Constant line arrow pointing down?
lazarus / 55-TAChart

----------------------------------------------------------------------
madepabloh · 2014-09-07 12:10

Constant line series of TAChart contains a propertie what is "Arrow"

However, it seems that it only points up. Is there a way to made it to
point down?

If not, may be it could be interesting to add a subpropertie to the
arrow to allow the user to select if to have the arrow pointing up,
down or both, in case of vertical lines, or left, right or both in
case of horizontal lines. Just only an idea!

Thanks!

----------------------------------------------------------------------
wp · 2014-09-07 12:24

QuoteIs there a way to made it to point down?I don't think so...

The basic idea behind the arrow is that of an axis line which has an
arrow at its end. However, if the axis direction is inverted the arrow
should be at the other end of the line pointing into the opposite
direction. This does not happen. Therefore, I'd classify this as a
bug. It certainly would not be so difficult to fix. There could be an
arrow property "Opposite" which does exactly that.

In this context, is there a need for a second arrow at the "starting"
point?

----------------------------------------------------------------------
wp · 2014-09-07 15:21

I forgot that there is already a property "Inverted" for TChartArrow
which I introduced for BiDiMode. It was not published because I did
not see its general applicability at that time. In the current trunk
version it is published now and it is respected when painting a
TConstantLine series.

----------------------------------------------------------------------
madepabloh · 2014-09-07 16:24

Thanks @wp!

----------------------------------------------------------------------
madepabloh · 2014-09-10 22:33

Let me explain why i need to have the arrow pointing to the other
side. May be it could clarify the necessity.

I have a line serie with values vs datetime. Date and time is on X
axis, and values in Y axis. However, some special events occurs at
selected dates. I would like to see the relation ship. For that
reason, i plot the line serie as usual, but i add a vertical constant
line at the date of the pecial event.  The arrow, pointing down will
capture the attention pointing to the date showed in the X axis.
Otherwise the arrow point to the top, where i do not have marks and
labels. I could add and axis to the top, but maybe is more easy and
nice to have the arrow pointing toward the bottom axis.

I hope now you could see why it could be interesting the issue of the
arrow.
Cheers,

----------------------------------------------------------------------
wp · 2014-09-10 22:51

Sure. If you use the trunk version of TAChart, you can flip the arrow
by means of the "Inverted" property from "----->" to "<------" (and
similar for the vertical lines, but this is more difficult to sketch
here).

----------------------------------------------------------------------
madepabloh · 2014-09-11 18:47

Thanks for the tip!