New submission from Terry J. Reedy <tjre...@udel.edu>:
Currently, Shell prints restart lines as
=...= RESTART filename =...=
where filename is 'Shell' or the full pathname. The code is
tag = 'RESTART: ' + (filename if filename else 'Shell')
halfbar = ((int(console.width) -len(tag) - 4) // 2) * '='
console.write("\n{0} {1} {0}".format(halfbar, tag))
The initial '\n' is needed because typically the cursor is sitting at a prompt.
The -4 is from #21192 when I added 'Shell' or filename. It is -2 for the
spaces plus a couple of extra spaces that were there before. I believe -2 is
sufficient but will have to test to be sure.
The number of '='s is the currently the same on both ends. (Because this is
easiest.) It does not have to be, and would sometimes not be if we exactly
filled the console width. I think we should because it would show the actual
non-printable margin and would allow
The minimum number of '='s is 0. The problem revealed in
https://stackoverflow.com/questions/57795679/why-is-this-code-printing-an-empty-line-when-run-under-idle
is that if console.width is exactly 10 + len(filename), the remaining trailing
space wraps to the next line, making it look like a spurious print(' ') had
occurred.
Possible solutions:
0. Do nothing. I rejected this by opening this issue. The SO beginner was
apparently genuinely confused and might not be the only such person. With no
spec for the restart line, this is not an implementation bug but is a design
glitch. As I hinted above, some current details are the result of adding
filenames with minimal change.
1. Delete the ' 's surrounding the tag when there are no '='s. This looks
strange because the '='s visually mark a restart line as much as 'RESTART'.
2. Print a minimum of 1 '=' on each end (by adding them to the format). This
could result in a wrap of exactly ' =' or '=', either of which are bad. If
there is any wrap, it should be the filename, so the user can recognize it as
such.
3. A hybrid solution with a minimum of 1 '=' on the front and 0 on the end,
with no space if no '='. I intend to try this after extracting the restart
line into a testable function and writing tests that now fail.
4. Add a horizontal scrollbar to Shell. This not happening now, might be made
optional, and would still require specification decisions.
----------
assignee: terry.reedy
components: IDLE
messages: 351218
nosy: terry.reedy
priority: normal
severity: normal
stage: test needed
status: open
title: IDLE Shell: Redesign minimum restart line
type: behavior
versions: Python 3.7, Python 3.8, Python 3.9
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue38041>
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