Geometry Boost List: Re: [geometry] Problems with svg mapper

Subject: Re: [geometry] Problems with svg mapper
From: Barend Gehrels (barend_at_[hidden])
Date: 2014-10-14 14:08:34

Hi Volker,

Volker Schöch wrote On 14-10-2014 19:09:
>
> Hi Team,
>
> Thank you for pointing me to boost::geometry::svg_mapper, and to 
> Inkscape, which are valuable tools for debugging polygons. Based on 
> the example from the documentation ...
>
> http://www.boost.org/doc/libs/1_56_0/libs/geometry/doc/html/geometry/reference/io/svg/svg_mapper.html 
>
>
> ... I find the following oddity: Simply change the following line
>
> typedef boost::geometry::model::d2::point_xy<*double*> point_type;
>
> into
>
> typedef boost::geometry::model::d2::point_xy<*int*> point_type;
>
> Nota bene: All values in the example code are integral numbers, 
> anyway. Yet, the resulting output is different, see attached files. In 
> case of int, the entire graphic is considerably offset to the north.
>
> Should this be filed as a bug in boost trac?
>

I see it. Did not look for the cause yet. Yes, please file as a bug.

> Further modification of the original example leads to more serious 
> problems:
>
> std::ostringstreamsvg;
>
> // Specify the basic type
>
> typedefboost::geometry::model::d2::point_xy<int> point_type;
>
> // Declare some geometries and set their values
>
> point_typea;
>
> boost::geometry::assign_values(a, -100, -100);
>
> // Declare a stream and an SVG mapper
>
> boost::geometry::svg_mapper<point_type> mapper(svg, 1000, 1000);
>
> // Add geometries such that all these geometries fit on the map
>
> mapper.add(a);
>
> // Draw the geometries on the SVG map, using a specific SVG style
>
> mapper.map(a, 
> "fill-opacity:0.5;fill:rgb(153,204,0);stroke:rgb(153,204,0);stroke-width:2", 
> 5);
>
> // Destructor of map will be called - adding </svg>
>
> // Destructor of stream will be called, closing the file
>
> This code crashes with an obscure (for me) exception deep in the 
> callstack:
>
> Unhandled exception at 0x000007FEFD62940D in POWERPNT.EXE: Microsoft 
> C++ exception: boost::numeric::negative_overflow at memory location 
> 0x00000000001E9D60.
>
> (For the call stack, see the attached txt file.)
>
> Should this be filed as a (separate) issue in boost trac?
>

For me it does not crash but the resulting svg is not OK. Yes, please 
file this too. I know the cause but it is good to have it filed such 
that we can work on it in a structured way.

Thanks, Barend