Setting the font of a toga.Selection (Android and Winforms)

examples/selection/selection/app.py

@@ -8,6 +8,7 @@ class SelectionApp(toga.App):
     YTTERBIUM = "Ytterbium"
     THULIUM = "Thulium"
     OPTIONS = [CARBON, YTTERBIUM, THULIUM]
+    lbl_fontsize = None
 
     def startup(self):
         # Main window of the application with title and size
@@ -17,11 +18,36 @@ def startup(self):
         label_style = Pack(flex=1, padding_right=24)
         box_style = Pack(direction=ROW, padding=10)
 
+        # Change font size
+        lbl_fontlabel = toga.Label("Font size =")
+        self.lbl_fontsize = toga.Label("14")
+        btn_reduce_size = toga.Button(
+            " - ", on_press=self.reduce_fontsize, style=Pack(width=40)
+        )
+        btn_increase_size = toga.Button(
+            " + ", on_press=self.increase_fontsize, style=Pack(width=40)
+        )
+        font_box = toga.Box(
+            children=[
+                lbl_fontlabel,
+                self.lbl_fontsize,
+                btn_reduce_size,
+                btn_increase_size,
+            ],
+            style=box_style,
+        )
+
         # Add the content on the main window
-        self.selection = toga.Selection(items=self.OPTIONS)
+        self.selection = toga.Selection(
+            items=self.OPTIONS,
+            style=Pack(
+                font_family="monospace", font_size=int(self.lbl_fontsize.text), font_style="italic"
+            )
+        )
 
         self.main_window.content = toga.Box(
             children=[
+                font_box,
                 toga.Box(
                     style=box_style,
                     children=[
@@ -114,6 +140,18 @@ def my_on_select(self, selection):
 
         print("The selection widget changed to {0}".format(selection.value))
 
+    def reduce_fontsize(self, widget):
+        font_size = int(self.lbl_fontsize.text) - 1
+        self.lbl_fontsize.text = str(font_size)
+        font = toga.Font("monospace", font_size, style="italic")
+        self.selection._impl.set_font(font)
+
+    def increase_fontsize(self, widget):
+        font_size = int(self.lbl_fontsize.text) + 1
+        self.lbl_fontsize.text = str(font_size)
+        font = toga.Font("monospace", font_size, style="italic")
+        self.selection._impl.set_font(font)
+
 
 def main():
     # App name and namespace

src/android/toga_android/widgets/selection.py

@@ -1,10 +1,14 @@
+from rubicon.java import JavaClass
 from travertino.size import at_least
 
 from ..libs.android import R__layout
+from ..libs.android.util import TypedValue
 from ..libs.android.view import Gravity, View__MeasureSpec
-from ..libs.android.widget import ArrayAdapter, OnItemSelectedListener, Spinner
+from ..libs.android.widget import OnItemSelectedListener, Spinner
 from .base import Widget, align
 
+BeewareSpinnerAdapter = JavaClass("org/beeware/android/BeewareSpinnerAdapter")
+
 
 class TogaOnItemSelectedListener(OnItemSelectedListener):
     def __init__(self, impl):
@@ -23,13 +27,9 @@ def create(self):
             impl=self
         ))
         # On Android, the list of options is provided to the `Spinner` wrapped in
-        # an `ArrayAdapter`. We store `self.adapter` to avoid having to typecast it
-        # in `add_item()`.
-        self.adapter = ArrayAdapter(
-            self._native_activity,
-            R__layout.simple_spinner_item
-        )
-        self.adapter.setDropDownViewResource(R__layout.simple_spinner_dropdown_item)
+        # a `BeewareSpinnerAdapter`. We store `self.adapter` to avoid
+        # having to typecast it in `add_item()`.
+        self.adapter = BeewareSpinnerAdapter(self._native_activity, R__layout.simple_spinner_item)
         self.native.setAdapter(self.adapter)
         # Create a mapping from text to numeric index to support `select_item()`.
         self._indexByItem = {}
@@ -61,3 +61,10 @@ def set_alignment(self, value):
     def set_on_select(self, handler):
         # No special handling is required.
         pass
+
+    def set_font(self, font):
+        if font:
+            font_impl = font.bind(self.interface.factory)
+            self.adapter.setSpinnerTextSize(TypedValue.COMPLEX_UNIT_SP, int(font_impl.get_size()))
+            self.adapter.setSpinnerTypeFace(font_impl.get_typeface(), font_impl.get_style())
+            self.adapter.notifyDataSetChanged()

src/winforms/toga_winforms/widgets/selection.py

@@ -40,6 +40,10 @@ def get_selected_item(self):
     def set_on_select(self, handler):
         pass
 
+    def set_font(self, font):
+        if font:
+            self.native.Font = font.bind(self.interface.factory).native
+
     def rehint(self):
         self.interface.intrinsic.width = at_least(self.native.PreferredSize.Width)
         self.interface.intrinsic.height = self.native.PreferredSize.Height