Fix `TextCanvas` `CanvasError("Attribute extends beyond text...")` (#555)HEADmaster

* Fix TextCanvas `CanvasError("Attribute extends beyond text...")

* `[[]] * ...` causes
  list of 1 list with pointers
  amount equal to multiplier
  instead of "list of lists"
* Add 2 basic font tests which check for Canvas create issue
* Add few type annotations during debug process

Fix: #554

* Force tests to restore default encoding in tearDown

Tests order change should not cause tests failures

---------

Co-authored-by: Aleksei Stepanov <alekseis@nvidia.com>

8 files changed, 172 insertions, 40 deletions

diff --git a/urwid/canvas.py b/urwid/canvas.py
index ed71c54..4d467e8 100644
--- a/urwid/canvas.py
+++ b/urwid/canvas.py
@@ -61,7 +61,7 @@ class CanvasCache:
     """
     _widgets = {}
     _refs = {}
-    _deps = {}
+    _deps: dict[Widget, list[Widget]] = {}
     hits = 0
     fetches = 0
     cleanups = 0
@@ -157,7 +157,7 @@ class CanvasCache:
 
     @classmethod
     def cleanup(cls, ref):
-        cls.cleanups += 1 # collect stats
+        cls.cleanups += 1  # collect stats
 
         w = cls._refs.get(ref, None)
         del cls._refs[ref]
@@ -198,12 +198,16 @@ class Canvas:
     """
     cacheable = True
 
-    _finalized_error = CanvasError("This canvas has been finalized. "
+    _finalized_error = CanvasError(
+        "This canvas has been finalized. "
         "Use CompositeCanvas to wrap this canvas if "
-        "you need to make changes.")
-    _renamed_error = CanvasError("The old Canvas class is now called "
+        "you need to make changes."
+    )
+    _renamed_error = CanvasError(
+        "The old Canvas class is now called "
         "TextCanvas. Canvas is now the base class for all canvas "
-        "classes.")
+        "classes."
+    )
 
     def __init__(
         self,
@@ -221,7 +225,12 @@ class Canvas:
         self.coords = {}
         self.shortcuts = {}
 
-    def finalize(self, widget, size, focus):
+    def finalize(
+        self,
+        widget: Widget,
+        size: tuple[()] | tuple[int] | tuple[int, int],
+        focus: bool,
+    ) -> None:
         """
         Mark this canvas as finalized (should not be any future
         changes to its content). This is required before caching
@@ -386,9 +395,9 @@ class TextCanvas(Canvas):
                 maxcol = 0
 
         if attr is None:
-            attr = [[]] * len(text)
+            attr = [[] for _ in range(len(text))]
         if cs is None:
-            cs = [[]] * len(text)
+            cs = [[] for _ in range(len(text))]
 
         # pad text and attr to maxcol
         for i in range(len(text)):
@@ -397,11 +406,11 @@ class TextCanvas(Canvas):
                 raise CanvasError(f"Canvas text is wider than the maxcol specified \n{maxcol!r}\n{widths!r}\n{text!r}")
             if w < maxcol:
                 text[i] += b''.rjust(maxcol - w)
-            a_gap = len(text[i]) - rle_len( attr[i] )
+            a_gap = len(text[i]) - rle_len(attr[i])
             if a_gap < 0:
-                raise CanvasError(f"Attribute extends beyond text \n{text[i]!r}\n{attr[i]!r}" )
+                raise CanvasError(f"Attribute extends beyond text \n{text[i]!r}\n{attr[i]!r}")
             if a_gap:
-                rle_append_modify( attr[i], (None, a_gap))
+                rle_append_modify(attr[i], (None, a_gap))
 
             cs_gap = len(text[i]) - rle_len( cs[i] )
             if cs_gap < 0:
diff --git a/urwid/curses_display.py b/urwid/curses_display.py
index e9519f7..86805f8 100755
--- a/urwid/curses_display.py
+++ b/urwid/curses_display.py
@@ -597,10 +597,10 @@ class _test:
         attr += [[],[],[]]
         cols,rows = self.ui.get_cols_rows()
         keys = None
-        while keys!=['q']:
-            r.text=([t.ljust(cols) for t in text]+[""]*rows)[:rows]
-            r.attr=(attr+[[]]*rows) [:rows]
-            self.ui.draw_screen((cols,rows),r)
+        while keys != ['q']:
+            r.text = ([t.ljust(cols) for t in text] + [""] * rows)[:rows]
+            r.attr = (attr + [[] for _ in range(rows)])[:rows]
+            self.ui.draw_screen((cols, rows), r)
             keys, raw = self.ui.get_input( raw_keys = True )
             if 'window resize' in keys:
                 cols, rows = self.ui.get_cols_rows()
diff --git a/urwid/tests/test_canvas.py b/urwid/tests/test_canvas.py
index 5a1d454..d0c624c 100644
--- a/urwid/tests/test_canvas.py
+++ b/urwid/tests/test_canvas.py
@@ -302,6 +302,12 @@ class CanvasJoinTest(unittest.TestCase):
 
 
 class CanvasOverlayTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def cotest(self, desc, bgt, bga, fgt, fga, l, r, et):
         bgt = bgt.encode('iso8859-1')
         fgt = fgt.encode('iso8859-1')
diff --git a/urwid/tests/test_font.py b/urwid/tests/test_font.py
new file mode 100644
index 0000000..3c9be7a
--- /dev/null
+++ b/urwid/tests/test_font.py
@@ -0,0 +1,30 @@
+from __future__ import annotations
+
+import unittest
+
+import urwid
+
+
+class TestFontRender(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
+    def test_001_basic(self):
+        font = urwid.Thin3x3Font()
+        rendered = b'\n'.join(font.render("1").text).decode()
+        expected = ' ┐ \n │ \n ┴ '
+        self.assertEqual(expected, rendered)
+
+    def test_002_non_rect(self):
+        """Test non rect symbol, which causes spaces based padding.
+
+        Lines as bytes should be not equal length.
+        """
+        font = urwid.Thin3x3Font()
+        rendered = b'\n'.join(font.render("2").text).decode()
+        expected = '┌─┐\n┌─┘\n└─ '
+        self.assertEqual(expected, rendered)
diff --git a/urwid/tests/test_graphics.py b/urwid/tests/test_graphics.py
index f731208..1ae1f98 100644
--- a/urwid/tests/test_graphics.py
+++ b/urwid/tests/test_graphics.py
@@ -7,6 +7,13 @@ from urwid import graphics
 
 
 class LineBoxTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def border(self, tl, t, tr, l, r, bl, b, br):
         return [b''.join([tl, t, tr]),
                 b''.join([l, b" ", r]),
@@ -14,7 +21,6 @@ class LineBoxTest(unittest.TestCase):
 
     def test_linebox_pack(self):
         # Bug #346 'pack' Padding does not run with LineBox
-        urwid.set_encoding("utf-8")
         t = urwid.Text("AAA\nCCC\nDDD")
         size = t.pack()
         l = urwid.LineBox(t)
@@ -23,7 +29,6 @@ class LineBoxTest(unittest.TestCase):
         self.assertEqual(l.pack()[1], size[1] + 2)
 
     def test_linebox_border(self):
-        urwid.set_encoding("utf-8")
         t = urwid.Text("")
 
         l = urwid.LineBox(t).render((3,)).text
@@ -87,8 +92,14 @@ class BarGraphTest(unittest.TestCase):
              (1,[(3,3)]) ] )
 
 class SmoothBarGraphTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+        urwid.set_encoding("utf-8")
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def sbgtest(self, desc, data, top, exp ):
-        urwid.set_encoding('utf-8')
         g = urwid.BarGraph( ['black','red','blue'],
                 None, {(1,0):'red/black', (2,1):'blue/red'})
         g.set_data( data, top )
diff --git a/urwid/tests/test_text_layout.py b/urwid/tests/test_text_layout.py
index c87d12c..95cba1c 100644
--- a/urwid/tests/test_text_layout.py
+++ b/urwid/tests/test_text_layout.py
@@ -1,11 +1,24 @@
 from __future__ import annotations
 
+import contextlib
 import unittest
+from collections.abc import Generator
 
 import urwid
 from urwid import text_layout
 
 
+@contextlib.contextmanager
+def encoding(encoding_name: str) -> Generator[None, None, None]:
+    old_encoding = 'ascii'  # Default fallback value
+    try:
+        old_encoding = urwid.util._target_encoding
+        urwid.set_encoding(encoding_name)
+        yield
+    finally:
+        urwid.set_encoding(old_encoding)
+
+
 class CalcBreaksTest:
     def cbtest(self, width, exp):
         result = text_layout.default_layout.calculate_text_segments(
@@ -33,8 +46,12 @@ class CalcBreaksCharTest(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksDBCharTest(CalcBreaksTest, unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'any'
     text = "abfgh\xA1\xA1j\xA1\xA1xskhtrvs\naltjhgsdf\xA1\xA1jahtshgf"
     # tests
@@ -68,8 +85,12 @@ class CalcBreaksWordTest2(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksDBWordTest(CalcBreaksTest, unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'space'
     text = "hel\xA1\xA1 world\nout-\xA1\xA1tre blah"
     # tests
@@ -81,9 +102,13 @@ class CalcBreaksDBWordTest(CalcBreaksTest, unittest.TestCase):
 
 
 class CalcBreaksUTF8Test(CalcBreaksTest, unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("utf-8")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     mode = 'space'
     text = '\xe6\x9b\xbf\xe6\xb4\xbc\xe6\xb8\x8e\xe6\xba\x8f\xe6\xbd\xba'
     do = [
@@ -95,20 +120,28 @@ class CalcBreaksUTF8Test(CalcBreaksTest, unittest.TestCase):
 
 class CalcBreaksCantDisplayTest(unittest.TestCase):
     def test(self):
-        urwid.set_encoding("euc-jp")
-        self.assertRaises(text_layout.CanNotDisplayText,
-            text_layout.default_layout.calculate_text_segments,
-            b'\xA1\xA1', 1, 'space' )
-        urwid.set_encoding("utf-8")
-        self.assertRaises(text_layout.CanNotDisplayText,
-            text_layout.default_layout.calculate_text_segments,
-            b'\xe9\xa2\x96', 1, 'space' )
+        with encoding("euc-jp"):
+            self.assertRaises(
+                text_layout.CanNotDisplayText,
+                text_layout.default_layout.calculate_text_segments,
+                b'\xA1\xA1', 1, 'space'
+            )
+        with encoding("utf-8"):
+            self.assertRaises(
+                text_layout.CanNotDisplayText,
+                text_layout.default_layout.calculate_text_segments,
+                b'\xe9\xa2\x96', 1, 'space'
+            )
 
 
 class SubsegTest(unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def st(self, seg, text, start, end, exp):
         text = text.encode('iso8859-1')
         s = urwid.LayoutSegment(seg)
@@ -151,9 +184,13 @@ class SubsegTest(unittest.TestCase):
 
 
 class CalcTranslateTest:
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("utf-8")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def test1_left(self):
         result = urwid.default_layout.layout( self.text,
             self.width, 'left', self.mode)
@@ -225,9 +262,13 @@ class CalcTranslateWordTest2(CalcTranslateTest, unittest.TestCase):
 
 
 class CalcTranslateWordTest3(CalcTranslateTest, unittest.TestCase):
-    def setUp(self):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding('utf-8')
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     text = b'\xe6\x9b\xbf\xe6\xb4\xbc\n\xe6\xb8\x8e\xe6\xba\x8f\xe6\xbd\xba'
     width = 10
     mode = 'space'
diff --git a/urwid/tests/test_util.py b/urwid/tests/test_util.py
index 06de8c8..d893eac 100644
--- a/urwid/tests/test_util.py
+++ b/urwid/tests/test_util.py
@@ -8,6 +8,12 @@ from urwid import util
 
 
 class CalcWidthTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def wtest(self, desc, s, exp):
         s = s.encode('iso8859-1')
         result = util.calc_width( s, 0, len(s))
@@ -29,6 +35,12 @@ class CalcWidthTest(unittest.TestCase):
 
 
 class ConvertDecSpecialTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def ctest(self, desc, s, exp, expcs):
         exp = exp.encode('iso8859-1')
         util.set_encoding('ascii')
@@ -51,8 +63,12 @@ class ConvertDecSpecialTest(unittest.TestCase):
 
 class WithinDoubleByteTest(unittest.TestCase):
     def setUp(self):
+        self.old_encoding = urwid.util._target_encoding
         urwid.set_encoding("euc-jp")
 
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def wtest(self, s, ls, pos, expected, desc):
         result = util.within_double_byte(s.encode('iso8859-1'), ls, pos)
         assert result==expected, f"{desc} got:{result!r} expected: {expected!r}"
@@ -88,6 +104,12 @@ class WithinDoubleByteTest(unittest.TestCase):
 
 
 class CalcTextPosTest(unittest.TestCase):
+    def setUp(self) -> None:
+        self.old_encoding = urwid.util._target_encoding
+
+    def tearDown(self) -> None:
+        urwid.set_encoding(self.old_encoding)
+
     def ctptest(self, text, tests):
         text = text.encode('iso8859-1')
         for s,e,p, expected in tests:
diff --git a/urwid/tests/test_widget.py b/urwid/tests/test_widget.py
index 4ea2944..9da2abb 100644
--- a/urwid/tests/test_widget.py
+++ b/urwid/tests/test_widget.py
@@ -1,10 +1,23 @@
 from __future__ import annotations
 
+import contextlib
 import unittest
+from collections.abc import Generator
 
 import urwid
 
 
+@contextlib.contextmanager
+def encoding(encoding_name: str) -> Generator[None, None, None]:
+    old_encoding = 'ascii'  # Default fallback value
+    try:
+        old_encoding = urwid.util._target_encoding
+        urwid.set_encoding(encoding_name)
+        yield
+    finally:
+        urwid.set_encoding(old_encoding)
+
+
 class TextTest(unittest.TestCase):
     def setUp(self):
         self.t = urwid.Text("I walk the\ncity in the night")
@@ -33,10 +46,10 @@ class TextTest(unittest.TestCase):
         assert got == expected, f"got: {got!r} expected: {expected!r}"
 
     def test5_encode_error(self):
-        urwid.set_encoding("ascii")
-        expected = [b"?  "]
-        got = urwid.Text('û').render((3,))._text
-        assert got == expected, f"got: {got!r} expected: {expected!r}"
+        with encoding("ascii"):
+            expected = [b"?  "]
+            got = urwid.Text('û').render((3,))._text
+            assert got == expected, f"got: {got!r} expected: {expected!r}"
 
 
 class EditTest(unittest.TestCase):
@@ -87,12 +100,12 @@ class EditTest(unittest.TestCase):
         self.ktest(self.t3,'down','down',15,"down at bottom")
 
     def test_utf8_input(self):
-        urwid.set_encoding("utf-8")
-        self.t1.set_edit_text('')
-        self.t1.keypress((12,), 'û')
-        self.assertEqual(self.t1.edit_text, 'û'.encode())
-        self.t4.keypress((12,), 'û')
-        self.assertEqual(self.t4.edit_text, 'û')
+        with encoding("utf-8"):
+            self.t1.set_edit_text('')
+            self.t1.keypress((12,), 'û')
+            self.assertEqual(self.t1.edit_text, 'û'.encode())
+            self.t4.keypress((12,), 'û')
+            self.assertEqual(self.t4.edit_text, 'û')
 
 
 class EditRenderTest(unittest.TestCase):