Fix render regression: khal Padding widh > size

Allow to render `Padding` with GIVEN width > size.
Warn about incorrect size

Fix: pimutils/khal#1334

tests/test_padding.py

@@ -161,6 +161,14 @@ def test_fixed(self) -> None:
         widget.keypress((), "right")
         self.assertEqual("Cancel", body.focus.focus.label)
 
+    def test_insufficient_space(self):
+        width = 10
+        widget = urwid.Padding(urwid.Text("Some text"), width=width)
+        with self.assertWarns(urwid.widget.PaddingWarning) as ctx:
+            canvas = widget.render((width - 1,))
+        self.assertEqual("Some text", str(canvas))
+        self.assertEqual(width - 1, canvas.cols())
+
     def ptest(self, desc, align, width, maxcol, left, right, min_width=None):
         p = urwid.Padding(None, align, width, min_width)
         l, r = p.padding_values((maxcol,), False)

urwid/widget/padding.py

@@ -316,10 +316,17 @@ def render(
 
         if self._width_type == WHSettings.CLIP:
             canv = self._original_widget.render((), focus)
+        elif size:
+            maxcol = size[0] - (left + right)
+            if self._width_type == WHSettings.GIVEN and maxcol < self._width_amount:
+                warnings.warn(
+                    f"{self}.render(size={size}, focus={focus}): too narrow size ({maxcol!r} < {self._width_amount!r})",
+                    PaddingWarning,
+                    stacklevel=3,
+                )
+            canv = self._original_widget.render((maxcol,) + size[1:], focus)
         elif self._width_type == WHSettings.GIVEN:
             canv = self._original_widget.render((self._width_amount,) + size[1:], focus)
-        elif size:
-            canv = self._original_widget.render((size[0] - (left + right),) + size[1:], focus)
         else:
             canv = self._original_widget.render((), focus)