Theming

// Light theme (default)
ui.Run("App", build)

// Dark theme
ui.Run("App", build, ui.Dark())

// Custom theme
ui.Run("App", build, ui.Theme(myTheme))

app.New("App").Run()                              // Light (default)
app.New("App").WithDarkTheme().Run()              // Dark
app.New("App").WithTheme(theme.FluentDark()).Run() // Explicit

type Theme struct {
    Palette Palette       // Colors
    Typo    Typography    // Text styles
    Space   Spacing       // Standard spacing values
    Corner  CornerRadius  // Border radius values
    Elev    Elevation     // Shadow/depth values
    Shaper  *text.Shaper  // Text renderer (managed internally)
}

ui.Themed(func(th *theme.Theme) ui.View {
    return ui.Text("Accent colored").Color(th.Palette.Primary)
})

func myLayout(gtx layout.Context, th *theme.Theme) layout.Dimensions {
    col := th.Palette.Primary
    // use col...
}

ui.RGB(255, 0, 0)           // Opaque red
ui.RGBA(255, 0, 0, 128)     // 50% transparent red
ui.Hex("#FF0000")            // From hex string
ui.Hex("F00")               // 3-digit hex

ui.Text("Title").Headline()   // HeadlineLarge
ui.Text("Title").Title()      // HeadlineMedium
ui.Text("Bold").Bold()        // TitleMedium
ui.Text("Caption").Caption()  // LabelSmall
ui.Text("Small").Small()      // BodySmall
ui.Text("Hero").Display()     // DisplayLarge

widget.H1("Title")     // HeadlineLarge
widget.H2("Heading")   // HeadlineMedium
widget.H3("Subtitle")  // TitleMedium
widget.Body("Text")    // BodyMedium
widget.Caption("Hint") // LabelSmall

themeRef := ui.NewThemeRef(theme.FluentLight())

darkMode := ui.Toggle(false).OnChange(func(on bool) {
    if on {
        themeRef.Set(theme.FluentDark())
    } else {
        themeRef.Set(theme.FluentLight())
    }
})

ui.Run("App", func() ui.View {
    return ui.VStack(
        ui.HStack(
            ui.Text("Dark mode"),
            ui.Spacer(),
            darkMode,
        ).Center(),
        ui.Divider(),
        // ... rest of UI
    ).Spacing(12)
}, ui.WithThemeRef(themeRef))

ui.RunWith("App", func(th *theme.Theme) ui.View {
    return ui.Text("Primary colored").Color(th.Palette.Primary)
})

var currentTheme = theme.FluentLight()

var themeToggle = widget.NewToggle(false).
    WithOnChange(func(dark bool) {
        if dark {
            currentTheme = theme.FluentDark()
        } else {
            currentTheme = theme.FluentLight()
        }
    })

func main() {
    myApp := app.New("Themed App")
    myApp.WithLayout(func(gtx layout.Context, th *theme.Theme) layout.Dimensions {
        myApp.Theme = currentTheme
        return myLayout(gtx, currentTheme)
    }).Run()
}

func MyTheme() *theme.Theme {
    th := theme.FluentLight()

    // Custom brand colors
    th.Palette.Primary = theme.NRGBA(0x67, 0x50, 0xA4, 0xFF)
    th.Palette.OnPrimary = theme.NRGBA(0xFF, 0xFF, 0xFF, 0xFF)
    th.Palette.Secondary = theme.NRGBA(0x62, 0x5B, 0x71, 0xFF)

    // Larger text
    th.Typo.BodyMedium.Size = 16

    // More rounded corners
    th.Corner.MD = 12

    return th
}

// Declarative:
ui.Run("App", build, ui.Theme(MyTheme()))

// Lower-level:
app.New("App").WithTheme(MyTheme()).Run()

fontData, _ := os.ReadFile("Inter-Regular.ttf")
faces, _ := opentype.ParseCollection(fontData)

// Add custom fonts with Go fonts as fallback
th := theme.FluentLight().WithFonts(faces...)

// Or use only custom fonts (no Go font fallback)
th := theme.FluentLight().WithFontsOnly(faces...)

// Or embedded fonts only (no system fonts either)
th := theme.FluentLight().WithEmbeddedFontsOnly(faces...)

// Create NRGBA color
theme.NRGBA(0xFF, 0x00, 0x78, 0xFF)

// Modify alpha channel
theme.WithAlpha(th.Palette.Primary, 128)  // 50% transparent

// Interpolate between colors
theme.Lerp(colorA, colorB, 0.5)           // Midpoint

import "github.com/amken3d/immygo/style"

// Float animator
anim := style.NewFloatAnimator(200*time.Millisecond, 0.0)
anim.SetTarget(1.0)
val := anim.Value()        // current interpolated value
if anim.Active() {
    gtx.Execute(op.InvalidateCmd{})
}

// Color animator
colorAnim := style.NewColorAnimator(200*time.Millisecond, startColor)
colorAnim.SetTarget(endColor)
col := colorAnim.Value()