kiwi-go

Fast Go implementation of the Cassowary constraint solving algorithm, ported directly from LUME Kiwi.

go get github.com/unxed/kiwi-go

package main

import (
	"fmt"

	"github.com/unxed/kiwi-go"
)

func main() {
	solver := kiwi.NewSolver()

	left := kiwi.NewVariable("left")
	width := kiwi.NewVariable("width")
	right := kiwi.NewVariable("right")

	_ = solver.AddEditVariable(left, kiwi.StrengthStrong)
	_ = solver.AddEditVariable(width, kiwi.StrengthStrong)

	_ = solver.SuggestValue(left, 100)
	_ = solver.SuggestValue(width, 400)

	// right == left + width
	cn := kiwi.NewConstraint(right, kiwi.OpEq, left.Plus(width))
	_ = solver.AddConstraint(cn)

	solver.UpdateVariables()

	fmt.Printf("right = %f\n", right.Value()) // 500.0
}

kiwi-go includes a Discrete Cassowary Engine designed for Terminal User Interfaces (TUI), adapting concepts from font hinting (TrueType & FreeType):

• FreeType-style Autohinting (ApportionSum): Distributes rounding remainders using Hamilton / Hare-Niemeyer apportionment so that integer component sizes sum to container totals with zero character gaps or overflows, preserving layout symmetry.
• TrueType-style Rule Directives (RuleHinter): Apply explicit layout instructions such as SnapToGrid (for double-width CJK or grid boundaries), ClampMinMax, EqualizeGroup, and AlignEdges.
• DiscreteSolver: Integrates continuous Cassowary constraint solving, autohinting apportionment, and rule directives in a unified TUI layout solver.

For full mathematical design and TUI layout examples, see docs/DISCRETE_CASSOWARY.md.

Run the interactive TUI console demo:

go run ./cmd/kiwi-demo

Run unit tests:

go test -v ./...

Run benchmarks:

go test -bench=. ./...

First, ensure you have generated kiwi.wasm and wasm_exec.js using ./build.sh.

To run the NodeJS integration test, execute:

node test.js

You can also run the internal Go bridge tests using standard Go tools:

GOOS=js GOARCH=wasm go test -v .

To see the engine solving UI layouts in your browser:

1. Start a local web server in this directory (browsers do not allow fetching WASM from local file:// URLs due to CORS). For example:

   python3 -m http.server 8080

2. Open http://localhost:8080/index.html in your browser.
3. Resize the gray container box to see Cassowary dynamically calculate and apply layout constraints in real-time.

## License

Modified BSD License.