Implement SVG in OT support.

[bruvzg]

Implements support for SVG emoji fonts.

• SVG is pre-processed using XMLParser to remove unrelated glyphs from the multi-glyph documents (first time glyph rendering might be slow with fonts that use large mult-glyph documets).
• Document view box is used only to determine aspect ratio, real viewbox is calculated from bounding boxes of top level elements.
• XMLParser is changed to accept external data pointer without making a copy (some fonts have a single 20MB SVG with all glyphs).

[fire]

@hermet

ThorVG, which is used by Godot to rasterize SVGs, seems to be unable to load SVGs without viewBox attribute and unable to get bounding box of the SVG objects.

Also, ThorVG unable to extract and rasterize part of SVG using object id, which might be necessary for some SVG fonts.

Some feedback.

[mgrudzinska]

@fire thanks for letting us know!
We'll try to solve the issues on the TVG side.
If you find any svg file which doesn't display as it should, please open issue in the ThorVG repo.

[bruvzg]

With some hacks, got it working.

[fire]

Is this ready to review / merge?

[bruvzg]

Is this ready to review / merge?

It is ready.

[akien-mga]

It doesn't seem to be implemented yet for the GDExtension builds of the TextServer. How do you envision it working? The multiple dependencies and separate module make it a bit tricky.

[bruvzg]

Added GDExtension build support and moved tvg_svginot code to the text servers.

SVG is pre-processed using XMLParser to remove unrelated glyphs from the multi-glyph documents (first time glyph rendering might be slow with fonts that use large mult-glyph documets).

This part is much slower with GDExtension, due to lack of += operators in String and unexposed XMLParser::_open_buffer.

[akien-mga]

If this is the exact same code in both modules, maybe we could avoid the duplication by allowing ourselves a relative include of the files in the other module? I.e. have text_server_fb code compile and look for ../text_server_adv/thorvg_svg_in_ot.h?

It's a bit dirty because it means that text_server_fb couldn't build if text_server_adv is deleted from the tree, but that might be better than fully duplicating the code?

Also, how is the current duplication handled if both modules are compiled together?

[bruvzg]

It's a bit dirty because it means that text_server_fb couldn't build if text_server_adv is deleted from the tree, but that might be better than fully duplicating the code?

For the header it's probably OK, but for the thorvg_svg_in_ot.cpp it might be an issue.
Edit: SCons will not accept the same file in the two places - scons: *** Two environments with different actions were specified for the same target:

Also, how is the current duplication handled if both modules are compiled together?

It's in the different compile units and is not used from any other code, so should not be an issue.

[akien-mga]

Looks good to me.

[akien-mga]

Thanks!