Add translator mechanism

ClickableWidgets.go

@@ -69,7 +69,7 @@ func (b *ButtonWidget) Build() {
 		defer imgui.EndDisabled()
 	}
 
-	if imgui.ButtonV(Context.FontAtlas.RegisterString(b.id.String()), imgui.Vec2{X: b.width, Y: b.height}) && b.onClick != nil {
+	if imgui.ButtonV(Context.PrepareString(b.id.String()), imgui.Vec2{X: b.width, Y: b.height}) && b.onClick != nil {
 		b.onClick()
 	}
 }
@@ -141,7 +141,7 @@ func (b *SmallButtonWidget) OnClick(onClick func()) *SmallButtonWidget {
 
 // Build implements Widget interface.
 func (b *SmallButtonWidget) Build() {
-	if imgui.SmallButton(Context.FontAtlas.RegisterString(b.id.String())) && b.onClick != nil {
+	if imgui.SmallButton(Context.PrepareString(b.id.String())) && b.onClick != nil {
 		b.onClick()
 	}
 }
@@ -381,7 +381,7 @@ func (c *CheckboxWidget) OnChange(onChange func()) *CheckboxWidget {
 
 // Build implements Widget interface.
 func (c *CheckboxWidget) Build() {
-	if imgui.Checkbox(Context.FontAtlas.RegisterString(c.text.String()), c.selected) && c.onChange != nil {
+	if imgui.Checkbox(Context.PrepareString(c.text.String()), c.selected) && c.onChange != nil {
 		c.onChange()
 	}
 }
@@ -414,7 +414,7 @@ func (r *RadioButtonWidget) OnChange(onChange func()) *RadioButtonWidget {
 
 // Build implements Widget interface.
 func (r *RadioButtonWidget) Build() {
-	if imgui.RadioButtonBool(Context.FontAtlas.RegisterString(r.text.String()), r.active) && r.onChange != nil {
+	if imgui.RadioButtonBool(Context.PrepareString(r.text.String()), r.active) && r.onChange != nil {
 		r.onChange()
 	}
 }
@@ -489,7 +489,7 @@ func (s *SelectableWidget) Build() {
 		s.flags |= SelectableFlagsAllowDoubleClick
 	}
 
-	if imgui.SelectableBoolV(Context.FontAtlas.RegisterString(s.label.String()), s.selected, imgui.SelectableFlags(s.flags), imgui.Vec2{X: s.width, Y: s.height}) && s.onClick != nil {
+	if imgui.SelectableBoolV(Context.PrepareString(s.label.String()), s.selected, imgui.SelectableFlags(s.flags), imgui.Vec2{X: s.width, Y: s.height}) && s.onClick != nil {
 		s.onClick()
 	}
 
@@ -514,7 +514,7 @@ type TreeNodeWidget struct {
 // TreeNode creates a new tree node widget.
 func TreeNode(label string) *TreeNodeWidget {
 	return &TreeNodeWidget{
-		label:        Context.FontAtlas.RegisterString(label),
+		label:        label,
 		flags:        0,
 		layout:       nil,
 		eventHandler: nil,
@@ -554,7 +554,7 @@ func (t *TreeNodeWidget) Layout(widgets ...Widget) *TreeNodeWidget {
 
 // Build implements Widget interface.
 func (t *TreeNodeWidget) Build() {
-	open := imgui.TreeNodeExStrV(t.label, imgui.TreeNodeFlags(t.flags))
+	open := imgui.TreeNodeExStrV(Context.PrepareString(t.label), imgui.TreeNodeFlags(t.flags))
 
 	if t.event != nil {
 		t.event()

Context.go

@@ -69,6 +69,7 @@ type GIUContext struct {
 
 	InputHandler InputHandler
 	FontAtlas    *FontAtlas
+	Translator   Translator
 
 	textureLoadingQueue *queue.Queue
 	textureFreeingQueue *queue.Queue
@@ -87,6 +88,7 @@ func CreateContext(b backend.Backend[glfwbackend.GLFWWindowFlags]) *GIUContext {
 		textureLoadingQueue: queue.New(),
 		textureFreeingQueue: queue.New(),
 		m:                   &sync.Mutex{},
+		Translator:          &EmptyTranslator{},
 	}
 
 	// Create font
@@ -114,6 +116,16 @@ func (c *GIUContext) SetDirty() {
 	c.dirty = true
 }
 
+// PrepareString prepares string to be displayed by imgui.
+// It does the following:
+// - adds a string to the FontAtlas
+// - translates the string with the Translator set in the context
+// Not all widgets will use this. Text with user-defined input (e.g. InputText will still use FontAtlas.RegisterString).
+func (c *GIUContext) PrepareString(str string) string {
+	str = c.Translator.Translate(str)
+	return c.FontAtlas.RegisterString(str)
+}
+
 // cleanStates removes all states that were not marked as valid during rendering,
 // then reset said flag before new usage
 // should always be called before first Get/Set state use in renderloop

FontAtlasProsessor.go

@@ -218,6 +218,7 @@ func (a *FontAtlas) registerDefaultFonts(fontInfos []FontInfo) {
 
 // RegisterString register string to font atlas builder.
 // Note only register strings that will be displayed on the UI.
+// This also calls translator before registering the string.
 func (a *FontAtlas) RegisterString(str string) string {
 	for _, s := range str {
 		if _, ok := a.stringMap.Load(s); !ok {

TextWidgets.go

@@ -132,7 +132,7 @@ type BulletTextWidget struct {
 // BulletText creates bulletTextWidget.
 func BulletText(text string) *BulletTextWidget {
 	return &BulletTextWidget{
-		text: Context.FontAtlas.RegisterString(text),
+		text: Context.PrepareString(text),
 	}
 }
 
@@ -526,7 +526,7 @@ type LabelWidget struct {
 // Label constructs label widget.
 func Label(label string) *LabelWidget {
 	return &LabelWidget{
-		label:   Context.FontAtlas.RegisterString(label),
+		label:   Context.PrepareString(label),
 		wrapped: false,
 	}
 }

Translator.go

@@ -0,0 +1,102 @@
+package giu
+
+import (
+	"strings"
+)
+
+// Translator should be implemented by type that can translate a string to another string.
+type Translator interface {
+	// Translate returns tranalted string
+	Translate(string) string
+	// SetLanguage changes language of the translation.
+	SetLanguage(string) error
+}
+
+// SetTranslator allows to change the default (&EmptyTranslator{})
+// This will raise a panic if t is nil.
+// Note that using translator will change labels of widgets,
+// so this might affect internal imgui's state.
+// See also Context.RegisterString.
+func (c *GIUContext) SetTranslator(t Translator) {
+	Assert(t != nil, "Context", "SetTranslator", "Translator must not be nil.")
+	c.Translator = t
+}
+
+var _ Translator = &EmptyTranslator{}
+
+// EmptyTranslator is the default one (to save resources).
+// It does nothing.
+type EmptyTranslator struct{}
+
+// Translate implements Translator interface.
+func (t *EmptyTranslator) Translate(s string) string {
+	return s
+}
+
+// SetLanguage implements Translator interface.
+func (t *EmptyTranslator) SetLanguage(_ string) error {
+	return nil
+}
+
+var _ Translator = &BasicTranslator{}
+
+// BasicTranslator is a simpliest implementation of translation mechanism.
+// This is NOT thread-safe yet. If you need thread-safety, write your own implementation.
+//
+// It is supposed to be used in the following way:
+// - create translator
+// - add languages (tip: you can use empty map for default language)
+// - set translator in Context
+// - set default language
+// - write your UI as always.
+type BasicTranslator struct {
+	// language tag -> key -> value
+	source          map[string]map[string]string
+	currentLanguage string
+}
+
+// NewBasicTranslator creates a new BasicTranslator with the given language tag.
+func NewBasicTranslator() *BasicTranslator {
+	return &BasicTranslator{}
+}
+
+// Translate implements Translator interface.
+// It translates s to the current language, under the following conditions:
+// - If s is empty, an empty string is returned with no further processing.
+// - If t.currentLanguage is empty, a panic will be raised.
+// - If t.currentLanguage is not in a.source, BasicTranslator raises panic.
+// - If s is not in source[currentLanguage], s is returned as-is.
+func (t *BasicTranslator) Translate(s string) string {
+	s = strings.Split(s, "##")[0]
+	if s == "" {
+		return ""
+	}
+
+	Assert(t.currentLanguage != "", "BasicTranslator", "Translate", "Current language is not set, so there is no sense in using BasicTranslator.")
+	locale, ok := t.source[t.currentLanguage]
+	Assert(ok, "BasicTranslator", "Translate", "There is no language tag %s known by the translator. Did you add it?", t.currentLanguage)
+
+	translated, ok := locale[s]
+	if !ok {
+		return s
+	}
+
+	return translated
+}
+
+// SetLanguage sets the current language of the translator.
+func (t *BasicTranslator) SetLanguage(tag string) error {
+	t.currentLanguage = tag
+	return nil
+}
+
+// AddLanguage adds a new "dictionary" to the translator.
+func (t *BasicTranslator) AddLanguage(tag string, source map[string]string) *BasicTranslator {
+	if t.source == nil {
+		t.source = make(map[string]map[string]string)
+	}
+
+	t.source[tag] = source
+
+	return t
+}

Widgets.go

@@ -149,7 +149,7 @@ func ComboCustom(label, previewValue string) *ComboCustomWidget {
 
 // Layout add combo's layout.
 func (cc *ComboCustomWidget) Layout(widgets ...Widget) *ComboCustomWidget {
-	cc.layout = Layout(widgets)
+	cc.layout = widgets
 	return cc
 }
 
@@ -172,7 +172,7 @@ func (cc *ComboCustomWidget) Build() {
 		defer imgui.PopItemWidth()
 	}
 
-	if imgui.BeginComboV(Context.FontAtlas.RegisterString(cc.label.String()), cc.previewValue, imgui.ComboFlags(cc.flags)) {
+	if imgui.BeginComboV(Context.PrepareString(cc.label.String()), cc.previewValue, imgui.ComboFlags(cc.flags)) {
 		cc.layout.Build()
 		imgui.EndCombo()
 	}
@@ -236,9 +236,9 @@ func (c *ComboWidget) Build() {
 		defer imgui.PopItemWidth()
 	}
 
-	if imgui.BeginComboV(Context.FontAtlas.RegisterString(c.label.String()), c.previewValue, imgui.ComboFlags(c.flags)) {
+	if imgui.BeginComboV(Context.PrepareString(c.label.String()), c.previewValue, imgui.ComboFlags(c.flags)) {
 		for i, item := range c.items {
-			if imgui.SelectableBool(fmt.Sprintf("%s##%d", item, i)) {
+			if imgui.SelectableBool(fmt.Sprintf("%s##%d", Context.PrepareString(item), i)) {
 				*c.selected = int32(i)
 				if c.onChange != nil {
 					c.onChange()
@@ -332,7 +332,7 @@ func (d *DragIntWidget) Format(format string) *DragIntWidget {
 
 // Build implements Widget interface.
 func (d *DragIntWidget) Build() {
-	imgui.DragIntV(Context.FontAtlas.RegisterString(d.label.String()), d.value, d.speed, d.minValue, d.maxValue, d.format, 0)
+	imgui.DragIntV(Context.PrepareString(d.label.String()), d.value, d.speed, d.minValue, d.maxValue, d.format, 0)
 }
 
 var _ Widget = &ColumnWidget{}
@@ -376,7 +376,7 @@ func MainMenuBar() *MainMenuBarWidget {
 
 // Layout sets layout of the menu bar. (See MenuWidget).
 func (m *MainMenuBarWidget) Layout(widgets ...Widget) *MainMenuBarWidget {
-	m.layout = Layout(widgets)
+	m.layout = widgets
 	return m
 }
 
@@ -471,7 +471,7 @@ func (m *MenuItemWidget) OnClick(onClick func()) *MenuItemWidget {
 
 // Build implements Widget interface.
 func (m *MenuItemWidget) Build() {
-	if imgui.MenuItemBoolV(Context.FontAtlas.RegisterString(m.label.String()), m.shortcut, m.selected, m.enabled) && m.onClick != nil {
+	if imgui.MenuItemBoolV(Context.PrepareString(m.label.String()), m.shortcut, m.selected, m.enabled) && m.onClick != nil {
 		m.onClick()
 	}
 }
@@ -514,7 +514,7 @@ func (m *MenuWidget) Layout(widgets ...Widget) *MenuWidget {
 
 // Build implements Widget interface.
 func (m *MenuWidget) Build() {
-	if imgui.BeginMenuV(Context.FontAtlas.RegisterString(m.label.String()), m.enabled) {
+	if imgui.BeginMenuV(Context.PrepareString(m.label.String()), m.enabled) {
 		m.layout.Build()
 		imgui.EndMenu()
 	}
@@ -621,7 +621,7 @@ type TabItemWidget struct {
 // TabItem creates new TabItem.
 func TabItem(label string) *TabItemWidget {
 	return &TabItemWidget{
-		label:  Context.FontAtlas.RegisterString(label),
+		label:  label,
 		open:   nil,
 		flags:  0,
 		layout: nil,
@@ -650,13 +650,16 @@ func (t *TabItemWidget) Flags(flags TabItemFlags) *TabItemWidget {
 
 // Layout is a layout displayed when item is opened.
 func (t *TabItemWidget) Layout(widgets ...Widget) *TabItemWidget {
-	t.layout = Layout(widgets)
+	t.layout = widgets
 	return t
 }
 
 // BuildTabItem executes tab item build steps.
 func (t *TabItemWidget) BuildTabItem() {
-	if imgui.BeginTabItemV(t.label, t.open, imgui.TabItemFlags(t.flags)) {
+	if imgui.BeginTabItemV(
+		Context.PrepareString(t.label),
+		t.open, imgui.TabItemFlags(t.flags),
+	) {
 		t.layout.Build()
 		imgui.EndTabItem()
 	}
@@ -734,7 +737,7 @@ func Tooltipf(format string, args ...any) *TooltipWidget {
 
 // Layout sets a custom layout of tooltip.
 func (t *TooltipWidget) Layout(widgets ...Widget) *TooltipWidget {
-	t.layout = Layout(widgets)
+	t.layout = widgets
 	return t
 }
 
@@ -766,7 +769,7 @@ func (t *TooltipWidget) buildTooltip() {
 			t.layout.Build()
 			imgui.EndTooltip()
 		} else {
-			imgui.SetTooltip(t.tip)
+			imgui.SetTooltip(Context.PrepareString(t.tip))
 		}
 	}
 }
@@ -839,7 +842,7 @@ func (ce *ColorEditWidget) Build() {
 	}
 
 	if imgui.ColorEdit4V(
-		Context.FontAtlas.RegisterString(ce.label.String()),
+		Context.PrepareString(ce.label.String()),
 		&col,
 		imgui.ColorEditFlags(ce.flags),
 	) {

examples/translation/translation.go

@@ -0,0 +1,49 @@
+// Package main shows using of translations in giu.
+package main
+
+import "github.com/AllenDang/giu"
+
+var (
+	// here we define our multi-language dictionary.
+	// You could also do that e.g. with JSON.
+	languageDefs = map[string]map[string]string{
+		"en": {}, // as we write our UI in english, the default value of the text will be fine (see (*BasicTranslator).Translate for more)
+		"pl": {
+			"Hello world!": "Witaj świecie",
+		},
+		"de": {
+			"Hello world!": "Hallo Welt!",
+		},
+	}
+
+	languageCodes = []string{"en", "pl", "de"}
+	currentLang   int32
+)
+
+func loop() {
+	giu.SingleWindow().Layout(
+		giu.Combo("Select language", languageCodes[currentLang], languageCodes, &currentLang).OnChange(func() {
+			if err := giu.Context.Translator.SetLanguage(languageCodes[currentLang]); err != nil {
+				panic(err)
+			}
+		}),
+		giu.Label("Hello world!"),
+	)
+}
+
+func main() {
+	wnd := giu.NewMasterWindow("Hello world", 800, 600, giu.MasterWindowFlagsNotResizable)
+	// initialize translation. Do that before loop.
+	translator := giu.NewBasicTranslator()
+	for k, v := range languageDefs {
+		translator.AddLanguage(k, v)
+	}
+
+	if err := translator.SetLanguage(languageCodes[currentLang]); err != nil {
+		panic(err)
+	}
+
+	giu.Context.SetTranslator(translator)
+
+	wnd.Run(loop)
+}