Remove use of shadow attribute for button label.

android/src/toga_android/widgets/button.py

@@ -24,6 +24,9 @@ def create(self):
         self.native = A_Button(self._native_activity)
         self.native.setOnClickListener(TogaOnClickListener(button_impl=self))
 
+    def get_text(self):
+        return str(self.native.getText())
+
     def set_text(self, text):
         self.native.setText(self.interface.text)
 

cocoa/src/toga_cocoa/widgets/button.py

@@ -66,8 +66,11 @@ def set_font(self, font):
         # Button style is sensitive to font changes
         self._set_button_style()
 
+    def get_text(self):
+        return str(self.native.title)
+
     def set_text(self, text):
-        self.native.title = self.interface.text
+        self.native.title = text
 
     def set_on_press(self, handler):
         # No special handling required

core/src/toga/widgets/button.py

@@ -89,14 +89,14 @@ def __init__(
     @property
     def text(self):
         """The text displayed on the button."""
-        return self._text
+        return self._impl.get_text()
 
     @text.setter
     def text(self, value):
         if value is None:
-            self._text = ""
+            value = ""
         else:
-            self._text = str(value)
+            value = str(value)
         self._impl.set_text(value)
         self._impl.rehint()
 

dummy/src/toga_dummy/widgets/button.py

@@ -6,7 +6,10 @@ def create(self):
         self._action("create Button")
 
     def set_text(self, text):
-        self._set_value("text", self.interface.text)
+        self._set_value("text", text)
+
+    def get_text(self):
+        return self._get_value("text")
 
     def set_on_press(self, handler):
         self._set_value("on_press", handler)

gtk/src/toga_gtk/widgets/button.py

@@ -12,6 +12,9 @@ def create(self):
         self.native.connect("show", lambda event: self.rehint())
         self.native.connect("clicked", self.gtk_on_press)
 
+    def get_text(self):
+        return self.native.get_label()
+
     def set_text(self, text):
         self.native.set_label(self.interface.text)
         self.rehint()

iOS/src/toga_iOS/widgets/button.py

@@ -38,6 +38,9 @@ def create(self):
         # Add the layout constraints
         self.add_constraints()
 
+    def get_text(self):
+        return str(self.native.title)
+
     def set_text(self, text):
         self.native.setTitle(self.interface.text, forState=UIControlStateNormal)
 

web/src/toga_web/widgets/button.py

@@ -13,6 +13,9 @@ def dom_onclick(self, event):
         if self.interface.on_press:
             self.interface.on_press(self.interface)
 
+    def get_text(self):
+        return self.native.innerHTML
+
     def set_text(self, text):
         self.native.innerHTML = text
 

winforms/src/toga_winforms/widgets/button.py

@@ -18,6 +18,9 @@ def winforms_click(self, sender, event):
             if self.interface.on_press:
                 self.interface.on_press(self.interface)
 
+    def get_text(self):
+        return self.native.Text
+
     def set_text(self, text):
         self.native.Text = self.interface.text
         self.rehint()