Move style into this repostiory

style/style.go

@@ -0,0 +1,70 @@
+package style
+
+import "image/color"
+import "git.tebibyte.media/tomo/tomo"
+
+// Style can apply a visual style to different objects.
+type Style struct {
+	// Rules determines which styles get applied to which Objects.
+	Rules []Rule
+
+	// Colors maps tomo.Color values to color.RGBA values.
+	Colors map[tomo.Color] color.Color
+}
+
+// Rule describes under what circumstances should certain style attributes be
+// active.
+type Rule struct {
+	Role tomo.Role
+	Tags []string
+	Set  AttrSet
+}
+
+// Ru is shorthand for creating a rule structure
+func Ru (set AttrSet, role tomo.Role, tags ...string) Rule {
+	return Rule {
+		Role: role,
+		Tags: tags,
+		Set:  set,
+	}
+}
+
+// AttrSet is a set of attributes wherein only one/zero of each attribute type
+// can exist. It is keyed by the AttrKind of each attribute and must not be
+// modified directly.
+type AttrSet map[tomo.AttrKind] tomo.Attr
+
+// AS builds an AttrSet out of a vararg list of Attr values. If multiple Attrs
+// of the same kind are specified, the last one will override the others.
+func AS (attrs ...tomo.Attr) AttrSet {
+	set := AttrSet { }
+	set.Add(attrs...)
+	return set
+}
+
+// Add adds attributes to the set.
+func (this AttrSet) Add (attrs ...tomo.Attr) {
+	for _, attr := range attrs {
+		this[attr.Kind()] = attr
+	}
+}
+
+// MergeUnder takes attributes from another set and adds them if they don't
+// already exist in this one.
+func (this AttrSet) MergeUnder (other AttrSet) {
+	if other == nil { return }
+	for _, attr := range other {
+		if _, exists := this[attr.Kind()]; !exists {
+			this.Add(attr)
+		}
+	}
+}
+
+// MergeOver takes attributes from another set and adds them, overriding this
+// one.
+func (this AttrSet) MergeOver (other AttrSet) {
+	if other == nil { return }
+	for _, attr := range other {
+		this.Add(attr)
+	}
+}