Ensure Winforms uses DPI scaled sizes.

android/src/toga_android/screens.py

@@ -30,8 +30,9 @@ def get_origin(self):
         return (0, 0)
 
     def get_size(self):
-        return tuple(
-            map(self.scale_out, (self.native.getWidth(), self.native.getHeight()))
+        return (
+            self.scale_out(self.native.getWidth()),
+            self.scale_out(self.native.getHeight()),
         )
 
     def get_image_data(self):

winforms/src/toga_winforms/container.py

@@ -6,7 +6,7 @@
 
 class Container(Scalable):
     def __init__(self, native_parent):
-        self.init_scale(native_parent)
+        super().__init__()
         self.native_parent = native_parent
         self.native_width = self.native_height = 0
         self.content = None

winforms/src/toga_winforms/screens.py

@@ -9,8 +9,10 @@
 
 from toga.screens import Screen as ScreenInterface
 
+from .widgets.base import Scalable
 
-class Screen:
+
+class Screen(Scalable):
     _instances = {}
 
     def __new__(cls, native):
@@ -27,17 +29,24 @@ def get_name(self):
         return self.native.DeviceName
 
     def get_origin(self):
-        return self.native.Bounds.X, self.native.Bounds.Y
+        return (
+            self.scale_out(self.native.Bounds.X),
+            self.scale_out(self.native.Bounds.Y),
+        )
 
     def get_size(self):
-        return self.native.Bounds.Width, self.native.Bounds.Height
+        return (
+            self.scale_out(self.native.Bounds.Width),
+            self.scale_out(self.native.Bounds.Height),
+        )
 
     def get_image_data(self):
-        bitmap = Bitmap(*self.get_size())
+        native_size = self.native.Bounds.Width, self.native.Bounds.Height
+        bitmap = Bitmap(native_size)
         graphics = Graphics.FromImage(bitmap)
-        source_point = Point(*self.get_origin())
+        source_point = Point(self.native.Bounds.X, self.native.Bounds.Y)
         destination_point = Point(0, 0)
-        copy_size = Size(*self.get_size())
+        copy_size = Size(native_size)
         graphics.CopyFromScreen(source_point, destination_point, copy_size)
         stream = MemoryStream()
         bitmap.Save(stream, Imaging.ImageFormat.Png)

winforms/src/toga_winforms/widgets/base.py

@@ -1,8 +1,10 @@
 from abc import ABC, abstractmethod
 from decimal import ROUND_HALF_EVEN, Decimal
 
+from System import IntPtr
 from System.Drawing import (
     Color,
+    Graphics,
     Point,
     Size,
     SystemColors,
@@ -16,8 +18,11 @@
 class Scalable:
     SCALE_DEFAULT_ROUNDING = ROUND_HALF_EVEN
 
-    def init_scale(self, native):
-        self.dpi_scale = native.CreateGraphics().DpiX / 96
+    def __init__(self):
+        super().__init__()
+        self.dpi_scale = (
+            Graphics.FromHdc(Graphics.FromHwnd(IntPtr.Zero).GetHdc()).DpiX / 96
+        )
 
     # Convert CSS pixels to native pixels
     def scale_in(self, value, rounding=SCALE_DEFAULT_ROUNDING):

winforms/src/toga_winforms/window.py

@@ -25,7 +25,6 @@ def __init__(self, interface, title, position, size):
         self.native = WinForms.Form()
         self.native.FormClosing += WeakrefCallable(self.winforms_FormClosing)
         super().__init__(self.native)
-        self.init_scale(self.native)
 
         self.native.MinimizeBox = self.interface.minimizable
         self.native.MaximizeBox = self.interface.resizable