support transparency

[t-bltg]

Fix https://github.com/JuliaIO/Sixel.jl/issues/17.

PR (mlterm)

master

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[t-bltg]

@johnnychen94 ?

[t-bltg]

Regarding the tests, there is something fundamentally fishy with src/terminaltools.jl: query_terminal requires stdin fd to be opened, and under the tests, stdin is closed since tests are ran under non interactive mode, so testing is not representative. ==> side effect of https://github.com/JuliaLang/Pkg.jl/pull/3065.

I couldn't find a way to fake stdin when querying sixel support, so I'm a bit stuck here @johnnychen94.

[johnnychen94]

Why would you need the interactive mode to run the test? I mean, it's more or less like how https://github.com/JuliaIO/Sixel.jl/blob/07011d31c9308a29d58390fb83aa14268d1a21e1/test/backend/libsixel.jl#L60-L63 does for RGBA, right?

img = rand(RGBA, 5, 5)
io = IOBuffer()
sixel_encode(io, img)
@test ref == String(take!(io))

[t-bltg]

I got confused by https://github.com/JuliaIO/Sixel.jl/blob/07011d31c9308a29d58390fb83aa14268d1a21e1/test/runtests.jl#L9

[johnnychen94]

sixel_encode supports three outputs:

• sixel_encode(img): println to stdout. This requires interactive mode (actually not, but CI environment doesn't support sixel)
• sixel_encode(::IO, img)

It's okay to use IOBuffer to get the encoded sequence and test against it.

[t-bltg]

Last commit is optional, let me know I you don't want it.

[t-bltg]

Let's put this on hold since the real fix would (hopefully) be brought by https://github.com/libsixel/libsixel/pull/23.

I'm planning of bumping libsixel to 1.10.3 (https://github.com/JuliaPackaging/Yggdrasil/pull/5432 - might require running gen/generator.jl here).

[ctrlcctrlv]

@t-bltg Perhaps we should work together instead of separately, as I got a bit scared off by all the memory safety issues in libsixel so have been afraid to make big changes to the C code, especially because we know for a fact the current API's aren't even able to be made safe as a few of them lack critical information like data size.

I don't know Julia, sorry, but my longterm plan upstream has been to:

• switch the core library to another language, probably Rust if I were to be its main developer as that's the language I know best for systems programming;
• write a C ABI mimicking the existing C API.

[t-bltg]

That's certainly a good idea to transition to rust if you want something similar to current c interface. I must admit I never wrote rust code (lots of Fortran and C, and obviously julia) ;). But if I can help in any way ...