Thanks. That explains why OSs use the GPU for rendering windows and effects, but it's still not clear to me why a code editor would do the same. The features you list (transparency, glass effects, shadowing, window management, etc.) seem to be outside the purview of a text editor.

If you're saying that Zed is built on something like Skia, then it would already be cross-platform and not have to worry about Vulkan vs. DirectX, right?

> but it's still not clear to me why a code editor would do the same.

Happy to elaborate further.

Old school text rendering began with a table of character codes to actual, fixed-size bitmaps (this was a font), and rendering was straightforward: divide the framebuffer resolution by the bitmap resolution, clip/wrap the remaining, just place the bitmaps into the resultant grid, and pipe the framebuffer to the display. Done.

Nowadays, text editors don't just have text; they have markup like highlighting and syntax colouring (with 24-bit deep-colour, rather than the ANSI 16 colour codes), go-to, version control annotations, debug breakpoints, hover annotations, and in the case of 'notebooks' like Python notebooks, may have embedded media like images, videos, and even 3D renders. Many editor features may open pop-up windows or dialogue boxes, which will probably occlude the text 'behind'.

Now, most modern text editors also expect to work with non-bitmapped, non-monospaced typefaces in OpenType or TrueType format. These are complex beasts of their own with hinting, ligatures, variable weights, and more, and may even embed entire programs. They are usually Bezier/polynomial splines that the GPU can rasterise easily in hardware (no special shader required). After this rasterisation, any reasonable text editor will apply anti-aliasing, which is also work delegated to the GPU. There is probably a different algorithm for text (which needs to account for display subpixel layouts) versus UI elements (which may not).

The point I am driving at is that the proliferation of features expected from a modern text editor means that using a GPU for all of this is a natural evolution. As users, we may think 'it's just text' but from the perspective of the developer or the hardware, text and a ray-traced 3D game is no different: it's one 4D square matrix multiplied by another, one after another, and in the end reduced into a three-vector, representing the colour of a pixel.

> If you're saying that Zed is built on something like Skia, then it would already be cross-platform and not have to worry about Vulkan vs. DirectX, right?

Absolutely, because Skia handles that for the developer. And I suspect the reason why Zed didn't use Skia in the first place is ideological (Skia is by Google, written in C++), together with wanting to write 'the whole world' in Rust.