Support change detection (#69)

Author: magicoder10

ui/background.go

@@ -1,15 +1,49 @@
 package ui
 
 import (
+	"image"
 	"image/draw"
+
+	"candy/assets"
 )
 
 type Background struct {
-	Color *Color
+	Color     *Color
+	ImagePath *string
+
+	prevColor     Color
+	prevImagePath string
+
+	image      image.Image
+	hasChanged bool
 }
 
 func (b Background) Paint(painter *Painter, destLayer draw.Image) {
+	if b.ImagePath != nil {
+		return
+	}
 	if b.Color != nil {
 		painter.fillColor(destLayer, *b.Color)
 	}
 }
+
+func (b *Background) Update(assets *assets.Assets) {
+	if b.ImagePath != nil {
+		imagePath := *b.ImagePath
+		if imagePath != b.prevImagePath {
+			b.image = assets.GetImage(imagePath)
+			b.hasChanged = true
+			b.prevImagePath = *b.ImagePath
+		}
+	}
+	if b.Color != nil {
+		if *b.Color == b.prevColor {
+			b.hasChanged = true
+			b.prevColor = *b.Color
+		}
+	}
+}
+
+func (b *Background) ResetChangeDetection() {
+	b.hasChanged = false
+}

ui/box.go

@@ -23,6 +23,10 @@ func (b Box) GetName() string {
 }
 
 func (b Box) Paint(painter *Painter, destLayer draw.Image, offset Offset) {
+	if !b.hasChanged {
+		return
+	}
+
 	contentLayer := image.NewRGBA(image.Rectangle{
 		Max: image.Point{
 			X: b.size.width,
@@ -88,7 +92,7 @@ func NewBox(pros *BoxProps, children []Component, style *Style) *Box {
 		SharedComponent: SharedComponent{
 			name:           "Box",
 			layout:         newLayout(*style.LayoutType),
-			style:          *style,
+			style:          style,
 			children:       children,
 			childrenOffset: []Offset{},
 			events:         Events{onClick: pros.OnClick},

ui/change.go

@@ -0,0 +1,5 @@
+package ui
+
+type Changeable interface {
+	hasChanged() bool
+}

ui/component.go

@@ -5,14 +5,20 @@ import (
 	"image/draw"
 	"time"
 
+	"candy/assets"
 	"candy/input"
 )
 
+type UpdateDeps struct {
+	assets *assets.Assets
+	fonts  *Fonts
+}
+
 type Component interface {
 	GetName() string
 	HandleInput(in input.Input)
 	handleInput(in input.Input, offset Offset)
-	Update(timeElapsed time.Duration)
+	Update(timeElapsed time.Duration, deps *UpdateDeps)
 	getLayout() layout
 	getChildren() []Component
 	ComputeLeafSize(constraints Constraints) Size
@@ -21,6 +27,8 @@ type Component interface {
 	getStyle() Style
 	getChildrenOffset() []Offset
 	setChildrenOffset(childrenOffsets []Offset)
+	HasChanged() bool
+	ResetChangeDetection()
 	Paint(painter *Painter, destLayer draw.Image, offset Offset)
 }
 
@@ -38,11 +46,12 @@ type Offset struct {
 type SharedComponent struct {
 	name           string
 	layout         layout
-	style          Style
+	style          *Style
 	size           Size
 	childrenOffset []Offset
 	children       []Component
 	events         Events
+	hasChanged     bool
 }
 
 func (s *SharedComponent) HandleInput(in input.Input) {
@@ -74,10 +83,34 @@ func (s *SharedComponent) BoundingBox(offset Offset) image.Rectangle {
 	return image.Rect(offset.x, offset.y, offset.x+s.size.width, offset.y+s.size.height)
 }
 
-func (s SharedComponent) Update(timeElapsed time.Duration) {
+func (s *SharedComponent) Update(timeElapsed time.Duration, deps *UpdateDeps) {
+	for _, child := range s.children {
+		child.Update(timeElapsed, deps)
+		if child.HasChanged() {
+			s.hasChanged = true
+		}
+	}
+	if s.style != nil {
+		s.style.Update(deps)
+		if s.style.hasChanged {
+			s.hasChanged = true
+		}
+	}
+}
+
+func (s SharedComponent) HasChanged() bool {
+	return s.hasChanged
+}
+
+func (s *SharedComponent) ResetChangeDetection() {
 	for _, child := range s.children {
-		child.Update(timeElapsed)
+		child.ResetChangeDetection()
 	}
+
+	if s.style != nil {
+		s.style.ResetChangeDetection()
+	}
+	s.hasChanged = false
 }
 
 func (s SharedComponent) GetName() string {
@@ -105,7 +138,10 @@ func (s *SharedComponent) setSize(size Size) {
 }
 
 func (s SharedComponent) getStyle() Style {
-	return s.style
+	if s.style == nil {
+		return Style{}
+	}
+	return *s.style
 }
 
 func (s *SharedComponent) setChildrenOffset(childrenOffsets []Offset) {

ui/engine.go

@@ -6,6 +6,7 @@ import (
 	"image/draw"
 	"time"
 
+	"candy/assets"
 	"candy/graphics"
 	"candy/input"
 	"candy/observability"
@@ -20,8 +21,8 @@ type RenderEngine struct {
 	rootComponent   Component
 	rootConstraints Constraints
 	compositeLayer  draw.Image
-	hasUpdate       bool
 	batch           graphics.Batch
+	updateDeps      *UpdateDeps
 }
 
 func (r *RenderEngine) Render(component Component) {
@@ -37,7 +38,7 @@ func (r *RenderEngine) Update(timeElapsed time.Duration) {
 	if r.rootComponent == nil {
 		return
 	}
-	r.rootComponent.Update(timeElapsed)
+	r.rootComponent.Update(timeElapsed, r.updateDeps)
 }
 
 func (r *RenderEngine) HandleInput(in input.Input) {
@@ -48,7 +49,10 @@ func (r *RenderEngine) HandleInput(in input.Input) {
 }
 
 func (r *RenderEngine) render() {
-	if !r.hasUpdate {
+	if r.rootComponent == nil {
+		return
+	}
+	if !r.rootComponent.HasChanged() {
 		return
 	}
 
@@ -63,7 +67,8 @@ func (r *RenderEngine) render() {
 	r.rootComponent.Paint(r.painter, r.compositeLayer, Offset{})
 
 	r.batch = r.graphics.StartNewBatch(r.compositeLayer)
-	r.hasUpdate = false
+
+	r.rootComponent.ResetChangeDetection()
 }
 
 func (r *RenderEngine) draw() {
@@ -82,15 +87,19 @@ func (r RenderEngine) generateLayout(component Component) {
 }
 
 func NewRenderEngine(
+	rootConstraints Constraints,
 	logger *observability.Logger,
 	g graphics.Graphics,
-	rootConstraints Constraints,
+	assets *assets.Assets,
 ) *RenderEngine {
 	return &RenderEngine{
 		logger:          logger,
 		graphics:        g,
 		painter:         &Painter{},
 		rootConstraints: rootConstraints,
-		hasUpdate:       true,
+		updateDeps: &UpdateDeps{
+			assets: assets,
+			fonts:  NewFonts(),
+		},
 	}
 }

ui/example/app.go

@@ -3,7 +3,6 @@ package main
 import (
 	"fmt"
 
-	"candy/assets"
 	"candy/ui"
 	"candy/ui/ptr"
 )
@@ -14,7 +13,7 @@ type app struct {
 	*ui.Box
 }
 
-func newApp(assets *assets.Assets) *app {
+func newApp() *app {
 	return &app{ui.NewBox(
 		&ui.BoxProps{OnClick: func() {
 			fmt.Println("Box clicked")
@@ -37,7 +36,7 @@ determination that "meant to be" is exactly as meaningless a phrase as it
 seems to be, and that none of us is actually meant to be doing anything at all. 
 But that's my existential underpants underpinnings showing. It's the way the 
 cookie crumbles. And now I want a cookie.
-`}, &ui.Style{FontStyle: ui.FontStyle{
+`}, &ui.Style{FontStyle: &ui.FontStyle{
 				Family:     ptr.String("Source Code Pro"),
 				Weight:     ptr.String("ExtraLight"),
 				Italic:     ptr.Bool(false),
@@ -49,9 +48,9 @@ cookie crumbles. And now I want a cookie.
 					Blue:  255,
 					Alpha: 255,
 				}}}),
-			ui.NewImage(assets, &ui.ImageProps{ImagePath: "test/image3.png"}, nil),
-			ui.NewImage(assets, &ui.ImageProps{ImagePath: "test/image1.jpg"}, nil),
-			ui.NewImage(assets, &ui.ImageProps{ImagePath: "test/image2.jpg"}, nil),
+			ui.NewImage(&ui.ImageProps{ImagePath: "test/image3.png"}, nil),
+			ui.NewImage(&ui.ImageProps{ImagePath: "test/image1.jpg"}, nil),
+			ui.NewImage(&ui.ImageProps{ImagePath: "test/image2.jpg"}, nil),
 		},
 		nil)}
 }

ui/example/main.go

@@ -25,8 +25,8 @@ func main() {
 	logger := observability.NewLogger(observability.Debug)
 	rootConstraint := ui.NewScreenConstraint(screenWidth, screenHeight)
 
-	renderEngine := ui.NewRenderEngine(&logger, &eb, rootConstraint)
-	renderEngine.Render(newApp(&ass))
+	renderEngine := ui.NewRenderEngine(rootConstraint, &logger, &eb, &ass)
+	renderEngine.Render(newApp())
 
 	g := graphics.NewEbitenWindow(graphics.WindowConfig{
 		Width:  screenWidth,

ui/font.go

@@ -9,6 +9,37 @@ import (
 	"golang.org/x/image/font"
 )
 
+type Fonts struct {
+	fontFinder *sysfont.Finder
+	families   map[string]*fontFamily
+}
+
+func (f *Fonts) getFamily(familyName string) *fontFamily {
+	f.loadFont(familyName)
+	matchedFont := f.fontFinder.Match(familyName)
+	return f.families[matchedFont.Family]
+}
+
+func (f *Fonts) loadFont(familyName string) {
+	matchedFont := f.fontFinder.Match(familyName)
+	if _, ok := f.families[matchedFont.Family]; ok {
+		return
+	}
+	ff, err := newFontFamily(f.fontFinder, matchedFont.Family)
+	if err != nil {
+		return
+	}
+	f.families[matchedFont.Family] = &ff
+}
+
+func NewFonts() *Fonts {
+	finder := sysfont.NewFinder(nil)
+	return &Fonts{
+		fontFinder: finder,
+		families:   make(map[string]*fontFamily, 0),
+	}
+}
+
 type fontFamily struct {
 	dpi        int
 	fontFinder *sysfont.Finder
@@ -21,14 +52,14 @@ type fontStyle struct {
 	italic bool
 }
 
-func (f fontFamily) face(style fontStyle, fontSize int) (*truetype.Font, fontFace, error) {
+func (f fontFamily) face(style fontStyle, fontSize int) (*truetype.Font, *fontFace, error) {
 	ft, err := f.getFont(style)
 	if err != nil {
-		return nil, fontFace{}, err
+		return nil, nil, err
 	}
 	options := truetype.Options{Size: float64(fontSize), DPI: float64(f.dpi)}
 	face := truetype.NewFace(ft, &options)
-	return ft, fontFace{fontFace: face}, nil
+	return ft, &fontFace{fontFace: face}, nil
 }
 
 func (f fontFamily) getFont(style fontStyle) (*truetype.Font, error) {
@@ -43,18 +74,14 @@ func (f fontFamily) getQuery(style fontStyle) string {
 	return f.fontFamily + style.toString()
 }
 
-func findFontFamily(fontFinder *sysfont.Finder, fontFamily string) (string, []*sysfont.Font) {
-	matchedFont := fontFinder.Match(fontFamily)
-	if matchedFont == nil {
-		return "", []*sysfont.Font{}
-	}
+func findFontFamily(fontFinder *sysfont.Finder, family string) (string, []*sysfont.Font) {
 	fonts := make([]*sysfont.Font, 0)
 	for _, fontInstalled := range fontFinder.List() {
-		if matchedFont.Family == fontInstalled.Family {
+		if family == fontInstalled.Family {
 			fonts = append(fonts, fontInstalled)
 		}
 	}
-	return matchedFont.Family, fonts
+	return family, fonts
 }
 
 func loadFonts(fonts []*sysfont.Font) (map[sysfont.Font]*truetype.Font, error) {
@@ -73,11 +100,10 @@ func loadFonts(fonts []*sysfont.Font) (map[sysfont.Font]*truetype.Font, error) {
 	return parsedFonts, nil
 }
 
-func newFontFamily(fontFamilyName string) (fontFamily, error) {
-	finder := sysfont.NewFinder(nil)
-	familyName, fontsInFamily := findFontFamily(finder, fontFamilyName)
+func newFontFamily(fontFinder *sysfont.Finder, family string) (fontFamily, error) {
+	familyName, fontsInFamily := findFontFamily(fontFinder, family)
 	if len(fontsInFamily) < 1 {
-		return fontFamily{}, fmt.Errorf("font family not found: %s", fontFamilyName)
+		return fontFamily{}, fmt.Errorf("font family not found: %s", family)
 	}
 
 	fonts, err := loadFonts(fontsInFamily)
@@ -87,7 +113,7 @@ func newFontFamily(fontFamilyName string) (fontFamily, error) {
 	return fontFamily{
 		dpi:        72,
 		fontFamily: familyName,
-		fontFinder: finder,
+		fontFinder: fontFinder,
 		fonts:      fonts,
 	}, nil
 }