Lk

Lk is a GUI toolkit designed for Lcl.

It is a small, embeddable, retained-mode UI toolkit with Tk's ergonomics and McCLIM's presentation/command semantics.

Strict C89, no dependencies for the core, an optional SDL3 backend, and optional (but canonical) bindings to the Lcl scripting language with a declarative Layer‑2 DSL.

Version 0.1.0 -- pre-release. MIT.

app "Hello" #{width 320 height 160} {
    translator pointer_down greet Greet
    on Greet [lambda {cmd} { puts "hello, [get [get $cmd args] 0]" }]

    view {
        column "main" #{padding 12 gap 8} {
            label "l" #{text "A button that presents a value:"}
            button "b" #{text "Greet" focusable 1 present (greet (world))}
        }
    }
}

Basic Idea

McCLIM meets Tk.

The host rebuilds a tree of nodes with stable string ids every frame; lk diffs it against the previous frame and keeps per-node state (cursor, scroll, selection) across the diff.

Nodes can present typed values; translators turn gestures on presentations into commands -- the app handles commands, never raw callbacks.

Application-owned objects (documents, editors, images, canvases) are referenced from the tree through typed resource refs, so the tree stays data.

Build

cmake -B build && cmake --build build          # core + tests
build/lk_test

cmake -B build -DLK_BUILD_LCL=ON               # + Lcl bindings, DSL, runner
cmake --build build
build/lcl_lk_test                              # binding tests + doctests
build/lcl_lk_main examples/tour-dsl.lcl        # needs SDL3 + SDL3_ttf

License

MIT -- see LICENSE.