Merge pull request 'atomize-element-interface' (#2) from atomize-element-interface into main

Reviewed-on: sashakoshka/tomo#2

artist/text.go

@@ -16,6 +16,7 @@ type characterLayout struct {
 type wordLayout struct {
 	position   image.Point
 	width      int
+	spaceAfter int
 	text       []characterLayout
 }
 
@@ -160,6 +161,25 @@ func (drawer *TextDrawer) LineHeight () (height fixed.Int26_6) {
 	return
 }
 
+// ReccomendedHeightFor returns the reccomended max height if the text were to
+// have its maximum width set to the given width. This does not alter the
+// drawer's state.
+func (drawer *TextDrawer) ReccomendedHeightFor (width int) (height int) {
+	if !drawer.layoutClean { drawer.recalculate() }
+	metrics := drawer.face.Metrics()
+	dot := fixed.Point26_6 { 0, 0 }
+	for _, word := range drawer.layout {
+		dot.X += fixed.Int26_6((word.width + word.spaceAfter) << 6)
+		
+		if word.width + word.position.X > width && word.position.X > 0 {
+			dot.Y += metrics.Height
+			dot.X = fixed.Int26_6(word.width << 6)
+		}
+	}
+
+	return dot.Y.Round()
+}
+
 func (drawer *TextDrawer) recalculate () {
 	drawer.layoutClean = true
 	drawer.layout = nil
@@ -219,9 +239,6 @@ func (drawer *TextDrawer) recalculate () {
 			dot.X = wordWidth
 		}
 
-		// add the word to the layout
-		drawer.layout = append(drawer.layout, word)
-
 		// skip over whitespace, going onto a new line if there is a
 		// newline character
 		for index < len(drawer.runes) && unicode.IsSpace(drawer.runes[index]) {
@@ -233,6 +250,7 @@ func (drawer *TextDrawer) recalculate () {
 				index ++
 			} else {
 				_, advance, ok := drawer.face.GlyphBounds(character)
+				word.spaceAfter = advance.Round()
 				index ++
 				if !ok { continue }
 				
@@ -246,6 +264,9 @@ func (drawer *TextDrawer) recalculate () {
 			}
 		}
 
+		// add the word to the layout
+		drawer.layout = append(drawer.layout, word)
+
 		// if there is a set maximum height, and we have crossed it,
 		// stop processing more words. and remove any words that have
 		// also crossed the line.

backends/x/event.go

@@ -27,6 +27,8 @@ func (window *Window) handleConfigureNotify (
 	connection *xgbutil.XUtil,
 	event xevent.ConfigureNotifyEvent,
 ) {
+	if window.child == nil { return }
+
 	configureEvent := *event.ConfigureNotifyEvent
 	
 	newWidth  := int(configureEvent.Width)
@@ -66,33 +68,20 @@ func (window *Window) handleKeyPress (
 		NumberPad: numberPad,
 	}
 
-	keyDownEvent := tomo.EventKeyDown {
+	if key == tomo.KeyTab && modifiers.Alt {
-		Key: key,
+		if child, ok := window.child.(tomo.Selectable); ok {
-		Modifiers: modifiers,
+			direction := tomo.SelectionDirectionForward
-		Repeated: false, // FIXME: return correct value here
+			if modifiers.Shift {
-	}
+				direction = tomo.SelectionDirectionBackward
-
-	if keyDownEvent.Key == tomo.KeyTab && keyDownEvent.Modifiers.Alt {
-		if window.child.Selectable() {
-			direction := 1
-			if keyDownEvent.Modifiers.Shift {
-				direction = -1
 			}
 
-			window.advanceSelectionInChild(direction)
+			if !child.HandleSelection(direction) {
+				child.HandleDeselection()
+			}
 		}
-	} else {
+	} else if child, ok := window.child.(tomo.KeyboardTarget); ok {
-		window.child.Handle(keyDownEvent)
+		// FIXME: pass correct value for repeated
-	}
+		child.HandleKeyDown(key, modifiers, false)
-}
-
-func (window *Window) advanceSelectionInChild (direction int) {
-	if window.child.Selected() {
-		if !window.child.AdvanceSelection(direction) {
-			window.child.Handle(tomo.EventDeselect { })
-		}
-	} else {
-		window.child.Handle(tomo.EventSelect { })
 	}
 }
 
@@ -116,10 +105,9 @@ func (window *Window) handleKeyRelease (
 		NumberPad: numberPad,
 	}
 	
-	window.child.Handle (tomo.EventKeyUp {
+	if child, ok := window.child.(tomo.KeyboardTarget); ok {
-		Key: key,
+		child.HandleKeyUp(key, modifiers)
-		Modifiers: modifiers,
+	}
-	})
 }
 
 func (window *Window) handleButtonPress (
@@ -128,48 +116,54 @@ func (window *Window) handleButtonPress (
 ) {
 	if window.child == nil { return }
 	
-	buttonEvent := *event.ButtonPressEvent
+	if child, ok := window.child.(tomo.MouseTarget); ok {
-	if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 {
+		buttonEvent := *event.ButtonPressEvent
-		sum := scrollSum { }
+		if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 {
-		sum.add(buttonEvent.Detail)
+			sum := scrollSum { }
-		window.compressScrollSum(buttonEvent, &sum)
+			sum.add(buttonEvent.Detail)
-		window.child.Handle (tomo.EventScroll {
+			window.compressScrollSum(buttonEvent, &sum)
-			X: int(buttonEvent.EventX),
+			child.HandleScroll (
-			Y: int(buttonEvent.EventY),
+				int(buttonEvent.EventX),
-			ScrollX: sum.x,
+				int(buttonEvent.EventY),
-			ScrollY: sum.y,
+				float64(sum.x), float64(sum.y))
-		})
+		} else {
-	} else {
+			child.HandleMouseDown (
-		window.child.Handle (tomo.EventMouseDown {
+				int(buttonEvent.EventX),
-			Button: tomo.Button(buttonEvent.Detail),
+				int(buttonEvent.EventY),
-			X: int(buttonEvent.EventX),
+				tomo.Button(buttonEvent.Detail))
-			Y: int(buttonEvent.EventY),
+		}
-		})
 	}
+	
 }
 
 func (window *Window) handleButtonRelease (
 	connection *xgbutil.XUtil,
 	event xevent.ButtonReleaseEvent,
 ) {
-	buttonEvent := *event.ButtonReleaseEvent
+	if window.child == nil { return }
-	if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 { return }
+	
-	window.child.Handle (tomo.EventMouseUp {
+	if child, ok := window.child.(tomo.MouseTarget); ok {
-		Button: tomo.Button(buttonEvent.Detail),
+		buttonEvent := *event.ButtonReleaseEvent
-		X: int(buttonEvent.EventX),
+		if buttonEvent.Detail >= 4 && buttonEvent.Detail <= 7 { return }
-		Y: int(buttonEvent.EventY),
+		child.HandleMouseUp (
-	})
+			int(buttonEvent.EventX),
+			int(buttonEvent.EventY),
+			tomo.Button(buttonEvent.Detail))
+	}
 }
 
 func (window *Window) handleMotionNotify (
 	connection *xgbutil.XUtil,
 	event xevent.MotionNotifyEvent,
 ) {
-	motionEvent := window.compressMotionNotify(*event.MotionNotifyEvent)
+	if window.child == nil { return }
-	window.child.Handle (tomo.EventMouseMove {
+	
-		X: int(motionEvent.EventX),
+	if child, ok := window.child.(tomo.MouseTarget); ok {
-		Y: int(motionEvent.EventY),
+		motionEvent := window.compressMotionNotify(*event.MotionNotifyEvent)
-	})
+		child.HandleMouseMove (
+			int(motionEvent.EventX),
+			int(motionEvent.EventY))
+	}
 }
 
 

backends/x/window.go

@@ -78,7 +78,11 @@ func (backend *Backend) NewWindow (
 func (window *Window) Adopt (child tomo.Element) {
 	if window.child != nil {
 		child.SetParentHooks (tomo.ParentHooks { })
-		if child.Selected() { child.Handle(tomo.EventDeselect { }) }
+		if previousChild, ok := window.child.(tomo.Selectable); ok {
+			if previousChild.Selected() {
+				previousChild.HandleDeselection()
+			}
+		}
 	}
 	window.child = child
 	if child != nil {
@@ -88,7 +92,6 @@ func (window *Window) Adopt (child tomo.Element) {
 			SelectionRequest: window.childSelectionRequestCallback,
 		})
 		
-		if child.Selectable() { child.Handle(tomo.EventSelect { }) }
 		window.resizeChildToFit()
 	}
 	window.childMinimumSizeChangeCallback(child.MinimumSize())
@@ -199,12 +202,18 @@ func (window *Window) redrawChildEntirely () {
 
 func (window *Window) resizeChildToFit () {
 	window.skipChildDrawCallback = true
-	window.child.Handle(tomo.EventResize {
+	if child, ok := window.child.(tomo.Expanding); ok {
-		Width:  window.metrics.width,
+		minimumHeight := child.MinimumHeightFor(window.metrics.width)
-		Height: window.metrics.height,
+		_, minimumWidth := child.MinimumSize()
-	})
+		window.childMinimumSizeChangeCallback (
+			minimumWidth, minimumHeight)
+	} else {
+		window.child.Resize (
+			window.metrics.width,
+			window.metrics.height)
+			window.redrawChildEntirely()
+	}
 	window.skipChildDrawCallback = false
-	window.redrawChildEntirely()
 }
 
 func (window *Window) childDrawCallback (region tomo.Canvas) {
@@ -246,7 +255,9 @@ func (window *Window) childMinimumSizeChangeCallback (width, height int) {
 }
 
 func (window *Window) childSelectionRequestCallback () (granted bool) {
-	window.child.Handle(tomo.EventSelect { })
+	if child, ok := window.child.(tomo.Selectable); ok {
+		child.HandleSelection(tomo.SelectionDirectionNeutral)
+	}
 	return true
 }
 

canvas.go

@@ -4,8 +4,9 @@ import "image"
 import "image/draw"
 import "image/color"
 
-// Canvas is like Image but also requires Set and SetRGBA methods. This
+// Canvas is like draw.Image but is also able to return a raw pixel buffer for
-// interface can be easily satisfied using an image.RGBA struct.
+// more efficient drawing. This interface can be easily satisfied using a
+// BasicCanvas struct.
 type Canvas interface {
 	draw.Image
 	Buffer () (data []color.RGBA, stride int)

element.go

@@ -0,0 +1,175 @@
+package tomo
+
+// ParentHooks is a struct that contains callbacks that let child elements send
+// information to their parent element without the child element knowing
+// anything about the parent element or containing any reference to it. When a
+// parent element adopts a child element, it must set these callbacks.
+type ParentHooks struct {
+	// Draw is called when a part of the child element's surface is updated.
+	// The updated region will be passed to the callback as a sub-image.
+	Draw func (region Canvas)
+
+	// MinimumSizeChange is called when the child element's minimum width
+	// and/or height changes. When this function is called, the element will
+	// have already been resized and there is no need to send it a resize
+	// event.
+	MinimumSizeChange func (width, height int)
+	
+	// SelectionRequest is called when the child element element wants
+	// itself to be selected. If the parent element chooses to grant the
+	// request, it must send the child element a selection event and return
+	// true.
+	SelectionRequest func () (granted bool)
+}
+
+// RunDraw runs the Draw hook if it is not nil. If it is nil, it does nothing.
+func (hooks ParentHooks) RunDraw (region Canvas) {
+	if hooks.Draw != nil {
+		hooks.Draw(region)
+	}
+}
+
+// RunMinimumSizeChange runs the MinimumSizeChange hook if it is not nil. If it
+// is nil, it does nothing.
+func (hooks ParentHooks) RunMinimumSizeChange (width, height int) {
+	if hooks.MinimumSizeChange != nil {
+		hooks.MinimumSizeChange(width, height)
+	}
+}
+
+// RunSelectionRequest runs the SelectionRequest hook if it is not nil. If it is
+// nil, it does nothing.
+func (hooks ParentHooks) RunSelectionRequest () (granted bool) {
+	if hooks.SelectionRequest != nil {
+		granted = hooks.SelectionRequest()
+	}
+	return
+}
+
+// Element represents a basic on-screen object.
+type Element interface {
+	// Element must implement the Canvas interface. Elements should start
+	// out with a completely blank buffer, and only allocate memory and draw
+	// on it for the first time when sent an EventResize event.
+	Canvas
+
+	// MinimumSize specifies the minimum amount of pixels this element's
+	// width and height may be set to. If the element is given a resize
+	// event with dimensions smaller than this, it will use its minimum
+	// instead of the offending dimension(s).
+	MinimumSize () (width, height int)
+
+	// Resize resizes the element. This should only be called by the
+	// element's parent.
+	Resize (width, height int)
+
+	// SetParentHooks gives the element callbacks that let it send
+	// information to its parent element without it knowing anything about
+	// the parent element or containing any reference to it. When a parent
+	// element adopts a child element, it must set these callbacks.
+	SetParentHooks (callbacks ParentHooks)
+}
+
+// SelectionDirection represents a keyboard navigation direction.
+type SelectionDirection int
+
+const (
+	SelectionDirectionNeutral  SelectionDirection =  0
+	SelectionDirectionBackward SelectionDirection = -1
+	SelectionDirectionForward  SelectionDirection =  1
+)
+
+// Canon returns a well-formed direction.
+func (direction SelectionDirection) Canon () (canon SelectionDirection) {
+	if direction > 0 {
+		return SelectionDirectionForward
+	} else if direction == 0 {
+		return SelectionDirectionNeutral
+	} else {
+		return SelectionDirectionBackward
+	}
+}
+
+// Selectable represents an element that has keyboard navigation support. This
+// includes inputs, buttons, sliders, etc. as well as any elements that have
+// children (so keyboard navigation events can be propagated downward).
+type Selectable interface {
+	Element
+
+	// Selected returns whether or not this element is currently selected.
+	Selected () (selected bool)
+
+	// Select selects this element, if its parent element grants the
+	// request.
+	Select ()
+
+	// HandleSelection causes this element to mark itself as selected, if it
+	// can currently be. Otherwise, it will return false and do nothing.
+	HandleSelection (direction SelectionDirection) (accepted bool)
+
+	// HandleDeselection causes this element to mark itself and all of its
+	// children as deselected.
+	HandleDeselection ()
+}
+
+// KeyboardTarget represents an element that can receive keyboard input.
+type KeyboardTarget interface {
+	Element
+
+	// HandleKeyDown is called when a key is pressed down while this element
+	// has keyboard focus. It is important to note that not every key down
+	// event is guaranteed to be paired with exactly one key up event. This
+	// is the reason a list of modifier keys held down at the time of the
+	// key press is given.
+	HandleKeyDown (key Key, modifiers Modifiers, repeated bool)
+
+	// HandleKeyUp is called when a key is released while this element has
+	// keyboard focus.
+	HandleKeyUp (key Key, modifiers Modifiers)
+}
+
+// MouseTarget represents an element that can receive mouse events.
+type MouseTarget interface {
+	Element
+
+	// Each of these handler methods is passed the position of the mouse
+	// cursor at the time of the event as x, y.
+
+	// HandleMouseDown is called when a mouse button is pressed down on this
+	// element.
+	HandleMouseDown (x, y int, button Button)
+
+	// HandleMouseUp is called when a mouse button is released that was
+	// originally pressed down on this element.
+	HandleMouseUp (x, y int, button Button)
+
+	// HandleMouseMove is called when the mouse is moved over this element,
+	// or the mouse is moving while being held down and originally pressed
+	// down on this element.
+	HandleMouseMove (x, y int)
+
+	// HandleScroll is called when the mouse is scrolled. The X and Y
+	// direction of the scroll event are passed as deltaX and deltaY.
+	HandleScroll (x, y int, deltaX, deltaY float64)
+}
+
+// Expanding represents an element who's preferred minimum height can change in
+// response to its width.
+type Expanding interface {
+	Element
+
+	// HeightForWidth returns what the element's minimum height would be if
+	// resized to a specified width. This does not actually alter the state
+	// of the element in any way, but it may perform significant work, so it
+	// should be called sparingly.
+	//
+	// It is reccomended that parent containers check for this interface and
+	// take this method's value into account in order to support things like
+	// flow layouts and text wrapping, but it is not absolutely necessary.
+	// The element's MinimumSize method will still return the absolute
+	// minimum size that the element may be resized to.
+	//
+	// It is important to note that if a parent container checks for
+	// expanding chilren, it itself will likely need to be expanding.
+	MinimumHeightFor (width int) (height int)
+}

elements/basic/button.go

@@ -13,6 +13,7 @@ type Button struct {
 	
 	pressed  bool
 	enabled  bool
+	selected bool
 	onClick func ()
 
 	text   string
@@ -24,89 +25,103 @@ func NewButton (text string) (element *Button) {
 	element = &Button { enabled: true }
 	element.Core, element.core = core.NewCore(element)
 	element.drawer.SetFace(theme.FontFaceRegular())
-	element.core.SetSelectable(true)
 	element.SetText(text)
 	return
 }
 
-// Handle handles an event.
+func (element *Button) Resize (width, height int) {
-func (element *Button) Handle (event tomo.Event) {
+	element.core.AllocateCanvas(width, height)
-	switch event.(type) {
+	element.draw()
-	case tomo.EventResize:
+}
-		resizeEvent := event.(tomo.EventResize)
+
-		element.core.AllocateCanvas (
+func (element *Button) HandleMouseDown (x, y int, button tomo.Button) {
-			resizeEvent.Width,
+	element.Select()
-			resizeEvent.Height)
+	if button != tomo.ButtonLeft { return }
+	element.pressed = true
+	if element.core.HasImage() {
 		element.draw()
+		element.core.PushAll()
+	}
+}
 
-	case tomo.EventMouseDown:
+func (element *Button) HandleMouseUp (x, y int, button tomo.Button) {
-		if !element.enabled { break }
+	if button != tomo.ButtonLeft { return }
+	element.pressed = false
+	if element.core.HasImage() {
+		element.draw()
+		element.core.PushAll()
+	}
 
-		mouseDownEvent := event.(tomo.EventMouseDown)
+	within := image.Point { x, y }.
-		element.Select()
+		In(element.Bounds())
-		if mouseDownEvent.Button != tomo.ButtonLeft { break }
+		
+	if within && element.onClick != nil {
+		element.onClick()
+	}
+}
+
+func (element *Button) HandleMouseMove (x, y int) { }
+func (element *Button) HandleScroll (x, y int, deltaX, deltaY float64) { }
+
+func (element *Button) HandleKeyDown (
+	key tomo.Key,
+	modifiers tomo.Modifiers,
+	repeated bool,
+) {
+	if key == tomo.KeyEnter {
 		element.pressed = true
 		if element.core.HasImage() {
 			element.draw()
 			element.core.PushAll()
 		}
+	}
+}
 
-	case tomo.EventKeyDown:
+func (element *Button) HandleKeyUp(key tomo.Key, modifiers tomo.Modifiers) {
-		keyDownEvent := event.(tomo.EventKeyDown)
+	if key == tomo.KeyEnter && element.pressed {
-		if keyDownEvent.Key == tomo.KeyEnter {
-			element.pressed = true
-			if element.core.HasImage() {
-				element.draw()
-				element.core.PushAll()
-			}
-		}
-
-	case tomo.EventMouseUp:
-		if !element.enabled { break }
-	
-		mouseUpEvent := event.(tomo.EventMouseUp)
-		if mouseUpEvent.Button != tomo.ButtonLeft { break }
 		element.pressed = false
 		if element.core.HasImage() {
 			element.draw()
 			element.core.PushAll()
 		}
-
+		if element.onClick != nil {
-		within := image.Point { mouseUpEvent.X, mouseUpEvent.Y }.
-			In(element.Bounds())
-			
-		if within && element.onClick != nil {
 			element.onClick()
 		}
-
-	case tomo.EventKeyUp:
-		keyDownEvent := event.(tomo.EventKeyUp)
-		if keyDownEvent.Key == tomo.KeyEnter && element.pressed {
-			element.pressed = false
-			if element.core.HasImage() {
-				element.draw()
-				element.core.PushAll()
-			}
-			if element.onClick != nil {
-				element.onClick()
-			}
-		}
-
-	case tomo.EventSelect:
-		element.core.SetSelected(true)
-		if element.core.HasImage() {
-			element.draw()
-			element.core.PushAll()
-		}
-
-	case tomo.EventDeselect:
-		element.core.SetSelected(false)
-		if element.core.HasImage() {
-			element.draw()
-			element.core.PushAll()
-		}
 	}
-	return
+}
+
+func (element *Button) Selected () (selected bool) {
+	return element.selected
+}
+
+func (element *Button) Select () {
+	element.core.RequestSelection()
+}
+
+func (element *Button) HandleSelection (
+	direction tomo.SelectionDirection,
+) (
+	accepted bool,
+) {
+	if !element.enabled { return false }
+	if element.selected && direction != tomo.SelectionDirectionNeutral {
+		return false
+	}
+	
+	element.selected = true
+	if element.core.HasImage() {
+		element.draw()
+		element.core.PushAll()
+	}
+	return true
+}
+
+func (element *Button) HandleDeselection () {
+	element.selected = false
+	if element.core.HasImage() {
+		element.draw()
+		element.core.PushAll()
+	}
 }
 
 // OnClick sets the function to be called when the button is clicked.
@@ -114,17 +129,10 @@ func (element *Button) OnClick (callback func ()) {
 	element.onClick = callback
 }
 
-// Select requests that this button's parent container send it a selection
-// event.
-func (element *Button) Select () {
-	element.core.Select()
-}
-
 // SetEnabled sets whether this button can be clicked or not.
 func (element *Button) SetEnabled (enabled bool) {
 	if element.enabled == enabled { return }
 	element.enabled = enabled
-	element.core.SetSelectable(enabled)
 	if element.core.HasImage () {
 		element.draw()
 		element.core.PushAll()

elements/basic/container.go

@@ -12,10 +12,12 @@ type Container struct {
 	*core.Core
 	core core.CoreControl
 
-	layout   tomo.Layout
+	layout     tomo.Layout
-	children []tomo.LayoutEntry
+	children   []tomo.LayoutEntry
-	drags    [10]tomo.Element
+	drags      [10]tomo.MouseTarget
-	warping  bool
+	warping    bool
+	selected   bool
+	selectable bool
 }
 
 // NewContainer creates a new container.
@@ -44,18 +46,10 @@ func (element *Container) Adopt (child tomo.Element, expand bool) {
 		MinimumSizeChange: func (int, int) {
 			element.updateMinimumSize()
 		},
-		SelectabilityChange: func (bool) {
-			element.updateSelectable()
-		},
 		SelectionRequest: func () (granted bool) {
-			if !child.Selectable() { return }
+			child, selectable := child.(tomo.Selectable)
-			if element.core.Select() {
+			if !selectable { return }
-				element.propogateToSelected(tomo.EventDeselect { })
+			return element.childSelectionRequestCallback(child)
-				child.Handle(tomo.EventSelect { })
-				return true
-			}
-			
-			return
 		},
 		Draw: func (region tomo.Canvas) {
 			element.drawChildRegion(child, region)
@@ -176,122 +170,168 @@ func (element *Container) childPosition (child tomo.Element) (position image.Poi
 	return
 }
 
-func (element *Container) Handle (event tomo.Event) {
+func (element *Container) Resize (width, height int) {
-	switch event.(type) {
+	element.core.AllocateCanvas(width, height)
-	case tomo.EventResize:
+	element.recalculate()
-		resizeEvent := event.(tomo.EventResize)
+	element.draw()
-		element.core.AllocateCanvas (
-			resizeEvent.Width,
-			resizeEvent.Height)
-		element.recalculate()
-		element.draw()
-
-	case tomo.EventMouseDown:
-		mouseDownEvent := event.(tomo.EventMouseDown)
-		child := element.ChildAt (image.Pt (
-			mouseDownEvent.X,
-			mouseDownEvent.Y))
-		if child == nil { break }
-		element.drags[mouseDownEvent.Button] = child
-		childPosition := element.childPosition(child)
-		child.Handle (tomo.EventMouseDown {
-			Button: mouseDownEvent.Button,
-			X: mouseDownEvent.X - childPosition.X,
-			Y: mouseDownEvent.Y - childPosition.Y,
-		})
-
-	case tomo.EventMouseUp:
-		mouseUpEvent := event.(tomo.EventMouseUp)
-		child := element.drags[mouseUpEvent.Button]
-		if child == nil { break }
-		element.drags[mouseUpEvent.Button] = nil
-		childPosition := element.childPosition(child)
-		child.Handle (tomo.EventMouseUp {
-			Button: mouseUpEvent.Button,
-			X: mouseUpEvent.X - childPosition.X,
-			Y: mouseUpEvent.Y - childPosition.Y,
-		})
-
-	case tomo.EventMouseMove:
-		mouseMoveEvent := event.(tomo.EventMouseMove)
-		for _, child := range element.drags {
-			if child == nil { continue }
-			childPosition := element.childPosition(child)
-			child.Handle (tomo.EventMouseMove {
-				X: mouseMoveEvent.X - childPosition.X,
-				Y: mouseMoveEvent.Y - childPosition.Y,
-			})
-		}
-
-	case tomo.EventSelect:
-		if !element.Selectable() { break }
-		element.core.SetSelected(true)
-		
-		// select the first selectable element
-		for _, entry := range element.children {
-			if entry.Selectable() {
-				entry.Handle(event)
-				break
-			}
-		}
-
-	case tomo.EventDeselect:
-		element.core.SetSelected(false)
-		element.propogateToSelected(event)
-
-	default:
-		// other events are just directly sent to the selected child.
-		element.propogateToSelected(event)
-	}
-	return
 }
 
-func (element *Container) propogateToSelected (event tomo.Event) {
+// TODO: implement KeyboardTarget
-	for _, entry := range element.children {
+
-		if entry.Selected() {
+func (element *Container) HandleMouseDown (x, y int, button tomo.Button) {
-			entry.Handle(event)
+	child, handlesMouse := element.ChildAt(image.Pt(x, y)).(tomo.MouseTarget)
-		}
+	if !handlesMouse { return }
+	element.drags[button] = child
+	childPosition := element.childPosition(child)
+	child.HandleMouseDown(x - childPosition.X, y - childPosition.Y, button)
+}
+
+func (element *Container) HandleMouseUp (x, y int, button tomo.Button) {
+	child := element.drags[button]
+	if child == nil { return }
+	element.drags[button] = nil
+	childPosition := element.childPosition(child)
+	child.HandleMouseUp(x - childPosition.X, y - childPosition.Y, button)
+}
+
+func (element *Container) HandleMouseMove (x, y int) {
+	for _, child := range element.drags {
+		if child == nil { continue }
+		childPosition := element.childPosition(child)
+		child.HandleMouseMove(x - childPosition.X, y - childPosition.Y)
 	}
 }
 
-func (element *Container) AdvanceSelection (direction int) (ok bool) {
+func (element *Container) HandleScroll (x, y int, deltaX, deltaY float64) {
-	if !element.Selectable() { return }
+	child, handlesMouse := element.ChildAt(image.Pt(x, y)).(tomo.MouseTarget)
+	if !handlesMouse { return }
+	childPosition := element.childPosition(child)
+	child.HandleScroll(x - childPosition.X, y - childPosition.Y, deltaX, deltaY)
+}
+
+func (element *Container) HandleKeyDown (
+	key tomo.Key,
+	modifiers tomo.Modifiers,
+	repeated bool,
+) {
+	element.forSelected (func (child tomo.Selectable) bool {
+		child0, handlesKeyboard := child.(tomo.KeyboardTarget)
+		if handlesKeyboard {
+			child0.HandleKeyDown(key, modifiers, repeated)
+		}
+		return true
+	})
+}
+
+func (element *Container) HandleKeyUp(key tomo.Key, modifiers tomo.Modifiers) {
+	element.forSelected (func (child tomo.Selectable) bool {
+		child0, handlesKeyboard := child.(tomo.KeyboardTarget)
+		if handlesKeyboard {
+			child0.HandleKeyUp(key, modifiers)
+		}
+		return true
+	})
+}
+
+func (element *Container) Selected () (selected bool) {
+	return element.selected
+}
+
+func (element *Container) Select () {
+	element.core.RequestSelection()
+}
+
+func (element *Container) HandleSelection (direction tomo.SelectionDirection) (ok bool) {
+	if !element.selectable { return false }
+	direction = direction.Canon()
 
 	firstSelected := element.firstSelected()
 	if firstSelected < 0 {
-		for _, entry := range element.children {
+		found := false
-			if entry.Selectable() {
+		switch direction {
-				entry.Handle(tomo.EventSelect { })
+		case tomo.SelectionDirectionBackward:
+			element.forSelectableBackward (func (child tomo.Selectable) bool {
+				if child.HandleSelection(direction) {
+					element.selected = true
+					found = true
+					return false
+				}
+				return true
+			})
+			return true
+		
+		case tomo.SelectionDirectionNeutral, tomo.SelectionDirectionForward:
+			element.forSelectable (func (child tomo.Selectable) bool {
+				if child.HandleSelection(direction) {
+					element.selected = true
+					found = true
+					return false
+				}
+				return true
+			})
+		}
+		return found
+	} else {
+		firstSelectedChild :=
+			element.children[firstSelected].Element.(tomo.Selectable)
+		
+		for index := firstSelected + int(direction);
+			index < len(element.children) && index >= 0;
+			index += int(direction) {
+
+			child, selectable :=
+				element.children[index].
+				Element.(tomo.Selectable)
+			if selectable && child.HandleSelection(direction) {
+				firstSelectedChild.HandleDeselection()
+				element.selected = true
 				return true
 			}
 		}
-	} else {
-		nextSelectable := -1
-		step := 1
-		if direction < 0 { step = - 1 }
-		for index := firstSelected + step;
-			index < len(element.children) && index > 0;
-			index += step {
-
-			if element.children[index].Selectable() {
-				nextSelectable = index
-				break
-			}
-		}
-
-		if nextSelectable > 0 {
-			element.children[firstSelected ].Handle(tomo.EventDeselect { })
-			element.children[nextSelectable].Handle(tomo.EventSelect   { })
-			return true
-		}
 	}
 	
-	return
+	return false
+}
+
+func (element *Container) HandleDeselection () {
+	element.selected = false
+	element.forSelected (func (child tomo.Selectable) bool {
+		child.HandleDeselection()
+		return true
+	})
+}
+
+func (element *Container) forSelected (callback func (child tomo.Selectable) bool) {
+	for _, entry := range element.children {
+		child, selectable := entry.Element.(tomo.Selectable)
+		if selectable && child.Selected() {
+			if !callback(child) { break }
+		}
+	}
+}
+
+func (element *Container) forSelectable (callback func (child tomo.Selectable) bool) {
+	for _, entry := range element.children {
+		child, selectable := entry.Element.(tomo.Selectable)
+		if selectable {
+			if !callback(child) { break }
+		}
+	}
+}
+
+func (element *Container) forSelectableBackward (callback func (child tomo.Selectable) bool) {
+	for index := len(element.children) - 1; index >= 0; index -- {
+		child, selectable := element.children[index].Element.(tomo.Selectable)
+		if selectable {
+			if !callback(child) { break }
+		}
+	}
 }
 
 func (element *Container) firstSelected () (index int) {
 	for currentIndex, entry := range element.children {
-		if entry.Selected() {
+		child, selectable := entry.Element.(tomo.Selectable)
+		if selectable && child.Selected() {
 			return currentIndex
 		}
 	}
@@ -299,15 +339,36 @@ func (element *Container) firstSelected () (index int) {
 }
 
 func (element *Container) updateSelectable () {
-	selectable := false
+	element.selectable = false
-	for _, entry := range element.children {
+	element.forSelectable (func (tomo.Selectable) bool {
-		if entry.Selectable() { selectable = true }
+		element.selectable = true
+		return false
+	})
+	if !element.selectable {
+		element.selected = false
+	}
+}
+
+func (element *Container) childSelectionRequestCallback (
+	child tomo.Selectable,
+) (
+	granted bool,
+) {
+	if element.core.RequestSelection() {
+		element.forSelected (func (child tomo.Selectable) bool {
+			child.HandleDeselection()
+			return true
+		})
+		child.HandleSelection(tomo.SelectionDirectionNeutral)
+		return true
+	} else {
+		return false
 	}
-	element.core.SetSelectable(selectable)
 }
 
 func (element *Container) updateMinimumSize () {
-	element.core.SetMinimumSize(element.layout.MinimumSize(element.children))
+	element.core.SetMinimumSize (
+		element.layout.MinimumSize(element.children, 1e9))
 }
 
 func (element *Container) recalculate () {

elements/basic/label.go

@@ -1,7 +1,6 @@
 package basic
 
 import "image"
-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"
@@ -28,20 +27,13 @@ func NewLabel (text string, wrap bool) (element *Label) {
 	return
 }
 
-// Handle handles and event.
+func (element *Label) Resize (width, height int) {
-func (element *Label) Handle (event tomo.Event) {
+	element.core.AllocateCanvas(width, height)
-	switch event.(type) {
+	if element.wrap {
-	case tomo.EventResize:
+		element.drawer.SetMaxWidth(width)
-		resizeEvent := event.(tomo.EventResize)
+		element.drawer.SetMaxHeight(height)
-		element.core.AllocateCanvas (
-			resizeEvent.Width,
-			resizeEvent.Height)
-		if element.wrap {
-			element.drawer.SetMaxWidth (resizeEvent.Width)
-			element.drawer.SetMaxHeight(resizeEvent.Height)
-		}
-		element.draw()
 	}
+	element.draw()
 	return
 }
 

elements/core/core.go

@@ -27,89 +27,87 @@ func NewCore (parent tomo.Element) (core *Core, control CoreControl) {
 	return
 }
 
-func (core Core) ColorModel () (model color.Model) {
+// ColorModel fulfills the draw.Image interface.
+func (core *Core) ColorModel () (model color.Model) {
 	return color.RGBAModel
 }
 
-func (core Core) At (x, y int) (pixel color.Color) {
+// ColorModel fulfills the draw.Image interface.
+func (core *Core) At (x, y int) (pixel color.Color) {
 	return core.canvas.At(x, y)
 }
 
-func (core Core) Bounds () (bounds image.Rectangle) {
+// ColorModel fulfills the draw.Image interface.
+func (core *Core) Bounds () (bounds image.Rectangle) {
 	return core.canvas.Bounds()
 }
 
-func (core Core) Set (x, y int, c color.Color) () {
+// ColorModel fulfills the draw.Image interface.
+func (core *Core) Set (x, y int, c color.Color) () {
 	core.canvas.Set(x, y, c)
 }
 
-func (core Core) Buffer () (data []color.RGBA, stride int) {
+// Buffer fulfills the tomo.Canvas interface.
+func (core *Core) Buffer () (data []color.RGBA, stride int) {
 	return core.canvas.Buffer()
 }
 
-func (core Core) Selectable () (selectable bool) {
+// MinimumSize fulfils the tomo.Element interface. This should not need to be
-	return core.selectable
+// overridden.
-}
+func (core *Core) MinimumSize () (width, height int) {
-
+	return core.metrics.minimumWidth, core.metrics.minimumHeight
-func (core Core) Selected () (selected bool) {
-	return core.selected
-}
-
-func (core Core) AdvanceSelection (direction int) (ok bool) {
-	return
 }
 
+// SetParentHooks fulfils the tomo.Element interface. This should not need to be
+// overridden.
 func (core *Core) SetParentHooks (hooks tomo.ParentHooks) {
 	core.hooks = hooks
 }
 
-func (core Core) MinimumSize () (width, height int) {
+// CoreControl is a struct that can exert control over a Core struct. It can be
-	return core.metrics.minimumWidth, core.metrics.minimumHeight
+// used as a canvas. It must not be directly embedded into an element, but
-}
+// instead kept as a private member. When a Core struct is created, a
-
+// corresponding CoreControl struct is linked to it and returned alongside it.
-// CoreControl is a struct that can exert control over a control struct. It can
-// be used as a canvas. It must not be directly embedded into an element, but
-// instead kept as a private member.
 type CoreControl struct {
 	tomo.BasicCanvas
 	core *Core
 }
 
-func (control CoreControl) HasImage () (empty bool) {
+// RequestSelection requests that the element's parent send it a selection
-	return !control.Bounds().Empty()
+// event. If the request was granted, it returns true. If it was denied, it
-}
+// returns false.
-
+func (control CoreControl) RequestSelection () (granted bool) {
-func (control CoreControl) Select () (granted bool) {
 	return control.core.hooks.RunSelectionRequest()
 }
 
-func (control CoreControl) SetSelected (selected bool) {
+// HasImage returns true if the core has an allocated image buffer, and false if
-	if !control.core.selectable { return }
+// it doesn't.
-	control.core.selected = selected
+func (control CoreControl) HasImage () (has bool) {
-}
+	return !control.Bounds().Empty()
-
-func (control CoreControl) SetSelectable (selectable bool) {
-	if control.core.selectable == selectable { return }
-	control.core.selectable = selectable
-	if !selectable { control.core.selected = false }
-	control.core.hooks.RunSelectabilityChange(selectable)
 }
 
+// PushRegion pushes the selected region of pixels to the parent element. This
+// does not need to be called when responding to a resize event.
 func (control CoreControl) PushRegion (bounds image.Rectangle) {
 	control.core.hooks.RunDraw(tomo.Cut(control, bounds))
 }
 
+// PushAll pushes all pixels to the parent element. This does not need to be
+// called when responding to a resize event.
 func (control CoreControl) PushAll () {
 	control.PushRegion(control.Bounds())
 }
 
+// AllocateCanvas resizes the canvas, constraining the width and height so that
+// they are not less than the specified minimum width and height.
 func (control *CoreControl) AllocateCanvas (width, height int) {
-	core := control.core
 	width, height, _ = control.ConstrainSize(width, height)
-	core.canvas  = tomo.NewBasicCanvas(width, height)
+	control.core.canvas = tomo.NewBasicCanvas(width, height)
-	control.BasicCanvas = core.canvas
+	control.BasicCanvas = control.core.canvas
 }
 
+// SetMinimumSize sets the minimum size of this element, notifying the parent
+// element in the process.
 func (control CoreControl) SetMinimumSize (width, height int) {
 	core := control.core
 	if width == core.metrics.minimumWidth &&
@@ -123,20 +121,19 @@ func (control CoreControl) SetMinimumSize (width, height int) {
 
 	// if there is an image buffer, and the current size is less
 	// than this new minimum size, send core.parent a resize event.
-	bounds := control.Bounds()
+	if control.HasImage() {
-	imageWidth,
+		bounds := control.Bounds()
-	imageHeight,
+		imageWidth,
-	constrained := control.ConstrainSize (
+		imageHeight,
-		bounds.Dx(),
+		constrained := control.ConstrainSize(bounds.Dx(), bounds.Dy())
-		bounds.Dy())
+		if constrained {
-	if constrained {
+			core.parent.Resize(imageWidth, imageHeight)
-		core.parent.Handle (tomo.EventResize {
+		}
-			Width:  imageWidth,
-			Height: imageHeight,
-		})
 	}
 }
 
+// ConstrainSize contstrains the specified width and height to the minimum width
+// and height, and returns wether or not anything ended up being constrained.
 func (control CoreControl) ConstrainSize (
 	inWidth, inHeight int,
 ) (

elements/fun/clock.go

@@ -3,7 +3,6 @@ package fun
 import "time"
 import "math"
 import "image"
-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"
@@ -21,15 +20,9 @@ func NewAnalogClock (newTime time.Time) (element *AnalogClock) {
 	return
 }
 
-func (element *AnalogClock) Handle (event tomo.Event) {
+func (element *AnalogClock) Resize (width, height int) {
-	switch event.(type) {
+	element.core.AllocateCanvas(width, height)
-	case tomo.EventResize:
+	element.draw()
-		resizeEvent := event.(tomo.EventResize)
-		element.core.AllocateCanvas (
-			resizeEvent.Width,
-			resizeEvent.Height)
-		element.draw()
-	}
 }
 
 func (element *AnalogClock) SetTime (newTime time.Time) {

elements/testing/mouse.go

@@ -26,58 +26,47 @@ func NewMouse () (element *Mouse) {
 	return
 }
 
-func (element *Mouse) Handle (event tomo.Event) {
+func (element *Mouse) Resize (width, height int) {
-	switch event.(type) {
+	element.core.AllocateCanvas(width, height)
-	case tomo.EventResize:
+	artist.FillRectangle (
-		resizeEvent := event.(tomo.EventResize)
+		element.core,
-		element.core.AllocateCanvas (
+		theme.AccentPattern(),
-			resizeEvent.Width,
+		element.Bounds())
-			resizeEvent.Height)
+	artist.StrokeRectangle (
-		artist.FillRectangle (
+		element.core,
-			element.core,
+		artist.NewUniform(color.Black), 1,
-			theme.AccentPattern(),
+		element.Bounds())
-			element.Bounds())
+	artist.Line (
-		artist.StrokeRectangle (
+		element.core, artist.NewUniform(color.White), 3,
-			element.core,
+		image.Pt(1, 1),
-			artist.NewUniform(color.Black), 1,
+		image.Pt(width - 2, height - 2))
-			element.Bounds())
+	artist.Line (
-		artist.Line (
+		element.core, artist.NewUniform(color.White), 1,
-			element.core, artist.NewUniform(color.White), 3,
+		image.Pt(1, height - 2),
-			image.Pt(1, 1),
+		image.Pt(width - 2, 1))
-			image.Pt(resizeEvent.Width - 2, resizeEvent.Height - 2))
-		artist.Line (
-			element.core, artist.NewUniform(color.White), 1,
-			image.Pt(1, resizeEvent.Height - 2),
-			image.Pt(resizeEvent.Width - 2, 1))
-	
-	case tomo.EventMouseDown:
-		element.drawing = true
-		mouseDownEvent := event.(tomo.EventMouseDown)
-		element.lastMousePos = image.Pt (
-			mouseDownEvent.X,
-			mouseDownEvent.Y)
-
-	case tomo.EventMouseUp:
-		element.drawing = false
-		mouseUpEvent := event.(tomo.EventMouseUp)
-		mousePos := image.Pt (
-			mouseUpEvent.X,
-			mouseUpEvent.Y)
-		element.core.PushRegion (artist.Line (
-			element.core, element.color, 1,
-			element.lastMousePos, mousePos))
-		element.lastMousePos = mousePos
-
-	case tomo.EventMouseMove:
-		if !element.drawing { return }
-		mouseMoveEvent := event.(tomo.EventMouseMove)
-		mousePos := image.Pt (
-			mouseMoveEvent.X,
-			mouseMoveEvent.Y)
-		element.core.PushRegion (artist.Line (
-			element.core, element.color, 1,
-			element.lastMousePos, mousePos))
-		element.lastMousePos = mousePos
-	}
-	return
 }
+
+func (element *Mouse) HandleMouseDown (x, y int, button tomo.Button) {
+	element.drawing = true
+	element.lastMousePos = image.Pt(x, y)
+}
+
+func (element *Mouse) HandleMouseUp (x, y int, button tomo.Button) {
+	element.drawing = false
+	mousePos := image.Pt(x, y)
+	element.core.PushRegion (artist.Line (
+		element.core, element.color, 1,
+		element.lastMousePos, mousePos))
+	element.lastMousePos = mousePos
+}
+
+func (element *Mouse) HandleMouseMove (x, y int) {
+	if !element.drawing { return }
+	mousePos := image.Pt(x, y)
+	element.core.PushRegion (artist.Line (
+		element.core, element.color, 1,
+		element.lastMousePos, mousePos))
+	element.lastMousePos = mousePos
+}
+
+func (element *Mouse) HandleScroll (x, y int, deltaX, deltaY float64) { }

event.go

@@ -1,88 +0,0 @@
-package tomo
-
-// Event represents any event. Use a type switch to figure out what sort of
-// event it is.
-type Event interface { }
-
-// EventResize is sent to an element when its parent decides to resize it.
-// Elements should not do anything if the width and height do not change.
-type EventResize struct {
-	// The width and height the element should not be less than the
-	// element's reported minimum width and height. If by some chance they
-	// are anyways, the element should use its minimum width and height
-	// instead.
-	Width, Height int
-}
-
-// EventKeyDown is sent to the currently selected element when a key on the
-// keyboard is pressed. Containers must propagate this event downwards.
-type EventKeyDown struct {
-	Key
-	Modifiers
-	Repeated bool
-}
-
-// EventKeyDown is sent to the currently selected element when a key on the
-// keyboard is released. Containers must propagate this event downwards.
-type EventKeyUp struct {
-	Key
-	Modifiers
-}
-
-// EventMouseDown is sent to the element the mouse is positioned over when it is
-// clicked. Containers must propagate this event downwards, with X and Y values
-// relative to the top left corner of the child element.
-type EventMouseDown struct {
-	// The button that was released
-	Button
-	
-	// The X and Y position of the mouse cursor at the time of the event,
-	// relative to the top left corner of the element
-	X, Y int
-}
-
-// EventMouseUp is sent to the element that was positioned under the mouse the
-// last time this particular mouse button was pressed down when it is released.
-// Containers must propagate this event downwards, with X and Y values relative
-// to the top left corner of the child element.
-type EventMouseUp struct {
-	// The button that was released
-	Button
-	
-	// The X and Y position of the mouse cursor at the time of the event,
-	// relative to the top left corner of the element
-	X, Y int
-}
-
-// EventMouseMove is sent to the element positioned under the mouse cursor when
-// the mouse moves, or if a mouse button is currently being pressed, the element
-// that the mouse was positioned under when it was pressed down. Containers must
-// propogate this event downwards, with X and Y values relative to the top left
-// corner of the child element.
-type EventMouseMove struct {
-	// The X and Y position of the mouse cursor at the time of the event,
-	// relative to the top left corner of the element
-	X, Y int
-}
-
-// EventScroll is sent to the element positioned under the mouse cursor when the
-// scroll wheel (or equivalent) is spun. Containers must propogate this event
-// downwards.
-type EventScroll struct {
-	// The X and Y position of the mouse cursor at the time of the event,
-	// relative to the top left corner of the element
-	X, Y int
-
-	// The X and Y amount the scroll wheel moved
-	ScrollX, ScrollY int
-}
-
-// EventSelect is sent to selectable elements when they become selected, whether
-// by a mouse click or by keyboard navigation. Containers must propagate this
-// event downwards.
-type EventSelect struct { }
-
-// EventDeselect is sent to selectable elements when they stop being selected,
-// whether by a mouse click or by keyboard navigation. Containers must propagate
-// this event downwards.
-type EventDeselect struct { }

examples/dialogLayout/main.go

@@ -1,8 +1,8 @@
 package main
 
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

examples/flow/main.go

@@ -2,8 +2,8 @@ package main
 
 import "git.tebibyte.media/sashakoshka/tomo"
 import "git.tebibyte.media/sashakoshka/tomo/flow"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

examples/goroutines/main.go

@@ -3,9 +3,9 @@ package main
 import "os"
 import "time"
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/fun"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

examples/horizontalLayout/main.go

@@ -1,9 +1,9 @@
 package main
 
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
 import "git.tebibyte.media/sashakoshka/tomo/elements/testing"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

examples/popups/main.go

@@ -2,8 +2,8 @@ package main
 
 import "git.tebibyte.media/sashakoshka/tomo"
 import "git.tebibyte.media/sashakoshka/tomo/popups"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

examples/verticalLayout/main.go

@@ -1,9 +1,9 @@
 package main
 
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
 import "git.tebibyte.media/sashakoshka/tomo/elements/testing"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 import _ "git.tebibyte.media/sashakoshka/tomo/backends/x"
 
 func main () {

layout.go

@@ -0,0 +1,27 @@
+package tomo
+
+import "image"
+
+// LayoutEntry associates an element with layout and positioning information so
+// it can be arranged by a Layout.
+type LayoutEntry struct {
+	Element
+	Position image.Point
+	Expand bool
+}
+
+// Layout is capable of arranging elements within a container. It is also able
+// to determine the minimum amount of room it needs to do so.
+type Layout interface {
+	// Arrange takes in a slice of entries and a bounding width and height,
+	// and changes the position of the entiries in the slice so that they
+	// are properly laid out. The given width and height should not be less
+	// than what is returned by MinimumSize.
+	Arrange (entries []LayoutEntry, width, height int)
+
+	// MinimumSize returns the minimum width and height that the layout
+	// needs to properly arrange the given slice of layout entries, given a
+	// "suqeeze" width so that the height can be determined for elements
+	// fulfilling the Expanding interface.
+	MinimumSize (entries []LayoutEntry, squeeze int) (width, height int)
+}

layouts/dialog.go

@@ -4,6 +4,11 @@ import "image"
 import "git.tebibyte.media/sashakoshka/tomo"
 import "git.tebibyte.media/sashakoshka/tomo/theme"
 
+// Dialog arranges elements in the form of a dialog box. The first element is
+// positioned above as the main focus of the dialog, and is set to expand
+// regardless of whether it is expanding or not. The remaining elements are
+// arranged at the bottom in a row called the control row, which is aligned to
+// the right, the last element being the rightmost one.
 type Dialog struct {
 	// If Gap is true, a gap will be placed between each element.
 	Gap bool
@@ -39,10 +44,7 @@ func (layout Dialog) Arrange (entries []tomo.LayoutEntry, width, height int) {
 		mainBounds := entries[0].Bounds()
 		if mainBounds.Dy() != mainHeight ||
 			mainBounds.Dx() != width {
-			entries[0].Handle (tomo.EventResize {
+			entries[0].Resize(width, mainHeight)
-				Width:  width,
-				Height: mainHeight,
-			})
 		}
 	}
 
@@ -94,10 +96,7 @@ func (layout Dialog) Arrange (entries []tomo.LayoutEntry, width, height int) {
 			entryBounds := entry.Bounds()
 			if entryBounds.Dy() != controlRowHeight ||
 				entryBounds.Dx() != entryWidth {
-				entry.Handle (tomo.EventResize {
+				entry.Resize(entryWidth, controlRowHeight)
-					Width:  entryWidth,
-					Height: controlRowHeight,
-				})
 			}
 		}
 	}
@@ -107,7 +106,12 @@ func (layout Dialog) Arrange (entries []tomo.LayoutEntry, width, height int) {
 
 // MinimumSize returns the minimum width and height that will be needed to
 // arrange the given list of entries.
-func (layout Dialog) MinimumSize (entries []tomo.LayoutEntry) (width, height int) {
+func (layout Dialog) MinimumSize (
+	entries []tomo.LayoutEntry,
+	squeeze int,
+) (
+	width, height int,
+) {
 	if len(entries) > 0 {
 		mainChildHeight := 0
 		width, mainChildHeight = entries[0].MinimumSize()

layouts/horizontal.go

@@ -63,17 +63,19 @@ func (layout Horizontal) Arrange (entries []tomo.LayoutEntry, width, height int)
 		x += entryWidth
 		entryBounds := entry.Bounds()
 		if entryBounds.Dy() != height || entryBounds.Dx() != entryWidth {
-			entry.Handle (tomo.EventResize {
+			entry.Resize(entryWidth, height)
-				Width:  entryWidth,
-				Height: height,
-			})
 		}
 	}
 }
 
 // MinimumSize returns the minimum width and height that will be needed to
 // arrange the given list of entries.
-func (layout Horizontal) MinimumSize (entries []tomo.LayoutEntry) (width, height int) {
+func (layout Horizontal) MinimumSize (
+	entries []tomo.LayoutEntry,
+	squeeze int,
+) (
+	width, height int,
+) {
 	for index, entry := range entries {
 		entryWidth, entryHeight := entry.MinimumSize()
 		if entryHeight > height {

layouts/vertical.go

@@ -63,18 +63,19 @@ func (layout Vertical) Arrange (entries []tomo.LayoutEntry, width, height int) {
 		y += entryHeight
 		entryBounds := entry.Bounds()
 		if entryBounds.Dx() != width || entryBounds.Dy() != entryHeight {
-			// println(entryHeight)
+			entry.Resize(width, entryHeight)
-			entry.Handle (tomo.EventResize {
-				Width:  width,
-				Height: entryHeight,
-			})
 		}
 	}
 }
 
 // MinimumSize returns the minimum width and height that will be needed to
 // arrange the given list of entries.
-func (layout Vertical) MinimumSize (entries []tomo.LayoutEntry) (width, height int) {
+func (layout Vertical) MinimumSize (
+	entries []tomo.LayoutEntry,
+	squeeze int,
+) (
+	width, height int,
+) {
 	for index, entry := range entries {
 		entryWidth, entryHeight := entry.MinimumSize()
 		if entryWidth > width {

popups/dialog.go

@@ -1,8 +1,8 @@
 package popups
 
 import "git.tebibyte.media/sashakoshka/tomo"
+import "git.tebibyte.media/sashakoshka/tomo/layouts"
 import "git.tebibyte.media/sashakoshka/tomo/elements/basic"
-import "git.tebibyte.media/sashakoshka/tomo/elements/layouts"
 
 // DialogKind defines the semantic role of a dialog window.
 type DialogKind int

tomo.go

@@ -1,165 +1,7 @@
 package tomo
 
-import "image"
 import "errors"
 
-// ParentHooks is a struct that contains callbacks that let child elements send
-// information to their parent element without the child element knowing
-// anything about the parent element or containing any reference to it. When a
-// parent element adopts a child element, it must set these callbacks.
-type ParentHooks struct {
-	// Draw is called when a part of the child element's surface is updated.
-	// The updated region will be passed to the callback as a sub-image.
-	Draw func (region Canvas)
-
-	// MinimumSizeChange is called when the child element's minimum width
-	// and/or height changes. When this function is called, the element will
-	// have already been resized and there is no need to send it a resize
-	// event.
-	MinimumSizeChange func (width, height int)
-
-	// SelectabilityChange is called when the chid element becomes
-	// selectable or non-selectable.
-	SelectabilityChange func (selectable bool)
-
-	// SelectionRequest is called when the child element element wants
-	// itself to be selected. If the parent element chooses to grant the
-	// request, it must send the child element a selection event and return
-	// true.
-	SelectionRequest func () (granted bool)
-}
-
-// RunDraw runs the Draw hook if it is not nil. If it is nil, it does nothing.
-func (hooks ParentHooks) RunDraw (region Canvas) {
-	if hooks.Draw != nil {
-		hooks.Draw(region)
-	}
-}
-
-// RunMinimumSizeChange runs the MinimumSizeChange hook if it is not nil. If it
-// is nil, it does nothing.
-func (hooks ParentHooks) RunMinimumSizeChange (width, height int) {
-	if hooks.MinimumSizeChange != nil {
-		hooks.MinimumSizeChange(width, height)
-	}
-}
-
-// RunSelectionRequest runs the SelectionRequest hook if it is not nil. If it is
-// nil, it does nothing.
-func (hooks ParentHooks) RunSelectionRequest () (granted bool) {
-	if hooks.SelectionRequest != nil {
-		granted = hooks.SelectionRequest()
-	}
-	return
-}
-
-// RunSelectabilityChange runs the SelectionRequest hook if it is not nil. If it
-// is nil, it does nothing.
-func (hooks ParentHooks) RunSelectabilityChange (selectable bool) {
-	if hooks.SelectabilityChange != nil {
-		hooks.SelectabilityChange(selectable)
-	}
-}
-
-// Element represents a basic on-screen object.
-type Element interface {
-	// Element must implement the Canvas interface. Elements should start
-	// out with a completely blank buffer, and only allocate memory and draw
-	// on it for the first time when sent an EventResize event.
-	Canvas
-
-	// Handle handles an event, propagating it to children if necessary.
-	Handle (event Event)
-
-	// Selectable returns whether this element can be selected. If this
-	// element contains other selectable elements, it must return true.
-	Selectable () (selectable bool)
-
-	// Selected returns whether or not this element is currently selected.
-	// This will always return false if it is not selectable.
-	Selected () (selected bool)
-
-	// If this element contains other elements, and one is selected, this
-	// method will advance the selection in the specified direction. If
-	// the element contains selectable elements but none of them are
-	// selected, it will select the first selectable element. If there are
-	// no more children to be selected in the specified direction, the
-	// element will return false. If the selection could be advanced, it
-	// will return true. If the element contains no selectable child
-	// elements, it will  always return false.
-	AdvanceSelection (direction int) (ok bool)
-
-	// SetParentHooks gives the element callbacks that let it send
-	// information to its parent element without it knowing anything about
-	// the parent element or containing any reference to it. When a parent
-	// element adopts a child element, it must set these callbacks.
-	SetParentHooks (callbacks ParentHooks)
-
-	// MinimumSize specifies the minimum amount of pixels this element's
-	// width and height may be set to. If the element is given a resize
-	// event with dimensions smaller than this, it will use its minimum
-	// instead of the offending dimension(s).
-	MinimumSize () (width, height int)
-}
-
-// Window represents a top-level container generated by the currently running
-// backend. It can contain a single element. It is hidden by default, and must
-// be explicitly shown with the Show() method. If it contains no element, it
-// displays a black (or transprent) background.
-type Window interface {
-	// Adopt sets the root element of the window. There can only be one of
-	// these at one time.
-	Adopt (child Element)
-
-	// Child returns the root element of the window.
-	Child () (child Element)
-
-	// SetTitle sets the title that appears on the window's title bar. This
-	// method might have no effect with some backends.
-	SetTitle (title string)
-
-	// SetIcon taks in a list different sizes of the same icon and selects
-	// the best one to display on the window title bar, dock, or whatever is
-	// applicable for the given backend. This method might have no effect
-	// for some backends.
-	SetIcon (sizes []image.Image)
-
-	// Show shows the window. The window starts off hidden, so this must be
-	// called after initial setup to make sure it is visible.
-	Show ()
-
-	// Hide hides the window.
-	Hide ()
-
-	// Close closes the window.
-	Close ()
-
-	// OnClose specifies a function to be called when the window is closed.
-	OnClose (func ())
-}
-
-// LayoutEntry associates an element with layout and positioning information so
-// it can be arranged by a Layout.
-type LayoutEntry struct {
-	Element
-	Position image.Point
-	Expand bool
-}
-
-// Layout is capable of arranging elements within a container. It is also able
-// to determine the minimum amount of room it needs to do so.
-type Layout interface {
-	// Arrange takes in a slice of entries and a bounding width and height,
-	// and changes the position of the entiries in the slice so that they
-	// are properly laid out. The given width and height should not be less
-	// than what is returned by MinimumSize.
-	Arrange (entries []LayoutEntry, width, height int)
-
-	// MinimumSize returns the minimum width and height that the layout
-	// needs to properly arrange the given slice of layout entries.
-	MinimumSize (entries []LayoutEntry) (width, height int)
-}
-
 var backend Backend
 
 // Run initializes a backend, calls the callback function, and begins the event

window.go

@@ -0,0 +1,39 @@
+package tomo
+
+import "image"
+
+// Window represents a top-level container generated by the currently running
+// backend. It can contain a single element. It is hidden by default, and must
+// be explicitly shown with the Show() method. If it contains no element, it
+// displays a black (or transprent) background.
+type Window interface {
+	// Adopt sets the root element of the window. There can only be one of
+	// these at one time.
+	Adopt (child Element)
+
+	// Child returns the root element of the window.
+	Child () (child Element)
+
+	// SetTitle sets the title that appears on the window's title bar. This
+	// method might have no effect with some backends.
+	SetTitle (title string)
+
+	// SetIcon taks in a list different sizes of the same icon and selects
+	// the best one to display on the window title bar, dock, or whatever is
+	// applicable for the given backend. This method might have no effect
+	// for some backends.
+	SetIcon (sizes []image.Image)
+
+	// Show shows the window. The window starts off hidden, so this must be
+	// called after initial setup to make sure it is visible.
+	Show ()
+
+	// Hide hides the window.
+	Hide ()
+
+	// Close closes the window.
+	Close ()
+
+	// OnClose specifies a function to be called when the window is closed.
+	OnClose (func ())
+}