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serhiy-storchakaclaude
serhiy-storchaka
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claude
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gh-90304: Fix IDLE startup failure with a broken font (#152419)
On some systems a font reports a zero width for the '0' character (seen with a broken font on openSUSE). EditorWindow.set_width() divides the Text widget's pixel width by that value, so the ZeroDivisionError prevented IDLE from starting at all. set_width() now falls back to the configured width when the measured width is zero. self.width is consumed by the === RESTART === separator in the shell and by the squeezer's line wrapping. Co-authored-by: Claude Opus 4.8 <[email protected]>
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Lines changed: 20 additions & 1 deletion

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‎Lib/idlelib/editor.py‎

Lines changed: 3 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -325,7 +325,9 @@ def set_width(self):
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# http://www.tcl.tk/man/tcl8.6/TkCmd/text.htm#M21
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zero_char_width = \
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Font(text, font=text.cget('font')).measure('0')
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self.width = pixel_width // zero_char_width
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# Some fonts report a zero width for '0' (gh-90304).
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self.width = (pixel_width // zero_char_width if zero_char_width
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else text.tk.getint(text.cget('width')))
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def new_callback(self, event):
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dirname, basename = self.io.defaultfilename()

‎Lib/idlelib/idle_test/test_editor.py‎

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Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
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from idlelib import editor
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import unittest
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from collections import namedtuple
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from unittest import mock
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from test.support import requires
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from tkinter import Tk, Text
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@@ -30,6 +31,18 @@ def test_init(self):
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self.assertEqual(e.root, self.root)
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e._close()
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def test_set_width_zero_char_width(self):
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# A zero-width '0' must not raise ZeroDivisionError (gh-90304).
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e = Editor(root=self.root)
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try:
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with mock.patch.object(editor, 'Font') as MockFont:
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MockFont.return_value.measure.return_value = 0
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e.set_width()
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self.assertEqual(e.width,
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e.text.tk.getint(e.text.cget('width')))
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finally:
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e._close()
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class GetLineIndentTest(unittest.TestCase):
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def test_empty_lines(self):

‎Misc/NEWS.d/next/IDLE/2026-06-27-17-27-21.gh-issue-90304.464d22.rst‎

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@@ -0,0 +1,4 @@
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Prevent IDLE from failing to start when a font reports a zero width for
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the ``'0'`` character. Such a broken font caused a
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:exc:`ZeroDivisionError`; the editor now falls back to the configured
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width.

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