jbosboom / svg-tiler Goto Github PK

Suppose we want to tile a chess position. The black and white pieces probably have the same shape, but differ in their color. Currently we'd have a mapping file like

K @white-king.svg
k @black-king.svg
Q @white-queen.svg
q @black-queen.svg

where the SVG files have the same paths with different stroke and fill colors. This duplication makes changing the shapes or colors unnecessarily difficult.

SVG supports CSS-like styles, and we should use them. I see two particular ways forward:

• Use CSS classes in the tile SVG files and specify a stylesheet on the command line, which will be embedded as a <style> element in the output SVG; the mapping file syntax will be extended to apply specified CSS classes to the <use> element referencing the symbol (e.g., K @white-king.svg; fill:white; stroke:black;).
• Extend the mapping file syntax to long names, then define other symbols as <g> elements with style attributes enclosing references to the previously-defined symbols (e.g., K <g fill="white" stroke="black"><use id="knight-template" /></g>). This still requires care when authoring the tile SVGs, as any styles specified in the symbol cannot be overridden at the <use> site. (There is syntax for referencing external files from <use> but I think the semantics are that of nested <svg> rather than <symbol> elements.)

Inkscape struggles to load some tiler outputs because they're large compared to many SVG files. We should remove empty <g> and <defs> elements, <metadata> elements on symbols (but they may contain license information about the included files), unreferenced symbols (or avoid emitting them entirely), and default attribute values and redundant namespace definitions (Batik loves these last two for some reason).

Would help interpret output while debugging, particularly when a mapping contains more characters than are actually used in a particular image.

Some care must be taken to sanitize the filenames. Also, we might map multiple characters to the same symbol. If they really are the same (not styled differently; see #1), we should only emit one symbol; otherwise we'll need unique names.

Inkscape doesn't handle (some) outputs of the tiler very well, typically duplicating each element dozens of times at varying offsets from their actual locations. This will be a problem for us if we want to use Inkscape's PDF+LaTeX export functionality to get nice-looking text.

My current hypothesis is that Inkscape gets confused by its own sodipodi-namespaced metadata, which it may not expect to survive enclosure in a <symbol>. (I can't reproduce the bug on files not containing sodipodi metadata, but I haven't tried very hard.)

If removing that metadata doesn't fix the problem, we should find an XML testcase reducer and find minimal tiler outputs that make Inkscape's rasterization differ from rsvg-convert's by more than N%.

Could we allow png files in addition to svg for individual tiles? Should just have to wrap them in an <image> tag, but would be nice to be automatic. This would be especially helpful for retro video games.