Upper before this PR, lower after.
This PR manually applies a MSAA to the font atlas. Before this PR, the
font may seem aliased ( espeacially on low DPI monitors ), that's
because `DirectWrite` and `CoreText` ( on which currently `Zed` built
the whole text system ) uses different anti-aliasing strategy. The
different anti-aliasing approach used by `DirectWrite` and `CoreText`:
The upper is `VSCode` font rendering result, middle `macOS`, lower this
PR ( pic captured with same font face, same font size, same DPI, same
physical resolution, same editor theme, and same magnification rate ).
This PR brings a quality similiar to `CoreText`. What's more, from the
`VSCode` image, you can see how `DirectWrite` sub-pixel anti-aliasing is
performed on the edge of the glyph. Can we achieve the same rendering
quality? Currently, No. `Zed` use a grayscale image to render glyph, and
a sub-pixel anti-aliasing `DirectWrite` requires all RGB channels and
the foreground color of the rendering glyph, which `Zed` dose not
provide.
So, to achieve the quality of `VSCode` font rendering, the text system
of `Zed` needs much much more efforts to refactor the codes.
Release Notes:
- N/A
张小白
c0259a448d