[Octave-bug-tracker] [bug #41932] Solid line appears dashed with FLTK

[Rik]

Follow-up Comment #4, bug #41932 (project octave):

I think the problem lies with OpenGL.  I did some research and  OpenGL itself
only supports a limited range of line widths.  It has one range for aliased
(jagged) lines and another range for anti-aliased (smooth) lines.

I've attached code which will print out these ranges.  Unfortunately it's in C
so you need to have the development packages for GL, GLU, and GLUT installed. 
On Linux it compiles with


gcc -o rpt_lwidth rpt_lwidth.c -lGL -lGLU -lglut


In my case, the range of smooth lines is 1.0-5.0 and the granularity is 0.5 so
I can construct lines from 0.5-5.5.

It would be useful if someone who is having this "dashed" line issue could
compile and run the rpt_lwidth program.  My hunch is that the minimum smooth
line width might be greater than 1.

If this is the case, then we might be able to implement a solution in Octave
by querying these values.  If the user requests a line width that is too small
we could just substitute the minimum.  This may be what Matlab does which
could explain why they are always able to draw lines, even if the width is
specified as 0.5.


(file #31216)
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Additional Item Attachment:

File name: rpt_lwidth.c                   Size:0 KB


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