Add SupportsIndex support to sequence formatters (#234)

blessed/sequences.py

@@ -273,7 +273,7 @@ def ljust(self, width, fillchar=u' '):
         :rtype: str
         """
         rightside = fillchar * int(
-            (max(0.0, float(width - self.length()))) / float(len(fillchar)))
+            (max(0.0, float(width.__index__() - self.length()))) / float(len(fillchar)))
         return u''.join((self, rightside))
 
     def rjust(self, width, fillchar=u' '):
@@ -287,7 +287,7 @@ def rjust(self, width, fillchar=u' '):
         :rtype: str
         """
         leftside = fillchar * int(
-            (max(0.0, float(width - self.length()))) / float(len(fillchar)))
+            (max(0.0, float(width.__index__() - self.length()))) / float(len(fillchar)))
         return u''.join((leftside, self))
 
     def center(self, width, fillchar=u' '):
@@ -300,7 +300,7 @@ def center(self, width, fillchar=u' '):
         :returns: String of ``text``, centered by ``width``.
         :rtype: str
         """
-        split = max(0.0, float(width) - self.length()) / 2
+        split = max(0.0, float(width.__index__()) - self.length()) / 2
         leftside = fillchar * int(
             (max(0.0, math.floor(split))) / float(len(fillchar)))
         rightside = fillchar * int(
@@ -321,14 +321,15 @@ def truncate(self, width):
         """
         output = ""
         current_width = 0
+        target_width = width.__index__()
         parsed_seq = iter_parse(self._term, self.padd())
 
         # Retain all text until non-cap width reaches desired width
         for text, cap in parsed_seq:
             if not cap:
                 # use wcwidth clipped to 0 because it can sometimes return -1
                 current_width += max(wcwidth(text), 0)
-                if current_width > width:
+                if current_width > target_width:
                     break
             output += text
 

blessed/sequences.pyi

@@ -1,6 +1,6 @@
 # std imports
 import textwrap
-from typing import Any, Type, Tuple, Pattern, TypeVar, Iterator, Optional
+from typing import Any, Type, Tuple, Pattern, TypeVar, Iterator, Optional, SupportsIndex
 
 # local
 from .terminal import Terminal
@@ -38,10 +38,10 @@ class SequenceTextWrapper(textwrap.TextWrapper):
 
 class Sequence(str):
     def __new__(cls: Type[_T], sequence_text: str, term: Terminal) -> _T: ...
-    def ljust(self, width: int, fillchar: str = ...) -> str: ...
-    def rjust(self, width: int, fillchar: str = ...) -> str: ...
-    def center(self, width: int, fillchar: str = ...) -> str: ...
-    def truncate(self, width: int) -> str: ...
+    def ljust(self, width: SupportsIndex, fillchar: str = ...) -> str: ...
+    def rjust(self, width: SupportsIndex, fillchar: str = ...) -> str: ...
+    def center(self, width: SupportsIndex, fillchar: str = ...) -> str: ...
+    def truncate(self, width: SupportsIndex) -> str: ...
     def length(self) -> int: ...
     def strip(self, chars: Optional[str] = ...) -> str: ...
     def lstrip(self, chars: Optional[str] = ...) -> str: ...

tests/test_sequences.py

@@ -728,3 +728,32 @@ def child(kind):
         assert term.truncate(term.red('x' * 1000)) == term.red('x' * term.width)
 
     child(all_terms)
+
+
+def test_supports_index(all_terms):
+    """Ensure sequence formatting methods support objects with __index__()"""
+
+    @as_subprocess
+    def child(kind):
+        from blessed.sequences import Sequence
+        from blessed.terminal import Terminal
+
+        class Indexable:  # pylint: disable=too-few-public-methods
+            """Custom class implementing __index__()"""
+            def __index__(self):
+                return 100
+
+        term = Terminal(kind)
+        seq = Sequence('abcd', term)
+        indexable = Indexable()
+
+        assert seq.rjust(100) == seq.rjust(indexable)
+        assert seq.ljust(100) == seq.ljust(indexable)
+        assert seq.center(100) == seq.center(indexable)
+        assert seq.truncate(100) == seq.truncate(indexable)
+
+        seq = Sequence('abcd' * 30, term)
+        assert seq.truncate(100) == seq.truncate(indexable)
+
+    kind = 'vtwin10' if IS_WINDOWS else 'xterm-256color'
+    child(kind)