background_color Transparency Fixes

android/src/toga_android/widgets/base.py

@@ -1,7 +1,7 @@
 from abc import ABC, abstractmethod
 from decimal import ROUND_HALF_EVEN, Decimal
 
-from android.graphics import PorterDuff, PorterDuffColorFilter, Rect
+from android.graphics import Color, PorterDuff, PorterDuffColorFilter, Rect
 from android.graphics.drawable import ColorDrawable, InsetDrawable
 from android.view import Gravity, View
 from android.widget import RelativeLayout
@@ -138,8 +138,10 @@ def set_background_simple(self, value):
  if not hasattr(self, "_default_background"):
  self._default_background = self.native.getBackground()
 
- if value in (None, TRANSPARENT):
+ if value is None:
  self.native.setBackground(self._default_background)
+ elif value is TRANSPARENT:
+ self.native.setBackgroundColor(Color.TRANSPARENT)
  else:
  background = ColorDrawable(native_color(value))
  if isinstance(self._default_background, InsetDrawable):

android/src/toga_android/widgets/canvas.py

@@ -1,4 +1,5 @@
 import itertools
+import warnings
 from math import degrees
 
 from android.graphics import (
@@ -236,14 +237,20 @@ def _text_paint(self, font):
  paint.setTextSize(self.scale_out(font.size()))
  return paint
 
+ # This has been separated out, so that it can be mocked during testing.
+ def _native_get_background(self):
+ return self.native.getBackground()
+
  def get_image_data(self):
  bitmap = Bitmap.createBitmap(
  self.native.getWidth(), self.native.getHeight(), Bitmap.Config.ARGB_8888
  )
  canvas = A_Canvas(bitmap)
- background = self.native.getBackground()
+ background = self._native_get_background()
  if background:
  background.draw(canvas)
+ else:
+ warnings.warn("Failed to get canvas background")
  self.native.draw(canvas)
 
  stream = ByteArrayOutputStream()

android/src/toga_android/widgets/progressbar.py

@@ -96,3 +96,6 @@ def rehint(self):
  self.interface.intrinsic.height = self.scale_out(
  self.native.getMeasuredHeight(), ROUND_UP
  )
+
+ def set_background_color(self, value):
+ self.set_background_simple(value)

android/tests_backend/widgets/canvas.py

@@ -1,4 +1,5 @@
 from io import BytesIO
+from unittest.mock import Mock
 
 import pytest
 from android.os import SystemClock
@@ -20,6 +21,18 @@ def reference_variant(self, reference):
  def get_image(self):
  return Image.open(BytesIO(self.impl.get_image_data()))
 
+ def test_get_image_data_internal_fail(self, monkeypatch):
+ original_native_get_background = self.impl._native_get_background
+ mock_native_get_background = Mock(return_value=None)
+ monkeypatch.setattr(
+ self.impl, "_native_get_background", mock_native_get_background
+ )
+ with pytest.warns(match="Failed to get canvas background"):
+ self.impl.get_image_data()
+ monkeypatch.setattr(
+ self.impl, "_native_get_background", original_native_get_background
+ )
+
  def motion_event(self, action, x, y):
  time = SystemClock.uptimeMillis()
  super().motion_event(

changes/2484.bugfix.rst

@@ -0,0 +1 @@
+Bugs related to transparent background color are fixed.

cocoa/src/toga_cocoa/widgets/base.py

@@ -75,6 +75,7 @@ def set_color(self, color):
 
  def set_background_color(self, color):
  if color is TRANSPARENT:
+ self.native.backgroundColor = None
  self.native.drawsBackground = False
  else:
  self.native.backgroundColor = native_color(color)

cocoa/src/toga_cocoa/widgets/table.py

@@ -2,6 +2,7 @@
 from travertino.size import at_least
 
 import toga
+from toga.colors import TRANSPARENT
 from toga_cocoa.libs import (
  NSBezelBorder,
  NSIndexSet,
@@ -257,3 +258,9 @@ def remove_column(self, index):
  # delete column and identifier
  self.columns.remove(column)
  self.native_table.sizeToFit()
+
+ def set_background_color(self, color):
+ if color in {None, TRANSPARENT}:
+ super().set_background_color(TRANSPARENT)
+ else:
+ super().set_background_color(color)

cocoa/tests_backend/widgets/canvas.py

@@ -41,6 +41,9 @@ def get_image(self):
  except KeyError:
  return image
 
+ def test_get_image_data_internal_fail(self, monkeypatch):
+ pass
+
  async def mouse_press(self, x, y):
  await self.mouse_event(
  NSEventType.LeftMouseDown,

cocoa/tests_backend/widgets/table.py

@@ -4,7 +4,6 @@
 from toga_cocoa.libs import NSEventType, NSScrollView, NSTableView
 
 from .base import SimpleProbe
-from .properties import toga_color
 
 NSEventModifierFlagCommand = 1 << 20
 
@@ -24,13 +23,6 @@ def __init__(self, widget):
  def font(self):
  skip("Font changes not implemented for Tree on macOS")
 
- @property
- def background_color(self):
- if self.native.drawsBackground:
- return toga_color(self.native.backgroundColor)
- else:
- return None
-
  @property
  def row_count(self):
  return int(self.native_table.numberOfRowsInTableView(self.native_table))

gtk/tests_backend/widgets/canvas.py

@@ -19,6 +19,9 @@ def reference_variant(self, reference):
  def get_image(self):
  return Image.open(BytesIO(self.impl.get_image_data()))
 
+ def test_get_image_data_internal_fail(self, monkeypatch):
+ pass
+
  async def mouse_press(self, x, y):
  event = Gdk.Event.new(Gdk.EventType.BUTTON_PRESS)
  event.button = 1

iOS/src/toga_iOS/widgets/progressbar.py

@@ -105,6 +105,9 @@ def set_max(self, value):
  self._max = value
  self._stop_indeterminate()
 
+ def set_background_color(self, color):
+ self.set_background_color_simple(color)
+
  def rehint(self):
  fitting_size = self.native.systemLayoutSizeFittingSize(CGSize(0, 0))
  self.interface.intrinsic.width = at_least(self.interface._MIN_WIDTH)

iOS/tests_backend/widgets/canvas.py

@@ -33,6 +33,9 @@ def reference_variant(self, reference):
  def get_image(self):
  return Image.open(BytesIO(self.impl.get_image_data()))
 
+ def test_get_image_data_internal_fail(self, monkeypatch):
+ pass
+
  async def mouse_press(self, x, y):
  touch = MockTouch.alloc().init()
  touches = NSSet.setWithObject(touch)

testbed/tests/widgets/properties.py

@@ -393,14 +393,12 @@ async def test_background_color_reset(widget, probe):
 
  # Set the background color to something different
  widget.style.background_color = RED
- await probe.redraw("Widget background background color should be RED")
+ await probe.redraw("Widget background color should be RED")
  assert_color(probe.background_color, named_color(RED))
 
  # Reset the background color, and check that it has been restored to the original
  del widget.style.background_color
- await probe.redraw(
- message="Widget background background color should be restored to original"
- )
+ await probe.redraw(message="Widget background color should be restored to original")
  assert_color(probe.background_color, original)
 
 
@@ -409,10 +407,21 @@ async def test_background_color_transparent(widget, probe):
  original = probe.background_color
  supports_alpha = getattr(probe, "background_supports_alpha", True)
 
+ # Set the background color to something different
+ widget.style.background_color = RED
+ await probe.redraw("Widget background color should be RED")
+ assert_color(probe.background_color, named_color(RED))
+
+ # Change the background color to transparent
  widget.style.background_color = TRANSPARENT
- await probe.redraw("Widget background background color should be TRANSPARENT")
+ await probe.redraw("Widget background color should be TRANSPARENT")
  assert_color(probe.background_color, TRANSPARENT if supports_alpha else original)
 
+ # Restore original background color
+ del widget.style.background_color
+ await probe.redraw("Widget background color should be restored to original")
+ assert_color(probe.background_color, original)
+
 
 async def test_alignment(widget, probe, verify_vertical_alignment):
  """Widget honors alignment settings."""

testbed/tests/widgets/test_box.py

@@ -6,6 +6,7 @@
 from .properties import ( # noqa: F401
  test_background_color,
  test_background_color_reset,
+ test_background_color_transparent,
  test_enable_noop,
  test_flex_widget_size,
  test_focus_noop,

testbed/tests/widgets/test_canvas.py

@@ -212,7 +212,7 @@ async def test_alt_drag(
  on_alt_release_handler.assert_called_once_with(canvas, 70, 90)
 
 
-async def test_image_data(canvas, probe):
+async def test_image_data(monkeypatch, canvas, probe):
  "The canvas can be saved as an image"
  with canvas.Stroke(x=0, y=0, color=RED) as stroke:
  stroke.line_to(x=200, y=200)
@@ -237,6 +237,10 @@ async def test_image_data(canvas, probe):
  screen=canvas.window.screen,
  )
 
+ # The internal method to patch for testing are platform specific
+ # hence the test is on the probe.
+ probe.test_get_image_data_internal_fail(monkeypatch)
+
 
 def assert_reference(probe, reference, threshold=0.0):
  """Assert that the canvas currently matches a reference image, within an RMS threshold"""

testbed/tests/widgets/test_divider.py

@@ -6,6 +6,9 @@
 
 from ..conftest import skip_on_platforms
 from .properties import ( # noqa: F401
+ test_background_color,
+ test_background_color_reset,
+ test_background_color_transparent,
  test_enable_noop,
  test_focus_noop,
 )

testbed/tests/widgets/test_progressbar.py

@@ -3,6 +3,9 @@
 import toga
 
 from .properties import ( # noqa: F401
+ test_background_color,
+ test_background_color_reset,
+ test_background_color_transparent,
  test_enable_noop,
  test_flex_horizontal_widget_size,
 )

testbed/tests/widgets/test_table.py

@@ -12,6 +12,7 @@
 from .properties import ( # noqa: F401
  test_background_color,
  test_background_color_reset,
+ test_background_color_transparent,
  test_enable_noop,
  test_flex_widget_size,
  test_focus_noop,

winforms/src/toga_winforms/widgets/progressbar.py

@@ -20,6 +20,8 @@
 
 
 class ProgressBar(Widget):
+ _background_supports_alpha = False
+
  TOGA_SCALE = 1000
 
  def create(self):

winforms/tests_backend/widgets/canvas.py

@@ -17,6 +17,9 @@ def reference_variant(self, reference):
  def get_image(self):
  return Image.open(BytesIO(self.impl.get_image_data()))
 
+ def test_get_image_data_internal_fail(self, monkeypatch):
+ pass
+
  async def mouse_press(self, x, y, **kwargs):
  self.native.OnMouseDown(self.mouse_event(x, y, **kwargs))
  self.native.OnMouseUp(self.mouse_event(x, y, **kwargs))

winforms/tests_backend/widgets/progressbar.py

@@ -5,6 +5,7 @@
 
 class ProgressBarProbe(SimpleProbe):
  native_class = System.Windows.Forms.ProgressBar
+ background_supports_alpha = False
 
  @property
  def is_determinate(self):