Re: GSoC Proposal - SVG Export

[Carl Sorensen]

On 11/30/18, 8:40 PM, "lilypond-devel on behalf of Étienne Beaulé" 
<address@hidden on behalf of address@hidden> wrote:

    Hello all!
    
    I’m Étienne Beaulé and I’ve been making some changes to LilyPond. I am also 
the maintainer of the MediaWiki Score extension which allows embedded LilyPond 
on Wikipedia. I’m currently a bachelor student at the Université de Montréal 
studying computer science and mathematics, and Google Summer of Code caught my 
eye. I’d be interested in doing a project if a mentor is available.
    
    # Improving SVG score output

I think this is a great idea!
    
    ## Summary
    
    Scalable Vector Graphics (SVG) is a vector graphics format designed for use 
on the internet. LilyPond (LY) is a program which translates musical notation 
syntax into a graphics format, such as SVG. This format is important for web 
publishing, and as a vector format, is advantageous over Portable Network 
Graphics (PNG) file, of which is _de facto_ used in this application.

PNG is only used for snippets.  The real _de facto_ output of LilyPond is 
ps/pdf.  I would hate to lose that.
    
    LY already has SVG output, yet is somewhat broken in many factors. Namely 
in font handling with broken sky-lining #3778 and the use of musical symbols as 
text. Development in fixing these problems may offer changes in other backends. 
This project will focus on the use of musical symbols in SVG files and the 
positioning of text. I have previously submitted patches for text-positioning 
bugs.

I think this sounds like a great idea!
    
    ## Deliverables
    
    * Self-contained musical SVG files
    * Functioning text sky-lining in SVG
    * Grouping of text for better placement in SVG
    
    ## Timeline
    
    _This is the hard part… Non-comprehensive_
    
    * Analysis of incompatibilities between PostScript (PS) and SVG output
      Important to have a grip on this to not introduce bugs and to keep 
commonalities between backends
    * Deprecation of SVG fonts - embed font into SVG
    
    — —
    
    * Reduce size of SVG by enumerating used glyphs
    * Merge glyph functions for text and symbols
    
    — —
    
    * Implement use of `<tspan>` tags and Cascading Style Sheets (CSS) for text 
handling
      * Will require modification of PS backends

This causes me concern.  In general, I think the PS backend works well, and I 
would prefer not to have it changed to be consistent with some functionality 
that only affects the SVG backend.  But until I see more concrete proposals, I 
don't know whether I would be in favor of or opposed to the PS backend 
modifications.

      * Fix Horizontal Spacing of text
    * Fix SVG text sky-lining in conjunction with character size / spacing 
calculations

This is great!

I think that I would like to continue to have LilyPond use Pango.  I don't know 
how Pango would integrate with SVG, but I think that's the right approach.  I 
would not be in favor of creating and maintaining our own text spacing engine.

Thanks,

Carl