Re: deafault arrow style (head length) in plots with vectors

[JoanPau <jo...@gm...>]

JoanPau wrote:
> 
> 
> Ethan Merritt wrote:
>> 
>> 
>> They are set by this routine in gadgets.c:
>> 
>> void
>> default_arrow_style(struct arrow_style_type *arrow)
>> {
>>     static const struct lp_style_type tmp_lp_style =
>> DEFAULT_LP_STYLE_TYPE;
>> 
>>     arrow->layer = 0;
>>     arrow->lp_properties = tmp_lp_style;
>>     arrow->head = 1;
>>     arrow->head_length = 0.0;
>>     arrow->head_lengthunit = first_axes;
>>     arrow->head_angle = 15.0;
>>     arrow->head_backangle = 90.0;
>>     arrow->head_filled = 0;
>> }
>> 
>> 
> 
> I can understand all the options but one. What does a 0.0 head_length
> mean?
> I thought that this would imply the same as nohead (any arrow drawn), but
> obviously I was wrong.
> Maybe it should be mentioned in the arrowstyle doc entry.
> 

This example with only one vecotr may illustrate the (not self explanatory)
behavior of a zero head length. The data.gnuplot has only one line of text
with the coordinates of the vector:

         0.0 0.0 1.0 1.0

And these are the commands (the range commands only to better visualize the
vector in the plot)

set xrange [-2:2]
set yrange [-2:2]
plot './data.gnuplot' w vectors
plot './data.gnuplot' w vectors size 0,45
plot './data.gnuplot' w vectors size 0.5,45

As you can see, head is drawn with a non 0 length in the first and second
case, and in the second the angle is ignored. In addition, and correct me 
if I misunderstand something, the head braces are not drawn in first_axes (x
axis) units, since they do not change their length when the plot is resized
or zoomed (for example interacting with the plot window).
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