From 8858a54b5ddb3a2d8a42ecb1a837c02800bc934f Mon Sep 17 00:00:00 2001
From: Sam Anthony <sam@samanthony.xyz>
Date: Mon, 2 Mar 2026 17:38:55 -0500
Subject: create lay/strain package

The lay/strain package uses the Cassowary algorithm to solve systems of
layout constraints.
---
 lay/strain/sym.go | 70 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 70 insertions(+)
 create mode 100644 lay/strain/sym.go

(limited to 'lay/strain/sym.go')

diff --git a/lay/strain/sym.go b/lay/strain/sym.go
new file mode 100644
index 0000000..cf8777b
--- /dev/null
+++ b/lay/strain/sym.go
@@ -0,0 +1,70 @@
+package strain
+
+import (
+	"image"
+
+	"github.com/lithdew/casso"
+)
+
+// SymPt is a set of Cassowary symbols representing an image.Point.
+type SymPt struct {
+	X, Y casso.Symbol
+}
+
+// SymRect is a set of Cassowary symbols representing an
+// image.Rectangle.
+type SymRect struct {
+	Min, Max SymPt
+}
+
+func NewSymPt() SymPt {
+	return SymPt{casso.New(), casso.New()}
+}
+
+func NewSymRect() SymRect {
+	return SymRect{NewSymPt(), NewSymPt()}
+}
+
+// editRect marks all symbols of a rectangle as editable with a
+// certain precedence.
+func editRect(solver *casso.Solver, sr SymRect, p casso.Priority) error {
+	if err := editPt(solver, sr.Min, p); err != nil {
+		return err
+	}
+	if err := editPt(solver, sr.Max, p); err != nil {
+		return err
+	}
+	return nil
+}
+
+// editRect marks both symbols of a point as editable with a certain
+// precedence.
+func editPt(solver *casso.Solver, sp SymPt, p casso.Priority) error {
+	if err := solver.Edit(sp.X, p); err != nil {
+		return err
+	}
+	if err := solver.Edit(sp.Y, p); err != nil {
+		return err
+	}
+	return nil
+}
+
+func suggestRect(solver *casso.Solver, sr SymRect, r image.Rectangle) error {
+	if err := suggestPt(solver, sr.Min, r.Min); err != nil {
+		return err
+	}
+	if err := suggestPt(solver, sr.Max, r.Max); err != nil {
+		return err
+	}
+	return nil
+}
+
+func suggestPt(solver *casso.Solver, sp SymPt, p image.Point) error {
+	if err := solver.Suggest(sp.X, float64(p.X)); err != nil {
+		return err
+	}
+	if err := solver.Suggest(sp.Y, float64(p.Y)); err != nil {
+		return err
+	}
+	return nil
+}
-- 
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