Made this crazy selection system

backends/x/entity.go

@@ -15,6 +15,7 @@ type entity struct {
 	minWidth      int
 	minHeight     int
 
+	selected      bool
 	layoutInvalid bool
 	isContainer   bool
 }
@@ -42,6 +43,11 @@ func (ent *entity) unlink () {
 	}
 	ent.parent = nil
 	ent.window = nil
+	
+	if element, ok := ent.element.(tomo.Selectable); ok {
+		ent.selected = false
+		element.HandleSelectionChange()
+	}
 }
 
 func (entity *entity) link (parent *entity) {
@@ -96,6 +102,14 @@ func (entity *entity) scrollTargetChildAt (point image.Point) *entity {
 	return nil
 }
 
+func (entity *entity) forMouseTargetContainers (callback func (tomo.MouseTargetContainer)) {
+	if entity.parent == nil { return }
+	if parent, ok := entity.parent.element.(tomo.MouseTargetContainer); ok {
+		callback(parent)
+	}
+	entity.parent.forMouseTargetContainers(callback)
+}
+
 // ----------- Entity ----------- //
 
 func (entity *entity) Invalidate () {
@@ -195,6 +209,14 @@ func (entity *entity) PlaceChild (index int, bounds image.Rectangle) {
 	child.InvalidateLayout()
 }
 
+func (entity *entity) SelectChild (index int, selected bool) {
+	child := entity.children[index]
+	if element, ok := entity.element.(tomo.Selectable); ok {
+		child.selected = selected
+		element.HandleSelectionChange()
+	}
+}
+
 func (entity *entity) ChildMinimumSize (index int) (width, height int) {
 	childEntity := entity.children[index]
 	return childEntity.minWidth, childEntity.minHeight
@@ -220,6 +242,12 @@ func (entity *entity) FocusPrevious () {
 	entity.window.system.focusPrevious()
 }
 
+// ----------- SelectableEntity ----------- //
+
+func (entity *entity) Selected () bool {
+	return entity.selected
+}
+
 // ----------- FlexibleEntity ----------- //
 
 func (entity *entity) NotifyFlexibleHeightChange () {

backends/x/event.go

@@ -206,12 +206,19 @@ func (window *window) handleButtonPress (
 		}
 	} else {
 		underneath := window.system.childAt(point)
+		window.system.drags[buttonEvent.Detail] = underneath
 		if child, ok := underneath.element.(tomo.MouseTarget); ok {
-			window.system.drags[buttonEvent.Detail] = child
 			child.HandleMouseDown (
 				point.X, point.Y,
 				input.Button(buttonEvent.Detail))
 		}
+		callback := func (container tomo.MouseTargetContainer) {
+			container.HandleChildMouseDown (
+				point.X, point.Y,
+				input.Button(buttonEvent.Detail),
+				underneath.element)
+		}
+		underneath.forMouseTargetContainers(callback)
 	}
 	
 	window.system.afterEvent()
@@ -223,12 +230,22 @@ func (window *window) handleButtonRelease (
 ) {
 	buttonEvent := *event.ButtonReleaseEvent
 	if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 { return }
-	child := window.system.drags[buttonEvent.Detail]
-	if child != nil {
-		child.HandleMouseUp (
+	dragging := window.system.drags[buttonEvent.Detail]
+	if dragging != nil {
+		if child, ok := dragging.element.(tomo.MouseTarget); ok {
+			child.HandleMouseUp (
+				int(buttonEvent.EventX),
+				int(buttonEvent.EventY),
+				input.Button(buttonEvent.Detail))
+		}
+		callback := func (container tomo.MouseTargetContainer) {
+			container.HandleChildMouseUp (
 			int(buttonEvent.EventX),
 			int(buttonEvent.EventY),
-			input.Button(buttonEvent.Detail))
+			input.Button(buttonEvent.Detail),
+			dragging.element)
+		}
+		dragging.forMouseTargetContainers(callback)
 	}
 	
 	window.system.afterEvent()
@@ -244,7 +261,7 @@ func (window *window) handleMotionNotify (
 
 	handled := false
 	for _, child := range window.system.drags {
-		if child, ok := child.(tomo.MotionTarget); ok {
+		if child, ok := child.element.(tomo.MotionTarget); ok {
 			child.HandleMotion(x, y)
 			handled = true
 		}

backends/x/system.go

@@ -33,7 +33,7 @@ type system struct {
 	drawingInvalid   entitySet
 	anyLayoutInvalid bool
 	
-	drags [10]tomo.MouseTarget
+	drags [10]*entity
 
 	pushFunc func (image.Rectangle)
 }