Basic support in X backend for new API

backends/x/system.go

@@ -0,0 +1,109 @@
+package x
+
+import "image"
+import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/canvas"
+
+type entitySet map[*entity] struct { }
+
+func (set entitySet) Empty () bool {
+	return len(set) == 0
+}
+
+func (set entitySet) Has (entity *entity) bool {
+	_, ok := set[entity]
+	return ok
+}
+
+func (set entitySet) Add (entity *entity) {
+	set[entity] = struct { } { }
+}
+
+type system struct {
+	child   *entity
+	focused *entity
+	canvas  canvas.BasicCanvas
+
+	theme  tomo.Theme
+	config tomo.Config
+
+	invalidateIgnore bool
+	drawingInvalid   entitySet
+	anyLayoutInvalid bool
+
+	pushFunc func (image.Rectangle)
+}
+
+func (system *system) initialize () {
+	system.drawingInvalid = make(entitySet)
+}
+
+func (system *system) SetTheme (theme tomo.Theme) {
+	system.theme = theme
+	if system.child == nil { return }
+	if child, ok := system.child.element.(tomo.Themeable); ok {
+		child.SetTheme(theme)
+	}
+}
+
+func (system *system) SetConfig (config tomo.Config) {
+	system.config = config
+	if system.child == nil { return }
+	if child, ok := system.child.element.(tomo.Configurable); ok {
+		child.SetConfig(config)
+	}
+}
+
+func (system *system) resizeChildToFit () {
+	system.child.bounds        = system.canvas.Bounds()
+	system.child.clippedBounds = system.child.bounds
+	system.child.Invalidate()
+	if system.child.isContainer {
+		system.child.InvalidateLayout()
+	}
+}
+
+func (system *system) afterEvent () {
+	if system.anyLayoutInvalid {
+		system.layout(system.child, false)
+		system.anyLayoutInvalid = false
+	}
+	system.draw()
+}
+
+func (system *system) layout (entity *entity, force bool) {
+	if entity == nil { return }
+	if entity.layoutInvalid == true || force {
+		entity.element.(tomo.Container).Layout()
+		entity.layoutInvalid = false
+		force = true
+	}
+
+	for _, child := range entity.children {
+		system.layout(child, force)
+	}
+}
+
+func (system *system) draw () {
+	finalBounds := image.Rectangle { }
+
+	// ignore invalidations that result from drawing elements, because if an
+	// element decides to do that it really needs to rethink its life
+	// choices.
+	system.invalidateIgnore = true
+	defer func () { system.invalidateIgnore = false } ()
+
+	for entity := range system.drawingInvalid {
+		entity.element.Draw (canvas.Cut (
+			system.canvas,
+			entity.clippedBounds))
+		finalBounds = finalBounds.Union(entity.clippedBounds)
+	}
+	system.drawingInvalid = make(entitySet)
+
+	// TODO: don't just union all the bounds together, we can definetly
+	// consolidateupdated regions more efficiently than this.
+	if !finalBounds.Empty() {
+		system.pushFunc(finalBounds)
+	}
+}