display-glasses-with-jetpack-compose-glimmer

Imported from android/skills (xr/display-glasses-with-jetpack-compose-glimmer/SKILL.md) via skills.sh. Install upstream with npx skills add android/skills --skill display-glasses-with-jetpack-compose-glimmer. Copyright stays with the author (Complete terms in LICENSE.txt).

Glossary

Prerequisites

• Mobile project must target compileSdk 37 or higher. If the compileSdk is lower than 37, increase the compileSdk to 37.
• Ensure you are using the latest library dependencies from Create your first activity for intelligent eyewear.

Core Constraints

• Don't: Use MaterialTheme or Material Components.
• Do: Use GlimmerTheme and Jetpack Compose Glimmer Components.
• Do: Use createGoogleSansFlexTypography() from androidx.xr.glimmer:glimmer-google-fonts as the Typography value for GlimmerTheme to ensure that consistent typography is applied throughout the components.

Limitations

• Specific hardware device models or their unique capabilities are not detailed.
• Elevation: Standard Material 3 shadow or elevation modifiers are not supported. You must use ShadowScope or Depth tokens from Jetpack Compose Glimmer.
• Minimum Size: The absolute minimum size for readable text is 18sp (0.6°). Anything smaller will fail legibility checks.
• Text Weight: Avoid "Thin" or "Hairline" weights; they cause shimmering and aliasing on additive AR lenses.

1. Set up dependencies

• Setup Projected Activity: First, you need to create a new projected activity for your app. If the project doesn't already have one, see Create your first activity for intelligent eyewear. Use references/projectedcontext-source.md to launch the Glasses Projected activity on the Projected Device. Ensure that you specify xr_projected for the android:requiredDisplayCategory attribute in app manifest to tell the system that this activity will use a projected context to access hardware from a connected device.
• Mobile App Integration: If the project contains an existing mobile app, you must create a new Glasses Activity dedicated to rendering Glimmer UI. For detailed configuration, heavily reference Create your first activity for intelligent eyewear. If there isn't already a method to launch the Glasses Activity, add a button to the existing mobile app UI labeled "Launch on Glasses" that uses ProjectedContext to launch the Glasses Activity on the glasses. Place the 'Launch on Glasses' button as a screen-level FloatingActionButton, in the TopAppBar, or in the top navigation bar to ensure users discover the projection capability. If the glasses aren't connected, disable the button. Don't launch the Glasses Activity on the phone, only on the display glasses. If it makes sense to automatically launch the Glasses Activity without an explicit launch button, then do so.
• UI Library: Identify if the project has the androidx.xr.glimmer:glimmer library, if not it must be added to the project. See Declaring Jetpack Compose Glimmer Dependencies to fetch the latest dependency version.
• Theming: All Glimmer components must be wrapped within the GlimmerTheme composable to ensure correct token resolution.
• Mandatory black background: Display glasses use additive displays. Any non-black color in the background blocks the real world. You must always set a pure black background (Modifier.background(Color.Black)) on the root container of your Projected Activity.
• Font: The default font is Google Sans Flex. Use androidx.xr.glimmer.googlefonts library with the default type styles unless otherwise specified. Use createGoogleSansFlexTypography to create a Typography instance with the Google Sans Flex configuration. Provide this Typography instance as normal through GlimmerTheme. Use references/glimmersansflextypography-source.md for configuration.
• Hardware Capabilities: Different types of intelligent eyewear devices have different capabilities. To check for these at runtime, see the Check device capabilities at runtime for intelligent eyewear.
• Hardware Permissions: To request hardware permissions like the microphone and camera, see the Request hardware permissions for intelligent eyewear.
• Hardware Access: To use the glasses camera, sensors, or access the phone's hardware, see the Use a projected context to access hardware on intelligent eyewear.

2. Minimize and translate the UI

• For display glasses, build UI using components from the Jetpack Compose Glimmer framework.
• Use depth to communicate element priority and hierarchy.
• Design from the bottom up, trying to minimize how much of the real world you cover. Always bottom align UI to the glasses display.
• One Thing at a Time: Prioritize the user's awareness of the real world. Show only one primary piece of information at a time (for example, using a Stack) to minimize obstruction of the user's field of view. Avoid multiple simultaneous cards.
• Color Contrast: Ensure at least a 70% tone difference between foreground and background using the HCT color space. For calculation metrics, use references/material-hct-source.md.

3. Map input controls

• Map app interactions, such as tap and swipe, to the available hardware controls on the glasses, such as the touchpad.
• Inputs are one-dimensional; users must make one control input at a time.
• Avoid nesting scrolling controls.
• Jetpack Compose Glimmer components are designed to work with standard input methods, such as a tap or swipe on the glasses' touchpad.
• Use System Back to dismiss temporary states or detailed views.
• To add input, focus, tap, swipe to your Glasses UI, follow Focus in Jetpack Compose Glimmer.
  • For a detailed breakdown of hardware inputs, see Hardware Controls for display glasses

4. Build with Jetpack Compose Glimmer

Jetpack Compose Glimmer is the UI toolkit for building augmented experiences on display glasses.

Key Features

• Glimmer Theming: A simplified glasses-specific theme for optimal visibility.
• Pre-compatible Input: Supports tap and swipe by default.
• Pre-built Components: Provides optimized composables like Card, ListItem, Button, etc.

Focus Management in Glimmer

• Jetpack Compose Glimmer uses a one-dimensional focus search.
• Focus movement is continuous for scrollable containers and discrete for elements like a row of buttons.
• To enable the system to automatically set initial focus, you must set the isInitialFocusOnFocusableAvailable flag to true in your activity's onCreate method. For more information on how to implement, see Focus in Jetpack Compose Glimmer.

Implementing Glimmer Styles

Glimmer styles are accessed through the GlimmerTheme object. Use references/glimmertheme-source.md for reference.

Typography Scale (Google Sans Flex)

Strict default: When creating Glimmer UI you must use Google Sans Flex unless a custom brand typeface is explicitly specified. Variable Font Settings: As Google Sans Flex is a variable font, you must configure the following axes:

• Roundness (ROND): Always set to 100f for the signature rounded appearance.
• Width (wdth): Set to 100f.
• Optical Size (opsz): Set to 9f.
• Weight (wght): Use specific values for different roles (Title: 725f, Body: 520f, Caption: 650f).

Depth Levels

Simulate depth on display glasses using shadows to establish a sense of hierarchy through varying levels of emphasis. The Jetpack Compose Glimmer controls use DepthEffect with 5 preset DepthEffectLevels. Use references/deptheffect-source.md and references/deptheffectlevels-source.md for reference.

Some examples:

Implementing Jetpack Compose Glimmer Components

Cards

Cards are a fundamental surface-based container in Glimmer used to group related content, such as text, images, icons and actions into a single focal point. They establish a clear depth plane (Z-axis) in the Glasses environment, providing a stable background for text, images, and icons. Never embed a card within a List Item.

Core Implementation Logic

• Surface Hierarchy: Cards are designed to sit on a base surface or within a list. They provide an automatic visual feedback when focused if an onClick lambda is provided.
• Interactivity:
  • IF the entire Card serves as a single trigger (e.g., a media item or a setting): THEN provide an onClick lambda to enable focus effects.
  • ELSE: Leave onClick as null if the Card contains multiple internal interactive elements (like separate buttons or switches) to avoid focus contention.

Technical Documentation Links

If you are creating a Glimmer Card component, read the:

• Developer Guidance: Jetpack Compose Glimmer: Cards
• API Source Code: Use references/card-source.md.
• Implementation Samples: Use references/card-samples-source.md. (Basic and Interactive Card usage)

Buttons

Buttons are the primary triggers for discrete actions in Glimmer. They are specifically optimized for the display glasses focus model, where a focus highlight is added when focus is moved to the button using the touchpad or other methods.

Core Implementation Logic

• There are two types of buttons to choose from in Glimmer:
  • Standard buttons (Required text label with optional leading or trailing icons). Use this when there is more space in the UI, or when the meaning of the button isn't clear without text.
  • Icon buttons (icon only). Only use icon buttons when the icon is clearly understandable.
• Both icon and standard buttons have default and toggle variants:
  • Default (use for single actions like "buy" or "navigate")
  • Toggle (use for things with selected states like mute buttons)

Technical Documentation Links

If you are creating a Glimmer Button component, read the:

• Developer Guidance: Jetpack Compose Glimmer: Buttons
• API Source Code: Use references/button-source.md.
• Implementation Samples: Use references/button-samples-source.md.

Title Chips

Chips are a pill-shaped, specialized labeling component designed to sit above a Card or a group of content to provide a title. Use title chips to display concise information like a short title, a name, or a status.

Guidelines and usage

• Spatial Spacing : When using a standalone TitleChip preceding content, you must use TitleChipDefaults.AssociatedContentSpacing (8.dp) to maintain the visual hierarchy.
• Interactivity: Title chips are purely for informational purposes, they cannot be targeted or activated for navigation.
• Layout Always center text in a title chip. Never let the title chip go to two lines, and truncate extra words. Keep the label to three words or less.

Technical Documentation Links

If you are creating a Glimmer Title Chip component, read the:

• Developer Guidance: Jetpack Compose Glimmer: Title Chips
• API Source Code: Use references/titlechip-source.md.
• Implementation Samples: Use references/titlechip-samples-source.md. (Title Chips above group content)

Icons

Icons are visual symbols used to represent concepts, actions, or status in a concise way. In Glimmer, icons and icon buttons are optimized for the XR environment, providing clear visibility on additive displays and gaze-responsive feedback for interactive elements.

Guidelines and usage

• Sizing: Use predefined IconSizes (e.g., Standard, Large) to ensure icons remain legible and meet the minimum touch target requirements for the XR environment.
• Interactivity:
  • If an icon serves as a trigger: Then you must use an IconButton to provide the automatic visual feedback and required tap-target padding.
  • ELSE: Use a standalone Icon for non-interactive indicators or status symbols.
• Contrast: NEVER use pure black (#000000) for icon tints; always use themed colors or standard Glimmer content colors to ensure the icon is visible against dark or real-world backgrounds.
• Icon Library The default icon library is Material Symbols with 600 weight, Rounded, Unfilled, unless otherwise specified.

Technical Documentation Links

If you are creating a Glimmer Icon component, read the:

• Developer Guidance: Jetpack Compose Glimmer: Icons
• API Source Code (Icon): Use references/icon-source.md.
• API Source Code (IconButton): Use references/iconbutton-source.md.
• API Source Code (IconSizes): Use references/iconsizes-source.md.

Lists

Lists are containers that allow you to navigate between and see multiple items on glasses. If your use case works with only seeing one item in the list at a time, use a Glimmer Stack. Use lists with a Title Chip when the list items are similar in type. Also use a Glimmer Stack if the items are of different types.

Guidelines and usage

• ListItem Slots: Use the ListItem composable for rows. It provides predefined slots. Use references/listitem-source.md for reference.
• Visual Consistency: When building lists of similar items, always use a consistent background color (typically GlimmerTheme.colors.surface) and corner radius (standard 36.dp) for every item. Don't vary these unless you are visually grouping different types of content.
• Integrated Title Chips: Glimmer Lists support integrated title chips. IF you need a section header within a list: THEN enable the integrated title chip rather than adding a standalone TitleChip to maintain spatial consistency.
• Vertical Arrangement: ALWAYS use verticalArrangement = Arrangement.spacedBy(20.dp) for GlimmerLazyColumn to ensure visual separation between items on the glasses display.
• Be sure to use the default 20 dp spacing between list items unless otherwise specified.

Technical Documentation Links

If you are creating a Glimmer List component, read the:

• API Source Code (List): Use references/list-source.md.
• API Source Code (ListItem): Use references/listitem-source.md.
• API Source Code (GlimmerLazyListState): Use references/liststate-source.md.

Stacks

A stack is a collapsed list that only displays one piece of content at a time, in a stacked visual, such as a card. If it is useful to show more than one item at a time, use the Glimmer List control. Don't use a title chip with a stack. If the items are of different types use a stack to show them. If the items are of the same type, use a list.

Guidelines and usage

Layout tips

• Stacks accept variable height items.
• Align your stack control with the bottom of the display.
• The stack control must be 66 dp taller than the tallest item in the stack, allowing room for the scrim and minimizing movement when navigating between items.
• Clipping and Layering: To ensure that items behind the top item are correctly clipped and hidden, you must apply the .itemDecoration(CardDefaults.shape) modifier to the Card (or relevant container) inside every item block.
• Depth Shadows: To maintain spatial separation and element priority, utilize Glimmer's ShadowScope, DepthEffect, or prescribed DepthEffectLevels for depth plane scaling.

Technical Documentation Links

If you are creating a Glimmer Stack component, read the:

• API Source Code (Stack): Use references/stack-source.md.
• API Source Code (StackState): Use references/stackstate-source.md.
• API Source Code (StackItemScope): Use references/stackitemscope-source.md.

Text

In Jetpack Compose Glimmer, the Text component builds off the Compose text component, and lets you set various text properties. Be sure to choose a style from the GlimmerTheme for your text. Modify the theme for your application if you want custom typography.

Essential Constraint: Glimmer Text versus Material Text

On transparent Display Glasses (additive displays), standard Material Text resolves to dark foreground tokens which render as transparent and invisible. Glimmer Text intelligently manages theme color matching. When no manual color override is specified, Glimmer Text automatically defaults to the content color provided by the nearest Glimmer surface.

• Don't: Use Material Text
• Do: Use Glimmer Text

Surface

Surface is a fundamental building block in Glimmer. Use references/surface-source.md for reference.

A surface represents a distinct visual area or 'physical' boundary for components such as buttons and cards. Use it if you need to build a custom component.

5. Integrate with system UI

• For a detailed breakdown of notifications on intelligent eyewear, see Understand notification behavior for intelligent eyewear and learn how to Start a glasses activity on display glasses from a notification.