role: int = Qt.ItemDataRole.DisplayRole,
+        ) -> Any:
+            # Return empty data if index is invalid, shouldn't happen in normal operation
+            # but checking prevents crashes
+            if index.isValid():  # pragma: no branch
+                node = self._get_node(index)
+                column_index = index.column()
+                # this could call out to end-user data sources, so could fail.
+                try:
+                    if self._source is None:
+                        # this can happen briefly during initialization
+                        return None  # pragma: no cover
+                    columns = self._columns
+                    if column_index >= len(columns):
+                        # This should not happen in normal operation, but could occur
+                        # if data changed and notification hasn't been sent
+                        return None  # pragma: no cover
+                    column = columns[column_index]
+                    if column.widget(node) is not None:
+                        warnings.warn(
+                            "Qt does not support the use of widgets in cells",
+                            stacklevel=2,
+                        )
+                    # currently only handle icons and text
+                    if role == Qt.ItemDataRole.DecorationRole:
+                        icon = column.icon(node)
+                        if icon is not None:
+                            return icon._impl.native
+                    elif role == Qt.ItemDataRole.DisplayRole:
+                        return column.text(node, self._missing_value)
+                except Exception:  # pragma: no cover
+                    logger.exception(
+                        f"Could not get data for node {node}, column {column_index}"
+                    )
+            return None
+        def headerData(
+            self,
+            section: int,
+            orientation: Qt.Orientation,
+            /,
+            role: int = Qt.ItemDataRole.DisplayRole,
+        ) -> Any:
+            # QTreeViews only have horizontal headers, but check anyway
+            if orientation == Qt.Orientation.Horizontal:  # pragma: no branch
+                columns = self._columns
+                # this could call out to end-user data sources, so could fail.
+                try:
+                    if section < len(columns):  # pragma: no branch
+                        if role == Qt.ItemDataRole.DisplayRole:
+                            return columns[section].heading
+                except Exception:  # pragma: no cover
+                    logger.exception(f"Could not header for column {section}.")
+            return None
+    class Tree(Widget):
+        def create(self):
+            # Create the List widget
+            self.native = QTreeView()
+            self.native_model = TreeSourceModel(
+                getattr(self.interface, "_data", ListSource(self.interface.accessors)),
+                self.interface._columns[:],
+                self.interface.missing_value,
+                parent=self.native,
+            )
+            self.native.setModel(self.native_model)
+            self.native.setSelectionBehavior(QTreeView.SelectionBehavior.SelectRows)
+            if self.interface.multiple_select:
+                self.native.setSelectionMode(QTreeView.SelectionMode.ExtendedSelection)
+            else:
+                self.native.setSelectionMode(QTreeView.SelectionMode.SingleSelection)
+            if not self.interface._show_headings:
+                # Hide the header
+                self.native.header().hide()
+            self.native.header().setSectionResizeMode(QHeaderView.ResizeMode.Stretch)
+            self.native.selectionModel().selectionChanged.connect(self.qt_selection_changed)
+            self.native.activated.connect(self.qt_activated)
+        def qt_selection_changed(self, added, removed):
+            self.interface.on_select()
+        def qt_activated(self, index):
+            # Invalid index shouldn't occur in normal operation.
+            if index.isValid():  # pragma: no branch
+                self.interface.on_activate(node=self.native_model._get_node(index))
+        def change_source(self, source):
+            self.native_model.set_source(source)
+            self.native.header().resizeSections(QHeaderView.ResizeMode.Stretch)
+        # Listener Protocol implementation
+        def insert(self, index, item, parent=None):
+            self.native_model.insert_item(item=item, index=index, parent=parent)
+        def change(self, item):
+            self.native_model.item_changed(item)
+        def remove(self, index, item, parent=None):
+            self.native_model.remove_item(item=item, index=index, parent=parent)
+        def clear(self):
+            self.native_model.reset_source()
+        def get_selection(self):
+            # Deduplicate selection using row tuples and nodes.
+            indexes = sorted(
+                {
+                    (
+                        tuple(reversed(self.native_model._get_rows(index))),
+                        index.internalPointer(),
+                    )
+                    for index in self.native.selectedIndexes()
+                }
+            )
+            if self.interface.multiple_select:
+                return [node for row, node in indexes]
+            else:
+                return indexes[0][1] if len(indexes) != 0 else None
+        def expand_node(self, item):
+            index = self.native_model._get_index(item)
+            self.native.expandRecursively(index)
+        def expand_all(self):
+            self.native.expandAll()
+        def collapse_node(self, item):
+            index = self.native_model._get_index(item)
+            self.native.collapse(index)
+        def collapse_all(self):
+            self.native.collapseAll()
+        def rehint(self):
+            self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)
+            self.interface.intrinsic.height = at_least(self.interface._MIN_HEIGHT)
+            self.native.header().resizeSections(QHeaderView.ResizeMode.Stretch)
+        def insert_column(self, index, heading, accessor):
+            self.native_model.beginInsertColumns(QModelIndex(), index, index)
+            self.native_model._columns.insert(index, self.interface._columns[index])
+            self.native_model.endInsertColumns()
+            self.native.header().resizeSections(QHeaderView.ResizeMode.Stretch)
+        def remove_column(self, index):
+            self.native_model.beginRemoveColumns(QModelIndex(), index, index)
+            del self.native_model._columns[index]
+            self.native_model.endRemoveColumns()
+            self.native.header().resizeSections(QHeaderView.ResizeMode.Stretch)

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