plotters-rs/plotters-svg

SVG Backend crate for Plotters

plotters-svg's Issues

svg draw_text do not preserve spaces

Hello,

this code

use plotters::prelude::*;

fn main() {

    let root_drawing_area = SVGBackend::new("images/0.1.svg", (1159, 539))
        .into_drawing_area();
    root_drawing_area.fill(&WHITE).unwrap();
    let text_style = TextStyle::from(("monospace", 25).into_font());
    root_drawing_area.draw_text("|___|___|", &text_style, (100,100)).unwrap();
    root_drawing_area.draw_text("|   |   |", &text_style, (100,150)).unwrap();
    root_drawing_area.draw_text("|   |   |", &text_style, (100,200)).unwrap();
}

produce next image:

while all vertical bars should be aligned.

Looks like the problem is in the svg text tag: If I change from

<text x="100" y="150" dy="0.76em" text-anchor="start" font-family="monospace" font-size="20.161290322580644" opacity="1" fill="#000000">
|   |   |
</text>

to

<text x="100" y="150" dy="0.76em" text-anchor="start" font-family="monospace" font-size="20.161290322580644" opacity="1" fill="#000000" xml:space="preserve">
|   |   |
</text>

(note xml:space="preserve" inside text tag) then it looks better

Test don't compile in copr

https://download.copr.fedorainfracloud.org/results/remilauzier/plotters/fedora-rawhide-x86_64/02251721-rust-plotters-svg/builder-live.log.gz

You can see at the end that the failed failed to compiled.

Dependabot couldn't fetch all your path-based dependencies

Dependabot couldn't fetch one or more of your project's path-based Rust dependencies. The affected dependencies were ../plotters/Cargo.toml.

To use path-based dependencies with Dependabot the paths must be relative and resolve to a directory in this project's source code.

View the update logs.

Reduce SVG size

For example this histogram is 13kB, while it could be 3kB (compressed via the first site i found):

In fact, looking at the XML code, it does look very repetitive.

<svg width="1152" height="648" viewBox="0 0 1152 648" xmlns="http://www.w3.org/2000/svg">
<rect x="0" y="0" width="1151" height="647" opacity="1" fill="#FFFFFF" stroke="none"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="81" y1="582" x2="81" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="113" y1="582" x2="113" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="146" y1="582" x2="146" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="179" y1="582" x2="179" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="212" y1="582" x2="212" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="244" y1="582" x2="244" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="277" y1="582" x2="277" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="310" y1="582" x2="310" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="343" y1="582" x2="343" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="376" y1="582" x2="376" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="408" y1="582" x2="408" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="441" y1="582" x2="441" y2="4"/>
<line opacity="0.1" stroke="#000000" stroke-width="1" x1="474" y1="582" x2="474" y2="4"/>
...

An example optimization is to make this line list a <path> instead (see also path commands):

<svg width="1152" height="648" viewBox="0 0 1152 648" xmlns="http://www.w3.org/2000/svg">
<rect x="0" y="0" width="1151" height="647" opacity="1" fill="#FFFFFF" stroke="none"/>
<path opacity="0.1" stroke="#000000" stroke-width="1" d="M81,582 V4 M113,582 V4 M146,582 V4 ..."/>

To enable this kind of optimizations, I suggest making SVGBackend work by appending SVG elements to an array, and only write to its output on DrawingBackend::present, so that this kind of pattern can be minified.

Willing to make a patch for this, what do you think?