backend/internal/system/style.go

package system

import "git.tebibyte.media/tomo/tomo"
import "git.tebibyte.media/tomo/backend/style"

type styleApplicator struct {
	style      *style.Style
	role       tomo.Role
	rules      []style.Rule
	currentSet style.AttrSet
}

func (this *styleApplicator) apply (box anyBox) {
	if box.Role() != this.role {
		this.role = box.Role()
		// the role has changed, so re-cache the list of rules
		this.rules = nil
		for _, rule := range this.style.Rules {
			role := box.Role()
			// blank fields match anything
			if rule.Role.Package == "" { role.Package = "" }
			if rule.Role.Object  == "" { role.Object  = "" }
			if rule.Role == role {
				this.rules = append(this.rules, rule)
			}
		}
	}

	// compile list of attributes by searching through the cached ruleset
	attrs := make(style.AttrSet)
	for _, rule := range this.rules {
		satisifed := true
		for _, tag := range rule.Tags {
			if !box.Tag(tag) {
				satisifed = false
				break
			}
		}

		if satisifed {
			attrs.MergeOver(rule.Set)
		}
	}

	// reset an attribute if it is no longer specified
	if this.currentSet != nil {
		for kind := range this.currentSet {
			_, exists := attrs[kind]
			if !exists {
				box.unsetAttr(kind, false)
			}
		}
	}

	// apply that list of attributes
	this.currentSet = attrs
	for _, attr := range attrs {
		box.setAttr(attr, false)
	}
}