SVG renders with poor precision

[gskluzacek]

New, to pycairo, so maybe I'm missing something...

I'm trying to draw a simple polygon with move_to & line_to, however the values appearing in the SVG output are only accurate to the 100th place.

for example:

  I give an x coordinate in the move_to call of 6.426575
             but it shows up in the SVG file as 6.425781

for some reason its loosing precision after 6.42, the next digit should be a 6, but I'm getting a 5.

here's my code:

import cairo
with cairo.SVGSurface("test_2.svg", 100, 100) as surface:
    context = cairo.Context(surface)
    context.set_line_width(.1)
    context.set_source_rgb(1, 0, 0)
    context.move_to(6.426575, 89.055378)
    context.line_to(65.205100, 3.311026)
    context.line_to(123.983626, 89.055378)
    context.close_path()
    context.stroke()

here is the svg output

<?xml version="1.0" encoding="UTF-8"?>
<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="100" height="100"
     viewBox="0 0 100 100">
    <path fill="none" stroke-width="0.1" stroke-linecap="butt" stroke-linejoin="miter" stroke="rgb(100%, 0%, 0%)"
          stroke-opacity="1" stroke-miterlimit="10"
          d="M 6.425781 89.054688 L 65.207031 3.3125 L 123.984375 89.054688 Z M 6.425781 89.054688 "/>
</svg>

[lazka]

I can confirm the result and I'm getting the same result with C, so this needs to be reported to cairo https://gitlab.freedesktop.org/cairo/cairo/-/issues

// cc -o cairo_svg cairo_svg.c $(pkg-config --cflags --libs cairo cairo-svg)
#include <cairo.h>
#include <cairo-svg.h>

int main(void) {
    cairo_surface_t *surface;
    cairo_t *context;

    surface = cairo_svg_surface_create("test_2.svg", 100, 100);
    context = cairo_create(surface);
    cairo_set_line_width(context, 0.1);
    cairo_set_source_rgb(context, 1, 0, 0);
    cairo_move_to(context, 6.426575, 89.055378);
    cairo_line_to(context, 65.205100, 3.311026);
    cairo_line_to(context, 123.983626, 89.055378);
    cairo_close_path(context);
    cairo_stroke(context);
    cairo_destroy(context);
    cairo_surface_destroy(surface);
    return 0;
}