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#1652 Entry/Leave events cause variable writes
I've report a similiar problem, which was LINUX specific
and eventually blamed on the compiler. This time, it
occurs on multiple platforms.
If a trace is set up to watch writes to a variable, and
the variable is also used as the -variable parameter to a
scale widget, the variable gets written, even though it's
contents remains unchanged, during Leave and Enter
events (NOTE: Depends on value, for example 3.5 is OK,
but 3.4 causes a variable write on all Leave/Enters)
I've attached an example.
Demonstrates Problem
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Confirmed on WinXP with 8.4.5 - 3.5 OK, 3.4 causes write on
enter/leave.
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just a note that similar issues
in the past have come down to
numeric precision issues in
TkRoundToResolution.
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OK, I think we can chalk this one up to TkRoundToResolution,
but what to do about it? You can very easily see why the
problem exists here:
(tk85d) 2 % set tcl_precision 17
17
(tk85d) 3 % expr 3.5-0.1
3.3999999999999999
(tk85d) 4 % expr 3.6-0.1
3.5
So when we internally store "3.4" into the scale value as a
double, it's not /really/ 3.4, so each time we "Round" it,
it is seen as changed.
This affects 8.4.13 and 8.5a4.
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committing attached patch
for 8.4.14 and 8.5a5