The beginnings of a layout system

elements/basic/container.go

@@ -0,0 +1,136 @@
+package basic
+
+import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/theme"
+import "git.tebibyte.media/sashakoshka/tomo/artist"
+import "git.tebibyte.media/sashakoshka/tomo/elements/core"
+
+type Container struct {
+	*core.Core
+	core core.CoreControl
+
+	layout     tomo.Layout
+	children   []tomo.LayoutEntry
+	selectable bool
+}
+
+func NewContainer (layout tomo.Layout) (element *Container) {
+	element = &Container { }
+	element.Core, element.core = core.NewCore(element)
+	element.SetLayout(layout)
+	return
+}
+
+func (element *Container) SetLayout (layout tomo.Layout) {
+	element.layout = layout
+	element.recalculate()
+}
+
+func (element *Container) Adopt (child tomo.Element, expand bool) {
+	child.SetParentHooks (tomo.ParentHooks {
+		MinimumSizeChange:
+			func (int, int) { element.updateMinimumSize() },
+		SelectabilityChange:
+			func (bool) { element.updateSelectable() },
+	})
+	element.children = append (element.children, tomo.LayoutEntry {
+		Element: child,
+	})
+
+	element.updateMinimumSize()
+	element.updateSelectable()
+	element.recalculate()
+	if element.core.HasImage() { element.draw() }
+}
+
+// Disown removes the given child from the container if it is contained within
+// it.
+func (element *Container) Disown (child tomo.Element) {
+	for index, entry := range element.children {
+		if entry.Element == child {
+			entry.SetParentHooks(tomo.ParentHooks { })
+			element.children = append (
+				element.children[:index],
+				element.children[index + 1:]...)
+				break
+		}
+	}
+
+	element.updateMinimumSize()
+	element.updateSelectable()
+	element.recalculate()
+	if element.core.HasImage() { element.draw() }
+}
+
+// Children returns a slice containing this element's children.
+func (element *Container) Children () (children []tomo.Element) {
+	children = make([]tomo.Element, len(element.children))
+	for index, entry := range element.children {
+		children[index] = entry.Element
+	}
+	return
+}
+
+// CountChildren returns the amount of children contained within this element.
+func (element *Container) CountChildren () (count int) {
+	return len(element.children)
+}
+
+// Child returns the child at the specified index. If the index is out of
+// bounds, this method will return nil.
+func (element *Container) Child (index int) (child tomo.Element) {
+	if index < 0 || index > len(element.children) { return }
+	return element.children[index].Element
+}
+
+func (element *Container) Handle (event tomo.Event) {
+	switch event.(type) {
+	case tomo.EventResize:
+		resizeEvent := event.(tomo.EventResize)
+		element.core.AllocateCanvas (
+			resizeEvent.Width,
+			resizeEvent.Height)
+		element.recalculate()
+		element.draw()
+	
+	// TODO:
+	}
+	return
+}
+
+func (element *Container) AdvanceSelection (direction int) (ok bool) {
+	// TODO:
+	return
+}
+
+func (element *Container) updateSelectable () {
+	selectable := false
+	for _, entry := range element.children {
+		if entry.Selectable() { selectable = true }
+	}
+	element.core.SetSelectable(selectable)
+}
+
+func (element *Container) updateMinimumSize () {
+	element.core.SetMinimumSize(element.layout.MinimumSize(element.children))
+}
+
+func (element *Container) recalculate () {
+	bounds := element.Bounds()
+	element.layout.Arrange(element.children, bounds.Dx(), bounds.Dy())
+}
+
+func (element *Container) draw () {
+	bounds := element.core.Bounds()
+
+	artist.Rectangle (
+		element.core,
+		theme.BackgroundImage(),
+		nil, 0,
+		bounds)
+
+	// TODO
+	for _, entry := range element.children {
+		artist.Paste(element.core, entry, entry.Position)
+	}
+}