This package is part of the SNAP suite.

SnapTheme

A toolset to abstract Colors, Fonts, Icons and Numbers of a multi-platform SwiftUI app. Define semantic attributes in a Theme and apply them to your views for a consistent UI with maintainability in mind.

Motivation

Consistency in look and feel is important. Especially for a growing app project, when you decide to tweak a few attributes or need adjustments to fit platform changes or design trends. Goal of SnapTheme is to define visual attributes in a single place, to allow: A consistent UI with simple adjustments and quick experiments, but strong maintainability.

Instead of defining design attributes all over the place, you register a semantic key, assign a definition and use it in your SwiftUI views. You can also define multiple Themes to let the user choose it's favorite.

Theme comes with:

• Base attributes (Color, Font, Icon, Number) and composed attributes (Surface, Background, TextSurface).
• A preset of common semantic definitions for these attributes (e.g. .textTitle, .textSubtitle) with platform specific default values.
• ViewModifier to apply them to your views.
• Wrapper of stock SwiftUI views to set attributes from Theme definitions (e.g. ThemeVStack(spacing:)).
• Convenience views for common layout and style tasks (e.g. ThemeScreen, ThemeElement).

The Theme is injected in the Environment to be available to ViewModifier and Views.

Fonts and Numbers are scaled by DynamicType by default. This brings some additional benefits:

• UI sizes (paddings, spacings, ...) defined by the Theme will scale with DynamicType.
• By adjusting the Themes scale factor, the whole UI can be zoomed by a simple value change.

How to use

The Theme comes with some presets and is easy to use and customize.

Define the Theme

Override preset attributes in a custom Theme:

let theme = Theme(
	colors: [
		.accentColorBase : .color(.purple)
	], 
	...
)

And/or define your own attributes:

extension Theme.ColorKey {
	static let exampleColor = Theme.ColorKey("exampleColor", default: .color(.purple))
}

Apply the Theme

contentView.theme(apply: theme)

Use the Theme

Text("Example").color(.exampleColor)

Definitions

ColorKey

Represent a semantic meaning of the color (.foreground, .background, .accent, .destructive). They do not describe the color or specific use case (.red, .buttonLabel).

SurfaceKey

A Surface represents a ShapeStyle, either a color, material or gradient.

FontKey

Represents a semantic meaning of text (.textTitle, .textSubtitle) and assigns a FontDefinition.

IconKey

Represents a semantic meaning of a visual indicator and assigns an image.

NumberKey

Represents a specific value. Scaled by dynamic type.

Key Assignments

TextSurfaceKey

Assigns a Surface to a font.

BackgroundKey

Defines the background of a semantic layout element (.screen, .content, .contentSecondary) by assigning a Surface and a highlight Surface.

SnapAppThemeDemo

A demo of the Theme in action is available at snap-app-theme-demo. It provides a reference for all preset attributes, demonstrates the default values and provides some configuration sets to change attributes in the app.

Elements of the Theme

ThemeKeys

Key and default value.

ThemeValues

Values registered for a ThemeKey.

Examples: BackgroundValue, ColorValue (TextSurface), FontValue, IconValue, NumberValue

ThemeModifier

Modifier using ThemeKeys to apply the configured values on a view.

Examples: .theme(background:), .theme(color:), .theme(text:), .theme(padding:)

LayoutElements

Generic container views used for layout. Basic building blocks of to build a screen.

Examples: ThemeScreen, ThemeHStack(spacing:), ThemeElement

Components

Views that show content and use ThemeKeys to configure style and layout.

Examples: ThemeLabel(icon:), ThemeCornerView(icon:), ThemeRectangle(cornerRadius:)

Container

Container use ThemeKeys to layout content.

Examples: ThemeCloseContainer, ThemeSectionHeaderContainer

Styles

Definitions of SwiftUI styles using ThemeKeys.

Examples: ThemeButtonStyle, ThemeLabelStyleTag