bugGNU Octave - Bugs: bug #48435, Document capabilities and failings...


bug #48435: Document capabilities and failings of each toolkit (gnuplot, fltk, qt)

Submitter:  Francesco Potortì <pot>
Submitted:  Thu 07 Jul 2016 10:40:43 AM UTC
Category:  Documentation Severity:  3 - Normal
Priority:  5 - Normal Item Group:  Feature Request
Status:  Confirmed Assigned to:  None
Originator Name:  Open/Closed:  * Open
Release:  * dev Operating System:  * GNU/Linux
Fixed Release:  None Planned Release:  None
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Thu 07 Jul 2016 11:28:11 PM UTC, comment #7: 

Dmitri, would you like to draft a table based on the comments here, and your perception of the weaknesses of qt?

Lachlan Andrew <lachlan>
Thu 07 Jul 2016 06:45:47 PM UTC, comment #6: 

In my opinion gnuplot (with cairo backends) has superior font handling capabilities.

Also things like line joint (e.g. at the axis corners) make plots look like throwbacks from the last century.


Dmitri A. Sergatskov <dasergatskov>
Thu 07 Jul 2016 05:10:49 PM UTC, comment #5: 

TeX markup has been resolved.  Onscreen and printing both work.  The deficiencies of OpenGL are transparency, single precision as far as I know.

Rik <rik5>
Group administrator
Thu 07 Jul 2016 04:49:03 PM UTC, comment #4: 

This should make clear that the default qt toolkit is suitable for most purposes (if that's indeed what we believe, otherwise why is it the default?)

The main limitations of the OpenGL toolkits that I'm aware of are transparency, TeX markup, and single-precision truncation. Others?

Mike Miller <mtmiller>
Group Member
Thu 07 Jul 2016 04:34:06 PM UTC, comment #3: 

Re-titled and re-opened bug report.

I would like to see a small section at the beginning of the graphics chapter that discusses the three toolkits and compares and contrasts what is working/not working in a tabular format.

For example, gnuplot is a very good choice on platforms like Macs that have trouble with multi-threaded applications.  That is not something that one can guess at.  And the OpenGL implementation of patches is more complete than gnuplot, except for transparency where it is less capable.

Rik <rik5>
Group administrator
Thu 07 Jul 2016 04:12:50 PM UTC, comment #2: 

Thanks, this is good news.

However, before closing the bug, I think that the inability of fltk to use transparency should be documented in the manual.

Francesco Potortì <pot>
Thu 07 Jul 2016 03:45:50 PM UTC, comment #1: 

There are multiple issues here.  First, transparency is not implemented for the OpenGL toolkits (fltk and qt).  This explains why you can't get onscreen or printed results with fltk.  This is a known defect and there is an existing bug report for it.

The interface to gnuplot has been much improved on the development branch which will become 4.2.0 in two months.  It now displays correctly onscreen, as well as printing correctly.  See the attached triangles.png file.

Since the one bug is already known, and this has been fixed on the development branch, I'm going to close this report.

Rik <rik5>
Group administrator
Thu 07 Jul 2016 10:40:43 AM UTC, original submission:  

The following code should produce two partially transparent,  overlapping triangles of different colours delimited by solid lines:

hold on
fill([0 2 1], [0 0 2], 'b', 'facealpha', 0.3)
fill([0 2 1], 1+[0 0 2], 'r', 'facealpha', 0.3)

Note that Postscript generally cannot handle transparency, so we are using X and SVG.

When using fltk:
- on X the triangles are completely transparent, no colour
- printing to svg is the same, and additionally the lines are dashed

When using gnuplot 5:
- on X the triangles are coloured as expected, but opaque
- printing to svg the result is as expected

The only way to obtain the expected result is to use gnuplot and print to SVG.

Francesco Potortì <pot>


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Attach Files:

Attached Files
file #37758:  triangles.png added by rik5 (31KiB - image/png)


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    Follow 9 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2016-07-07 lachlan Item GroupIncorrect Result Feature Request
    2016-07-07 rik5 CategoryPlotting with OpenGL Documentation
        StatusFixed Confirmed
        Open/ClosedClosed Open
        Release4.0.2 dev
        Summarytransparent patches can only be obtained by printing to svg with gnuplot Document capabilities and failings of each toolkit (gnuplot, fltk, qt)
    2016-07-07 rik5 Attached File- Added triangles.png, #37758
        StatusNone Fixed
        Open/ClosedOpen Closed

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