Lua d2dlist API

[Aurumaker72]

Rationale

Lua-to-C calls are relatively slow and should ideally be avoided in hot paths.

Drawing routines, regardles of their usage of either wgui or d2d, incur overhead from them.

Proposal

A thin abstraction for D2D should be introduced, in which commands can be encode as opcodes and have accompanying parameters.

Lua scripts utilizing this new API would only need to call one function and provide it a list of commands.

d2d.atdrawd2d(function()
    d2d.execute_list({
        {
            d2d.FILL_RECT, -- Opcode as integer constant
            4278190080, -- Color as raw integer
            0, -- Left
            0, -- Top
            100, -- Right
            150, -- Bottom
        }
    })
end)

Pros and Cons

• General performance improvement
• C side can perform various optimizations on the display list prior to D2D handoff

---

• Another drawing API
• Needs prototype+measuring to determine if perf difference justifies working on this

[jgcodes2020]

Suggestion: include an API for generating draw lists (similar to https://docs.rs/vello/latest/vello/struct.Scene.html)