[Qt] Add Selection widget.

Author: windelbouwman

changes/3914.feature.4.md

@@ -0,0 +1 @@
+The Selection widget is now supported in the Qt backend.

docs/en/reference/data/apis_by_platform.yaml

@@ -131,7 +131,6 @@ General widgets:
       - web
     unsupported:
       - textual
-      - qt
 
   Slider:
     description: A widget for selecting a value within a range. The range is shown as a horizontal line, and the selected value is shown as a draggable marker.

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

@@ -16,6 +16,7 @@
     from .widgets.button import Button
     from .widgets.imageview import ImageView
     from .widgets.label import Label
+    from .widgets.selection import Selection
     from .widgets.switch import Switch
     from .widgets.textinput import TextInput
     from .window import MainWindow, Window
@@ -45,6 +46,7 @@
     "Container",
     "Box",
     "Label",
+    "Selection",
     "Switch",
     "TextInput",
     "ImageView",

qt/src/toga_qt/factory.py

@@ -0,0 +1,58 @@
+from contextlib import contextmanager
+
+from PySide6.QtWidgets import QComboBox
+from travertino.size import at_least
+
+from .base import Widget
+
+
+class Selection(Widget):
+    def create(self):
+        self.native = QComboBox()
+        self.native.setSizeAdjustPolicy(QComboBox.SizeAdjustPolicy.AdjustToContents)
+        self.native.currentTextChanged.connect(self.qt_on_current_text_changed)
+        self._send_notifications = True
+
+    @contextmanager
+    def suspend_notifications(self):
+        self._send_notifications = False
+        yield
+        self._send_notifications = True
+
+    def qt_on_current_text_changed(self, text):
+        if self._send_notifications:
+            self.interface.on_change()
+
+    def clear(self):
+        self.native.clear()
+
+    def insert(self, index, item):
+        self.native.insertItem(index, self.interface._title_for_item(item))
+
+    def change(self, item):
+        index = self.interface._items.index(item)
+        with self.suspend_notifications():
+            self.native.setItemText(index, self.interface._title_for_item(item))
+        self.interface.refresh()
+
+    def remove(self, index, item):
+        current_index = self.native.currentIndex()
+        with self.suspend_notifications():
+            self.native.removeItem(index)
+        if index == current_index:
+            if self.native.count() > 0:
+                self.native.setCurrentIndex(0)
+            else:
+                self.interface.on_change()
+
+    def select_item(self, index, item):
+        self.native.setCurrentIndex(index)
+
+    def get_selected_index(self):
+        index = self.native.currentIndex()
+        return None if index == -1 else index
+
+    def rehint(self):
+        content_size = self.native.sizeHint()
+        self.interface.intrinsic.width = at_least(content_size.width())
+        self.interface.intrinsic.height = content_size.height()

qt/src/toga_qt/widgets/selection.py

@@ -0,0 +1,25 @@
+from PySide6.QtWidgets import QComboBox
+
+from .base import SimpleProbe
+
+
+class SelectionProbe(SimpleProbe):
+    native_class = QComboBox
+
+    def assert_resizes_on_content_change(self):
+        pass
+
+    @property
+    def titles(self):
+        titles = [self.native.itemText(index) for index in range(self.native.count())]
+        return titles
+
+    @property
+    def selected_title(self):
+        if self.native.currentIndex() < 0:
+            return None
+        else:
+            return self.native.currentText()
+
+    async def select_item(self):
+        self.native.setCurrentIndex(1)