TAChart spline demo crashes with log axis
lazarus / 55-TAChart

----------------------------------------------------------------------
wp · 2011-10-05 19:58

Please find in the attachment a modified version of the "func" demo of
TAChart. On the spline page I added a checkbox to activate a
logarithmic transform for the y axis of ChartSpline.

However, the program crashes when the checkbox is clicked and the log
transform is activated. The crash occurs in "LineIntersectsRect"
because of calculating with -INF.

----------------------------------------------------------------------
Ask · 2011-10-10 09:59

I'd say this is a borderline case. The user asked TAChart to draw
negative values
on the logarithmic axis, which IMO is an error, and should be reported
as such.

On the other hand, cases like spline series are not so clear, because,
as you have demonstrated, spline may go below zero even if user's data
did not.

Partially fixed the issue in r32795 (there are still ways to cause
error, but it is much harder now).

----------------------------------------------------------------------
wp · 2011-10-10 21:45

Quoteas you have demonstrated, spline may go below zero even if user's
data did not
How would the calculated series (pimarily TSplineSeries and
TFitSeries) behave if the transformation's AxisToGraph would set the
function result of erroneous arguments to NaN? Wouldn't NaN be ignored
by the series for drawing?