Split element core into two separate structs - public and private

The public core half can be directly embedded, which means no
wrapper methods!

elements/basic/button.go

@@ -7,7 +7,9 @@ import "git.tebibyte.media/sashakoshka/tomo/theme"
 import "git.tebibyte.media/sashakoshka/tomo/artist"
 
 type Button struct {
-	core    Core
+	*Core
+	core CoreControl
+	
 	pressed bool
 	enabled bool
 	onClick func ()
@@ -18,7 +20,7 @@ type Button struct {
 
 func NewButton (text string) (element *Button) {
 	element = &Button { enabled: true }
-	element.core = NewCore(element)
+	element.Core, element.core = NewCore(element)
 	element.drawer.SetFace(theme.FontFaceRegular())
 	element.SetText(text)
 	return
@@ -94,48 +96,12 @@ func (element *Button) OnClick (callback func ()) {
 	element.onClick = callback
 }
 
-func (element *Button) ColorModel () (model color.Model) {
+func (element *Button) AdvanceSelection (direction int) (ok bool) {
-	return color.RGBAModel
-}
-
-func (element *Button) At (x, y int) (pixel color.Color) {
-	pixel = element.core.At(x, y)
 	return
 }
 
-func (element *Button) RGBAAt (x, y int) (pixel color.RGBA) {
-	pixel = element.core.RGBAAt(x, y)
-	return
-}
-
-func (element *Button) Bounds () (bounds image.Rectangle) {
-	bounds = element.core.Bounds()
-	return
-}
-
-func (element *Button) SetDrawCallback (draw func (region tomo.Image)) {
-	element.core.SetDrawCallback(draw)
-}
-
-func (element *Button) SetMinimumSizeChangeCallback (
-	notify func (width, height int),
-) {
-	element.core.SetMinimumSizeChangeCallback(notify)
-}
-
 func (element *Button) Selectable () (selectable bool) {
-	selectable = true
+	return true
-	return
-}
-
-func (element *Button) MinimumWidth () (minimum int) {
-	minimum = element.core.MinimumWidth()
-	return
-}
-
-func (element *Button) MinimumHeight () (minimum int) {
-	minimum = element.core.MinimumHeight()
-	return
 }
 
 func (element *Button) draw () {

elements/basic/core.go

@@ -5,24 +5,23 @@ import "image/color"
 import "git.tebibyte.media/sashakoshka/tomo"
 
 // Core is a struct that implements some core functionality common to most
-// widgets. It is possible to embed this directly into a struct, but this is not
+// widgets. It is meant to be embedded directly into a struct.
-// reccomended as it exposes internal functionality.
 type Core struct {
-	*image.RGBA
+	canvas *image.RGBA
 	parent tomo.Element
-	
-	drawCallback func (region tomo.Image)
-	minimumSizeChangeCallback func (width, height int)
 
 	metrics struct {
 		minimumWidth  int
 		minimumHeight int
 	}
+
+	hooks tomo.ParentHooks
 }
 
-// Core creates a new element core.
+// NewCore creates a new element core and its corresponding control.
-func NewCore (parent tomo.Element) (core Core) {
+func NewCore (parent tomo.Element) (core *Core, control CoreControl) {
-	core = Core { parent: parent }
+	core    = &Core { parent: parent }
+	control = CoreControl { core: core }
 	return
 }
 
@@ -31,81 +30,75 @@ func (core Core) ColorModel () (model color.Model) {
 }
 
 func (core Core) At (x, y int) (pixel color.Color) {
-	if core.RGBA == nil { return color.RGBA { } }
+	if core.canvas == nil { return color.RGBA { } }
-	pixel = core.RGBA.At(x, y)
+	pixel = core.canvas.At(x, y)
 	return
 }
 
 func (core Core) RGBAAt (x, y int) (pixel color.RGBA) {
-	if core.RGBA == nil { return color.RGBA { } }
+	if core.canvas == nil { return color.RGBA { } }
-	pixel = core.RGBA.RGBAAt(x, y)
+	pixel = core.canvas.RGBAAt(x, y)
 	return
 }
 
 func (core Core) Bounds () (bounds image.Rectangle) {
-	if core.RGBA != nil { bounds = core.RGBA.Bounds() }
+	if core.canvas != nil { bounds = core.canvas.Bounds() }
 	return
 }
 
-func (core *Core) SetDrawCallback (draw func (region tomo.Image)) {
+func (core *Core) SetParentHooks (hooks tomo.ParentHooks) {
-	core.drawCallback = draw
+	core.hooks = hooks
 }
 
-func (core *Core) SetMinimumSizeChangeCallback (
+func (core Core) MinimumSize () (width, height int) {
-	notify func (width, height int),
+	return core.metrics.minimumWidth, core.metrics.minimumHeight
-) {
-	core.minimumSizeChangeCallback = notify
 }
 
-func (core Core) HasImage () (has bool) {
+// CoreControl is a struct that can exert control over a control struct. It can
-	has = core.RGBA != nil
+// be used as a canvas. It must not be directly embedded into an element, but
+// instead kept as a private member.
+type CoreControl struct {
+	*image.RGBA
+	core *Core
+}
+
+func (control CoreControl) HasImage () (has bool) {
+	has = control.RGBA != nil
 	return
 }
 
-func (core Core) PushRegion (bounds image.Rectangle) {
+func (control CoreControl) PushRegion (bounds image.Rectangle) {
-	if core.drawCallback != nil {
+	core := control.core
-		core.drawCallback(core.SubImage(bounds).
+	core.hooks.RunDraw(control.SubImage(bounds).(*image.RGBA))
-			(*image.RGBA))
-	}
 }
 
-func (core Core) PushAll () {
+func (control CoreControl) PushAll () {
-	core.PushRegion(core.Bounds())
+	control.PushRegion(control.Bounds())
 }
 
-func (core *Core) AllocateCanvas (width, height int) {
+func (control CoreControl) AllocateCanvas (width, height int) {
-	width, height, _ = core.ConstrainSize(width, height)
+	core := control.core
-	core.RGBA = image.NewRGBA(image.Rect (0, 0, width, height))
+	width, height, _ = control.ConstrainSize(width, height)
+	core.canvas  = image.NewRGBA(image.Rect (0, 0, width, height))
+	control.RGBA = core.canvas
 }
 
-func (core Core) MinimumWidth () (minimum int) {
+func (control CoreControl) SetMinimumSize (width, height int) {
-	minimum = core.metrics.minimumWidth
+	core := control.core
-	return
-}
-
-func (core Core) MinimumHeight () (minimum int) {
-	minimum = core.metrics.minimumHeight
-	return
-}
-
-func (core *Core) SetMinimumSize (width, height int) {
 	if width != core.metrics.minimumWidth ||
 		height != core.metrics.minimumHeight {
 
 		core.metrics.minimumWidth  = width
 		core.metrics.minimumHeight = height
-		
+		core.hooks.RunMinimumSizeChange(width, height)
-		if core.minimumSizeChangeCallback != nil {
-			core.minimumSizeChangeCallback(width, height)
-		}
 
 		// if there is an image buffer, and the current size is less
 		// than this new minimum size, send core.parent a resize event.
-		if core.HasImage() {
+		if control.HasImage() {
-			bounds := core.Bounds()
+			bounds := control.Bounds()
 			imageWidth,
 			imageHeight,
-			constrained := core.ConstrainSize (
+			constrained := control.ConstrainSize (
 				bounds.Dx(),
 				bounds.Dy())
 			if constrained {
@@ -118,12 +111,13 @@ func (core *Core) SetMinimumSize (width, height int) {
 	}
 }
 
-func (core Core) ConstrainSize (
+func (control CoreControl) ConstrainSize (
 	inWidth, inHeight int,
 ) (
 	outWidth, outHeight int,
 	constrained bool,
 ) {
+	core := control.core
 	outWidth  = inWidth
 	outHeight = inHeight
 	if outWidth < core.metrics.minimumWidth {

tomo.go

@@ -121,7 +121,7 @@ type Window interface {
 	// 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
-	// with some backends.
+	// for some backends.
 	SetIcon (sizes []image.Image)
 
 	// Show shows the window. The window starts off hidden, so this must be