vger-rs VS glyphy

I've done a library for vector graphics on the GPU which works pretty well for my uses:

https://github.com/audulus/vger

and a rust version:

https://github.com/audulus/vger-rs

(which powers my rust GUI library: https://github.com/audulus/rui)

Here's the approach for rendering path fills. From the readme:

> The bezier path fill case is somewhat original. To avoid having to solve quadratic equations (which has numerical issues), the fragment function uses a sort-of reverse Loop-Blinn. To determine if a point is inside or outside, vger tests against the lines formed between the endpoints of each bezier curve, flipping inside/outside for each intersection with a +x ray from the point. Then vger tests the point against the area between the bezier segment and the line, flipping inside/outside again if inside. This avoids the pre-computation of Loop-Blinn, and the AA issues of Kokojima.

It works pretty well, and doesn't require as much preprocessing as the code in the article. Also doesn't require any GPU compute (though I do use GPU compute for some things). I think ultimately the approach in the article (essentially Piet-metal, aka tessellating and binning into tiles) will deliver better performance, and support more primitives, but at greater implementation complexity. I've tried the Piet-metal approach myself and it's tricky! I like the simpler Shadertoy/SDF inspired approach :)

harfbuzz creator made https://github.com/behdad/glyphy/ which i integrated into GTK a while back (but we don't ship currently, because we still do the bitmap stuff).

the bitmap stuff still has major drawbacks though, like maintaining grid alignments and pixel boundaries where as this stuff (mostly) goes away using glyphy.

still work to be done around hinting though (hence not merged).

You can approximate the Bézier curves with circular arcs and store those in the "SDF" instead. https://github.com/behdad/glyphy

> The only issue with it is that font rendering looks horrific, but that might just be my machine.

This is because GTK4 enables pixel/scaling-independent fractional vertical positioning, even with hinting enabled. There's a long (somewhat ongoing) discussion at https://gitlab.gnome.org/GNOME/gtk/-/issues/3787, though I haven't followed the last few months of discussion.

Even though GTK4 aims to achieve scale-independent layout, the 4 horizontal/vertical positions still produce a bit of judder, and fonts do not scale smoothly (even with bilinear interpolation) with hinting enabled, and (unless fixed) there are rendering issues due to failing to clear the texture atlas properly: https://gitlab.gnome.org/GNOME/gtk/-/issues/4322

Interestingly there's a proposal to switch GTK4 fonts to SDF-style rendering. This is somewhat like what Qt Quick 2 implemented already (and KDE turns off and reverts to FreeType rendering, to make QML apps mimic Qt Widgets font rendering more): https://blogs.gnome.org/chergert/2022/03/20/rendering-text-w... However, I looked at https://github.com/behdad/glyphy and it seems to implement vector-based SDFs, instead of earlier texture-based SDF/MSDFs used by Valve games and Qt Quick.