[Libreoffice-ux-advise] Chart: what to do when trendline (regression) equation is too long tdf#94004

Hello,

If your trendline equation is too long (for instance with a high degree
polynomial trendline) then :
- end of equation is not visible [1]
- chart is squeezed when exiting chart [2]
See bug 94004 [3]
To fix this bug there could be (at least) two ways:
(a) if General format is used for equation, number of decimal digits should
be adapted to fit equation in chart width
(b) we should alert user that equation is too long and let him make a
decision: change number format, change font size, increase chart width

I proposed a commit [4] for solution (a), but Moggi have some concerns about
it and would prefer solution (b).

moggi wrote
> I'm not sure if that is really a good approach. In general I think instead
> of trying to change the equation we should make it clear to the user that
> we could not layout his chart correctly and that he should look into
> fixing the layout. So a more make the user aware of the problems than
> trying to work around problems.
> I suggest that you contact the UX team and tell them about your idea and
> my concerns.
> [...]
> If they have more questions they can contact me.

IMHO, if General number format is used, it should automatically adapt its
length to chart width like it does in a cell with column width. With General
format, user does not bother about specific notation (normal or scientific)
nor precision (as many as digits as it could). For instance, if intercept is
forced to 1 (you can set its value through trendline dialog), there is no
need for a large number of significant digits for intercept value; but other
values of polynomial equation may display much more digits. Only General
format can deal with different precision for each value of polynomial
equation. So user could not fix the problem by means of a specific number
format: all values of polynomial equation will have the same format.

However, solution (a) does not fix the bug if user chose a specific number
format that creates a too long equation. In this case, user is already aware
of the problem when chart is opened (as it can be seen on screenshot [1]).
And when chart is closed, I propose that trendline equation should be cut to
chart width and ended with a red triangle (like when text length exceeds
column width within a cell). So that chart is not shrink like in screenshot
[2], and "make the user aware of the problems" with solution (b).

So now we are expecting your advices about these two solutions.

Many thanks in advance for your comments.

Best regards,

Laurent BP

[1] https://bugs.documentfoundation.org/attachment.cgi?id=121807
[2] https://bugs.documentfoundation.org/attachment.cgi?id=121808
[3] https://bugs.documentfoundation.org/show_bug.cgi?id=94004
[4] https://gerrit.libreoffice.org/18397/



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