Clay

Clay (short for C Layout) is a high performance 2D UI layout library.

Major Features

• Microsecond layout performance
• Flex-box like layout model for complex, responsive layouts including text wrapping, scrolling containers and aspect ratio scaling
• Single ~2k LOC clay.h file with zero dependencies (including no standard library)
• Wasm support: compile with clang to a 15kb uncompressed .wasm file for use in the browser
• Static arena based memory use with no malloc / free, and low total memory overhead (e.g. ~3.5mb for 8192 layout elements).
• React-like nested declarative syntax
• Renderer agnostic: outputs a sorted list of rendering primitives that can be easily composited in any 3D engine, and even compiled to HTML (examples provided)

Take a look at the clay website for an example of clay compiled to wasm and running in the browser, or others in the examples directory.

An example GUI application built with clay

Quick Start

1. Download or clone clay.h and include it after defining CLAY_IMPLEMENTATION in one file.

// Must be defined in one file, _before_ #include "clay.h"
#define CLAY_IMPLEMENTATION
#include "clay.h"

2. Ask clay for how much static memory it needs using Clay_MinMemorySize(), create an Arena for it to use with Clay_CreateArenaWithCapacityAndMemory(size, void *memory), and initialize it with Clay_Initialize(arena, dimensions).

// Note: malloc is only used here as an example, any allocator that provides
// a pointer to addressable memory of at least totalMemorySize will work
uint64_t totalMemorySize = Clay_MinMemorySize();
Clay_Arena arena = Clay_CreateArenaWithCapacityAndMemory(totalMemorySize, malloc(totalMemorySize));
Clay_Initialize(arena, (Clay_Dimensions) { screenWidth, screenHeight });

3. Provide a MeasureText(text, config) function pointer with Clay_SetMeasureTextFunction(function) so that clay can measure and wrap text.

// Example measure text function
static inline Clay_Dimensions MeasureText(Clay_String *text, Clay_TextElementConfig *config) {
    // Clay_TextElementConfig contains members such as fontId, fontSize, letterSpacing etc
    // Note: Clay_String->chars is not guaranteed to be null terminated
}

// Tell clay how to measure text
Clay_SetMeasureTextFunction(MeasureText);

4. Optional - Call Clay_SetLayoutDimensions(dimensions) if the window size of your application has changed.

// Update internal layout dimensions
Clay_SetLayoutDimensions((Clay_Dimensions) { screenWidth, screenHeight });

5. Optional - Call Clay_SetPointerState(pointerPosition, isPointerDown) if you want to use mouse interactions.

// Update internal pointer position for handling mouseover / click / touch events
Clay_SetPointerState((Clay_Vector2) { mousePositionX, mousePositionY }, isMouseDown);

6. Optional - Call Clay_UpdateScrollContainers(enableDragScrolling, scrollDelta, deltaTime) if you want to use clay's built in scrolling containers.

// Update internal pointer position for handling mouseover / click / touch events
Clay_UpdateScrollContainers(true, (Clay_Vector2) { mouseWheelX, mouseWheelY }, deltaTime);

7. Call Clay_BeginLayout() and declare your layout using the provided macros.

const Clay_Color COLOR_LIGHT = (Clay_Color) {224, 215, 210, 255};
const Clay_Color COLOR_RED = (Clay_Color) {168, 66, 28, 255};
const Clay_Color COLOR_ORANGE = (Clay_Color) {225, 138, 50, 255};

// Layout config is just a struct that can be declared statically, or inline
Clay_LayoutConfig sidebarItemLayout = (Clay_LayoutConfig) {
    .sizing = { .width = CLAY_SIZING_GROW(), .height = CLAY_SIZING_FIXED(50) },
};

// Re-useable components are just normal functions
void SidebarItemComponent() {
    CLAY(CLAY_LAYOUT(sidebarItemLayout), CLAY_RECTANGLE({ .color = COLOR_ORANGE })) {}
}

// An example function to begin the "root" of your layout tree
Clay_RenderCommandArray CreateLayout() {
    Clay_BeginLayout();

    // An example of laying out a UI with a fixed width sidebar and flexible width main content
    CLAY(CLAY_ID("OuterContainer"), CLAY_LAYOUT({ .sizing = {CLAY_SIZING_GROW(), CLAY_SIZING_GROW()}, .padding = {16, 16}, .childGap = 16 }), CLAY_RECTANGLE({ .color = {250,250,255,255} })) {
        CLAY(CLAY_ID("SideBar"),
            CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_FIXED(300), .height = CLAY_SIZING_GROW() }, .padding = {16, 16}, .childGap = 16 }),
            CLAY_RECTANGLE({ .color = COLOR_LIGHT })
        ) {
            CLAY(CLAY_ID("ProfilePictureOuter"), CLAY_LAYOUT({ .sizing = { .width = CLAY_SIZING_GROW() }, .padding = {16, 16}, .childGap = 16, .childAlignment = { .y = CLAY_ALIGN_Y_CENTER }), CLAY_RECTANGLE({ .color = COLOR_RED })) {
                CLAY(CLAY_ID("ProfilePicture"), CLAY_LAYOUT({ .sizing = { .width = CLAY_SIZING_FIXED(60), .height = CLAY_SIZING_FIXED(60) }}), CLAY_IMAGE({ .imageData = &profilePicture, .height = 60, .width = 60 })) {}
                CLAY_TEXT(CLAY_STRING("Clay - UI Library"), CLAY_TEXT_CONFIG({ .fontSize = 24, .textColor = {255, 255, 255, 255} }));
            }

            // Standard C code like loops etc work inside components
            for (int i = 0; i < 5; i++) {
                SidebarItemComponent();
            }
        }

        CLAY(CLAY_ID("MainContent"), CLAY_LAYOUT({ .sizing = { .width = CLAY_SIZING_GROW(), .height = CLAY_SIZING_GROW() }}), CLAY_RECTANGLE({ .color = COLOR_LIGHT })) {}
    }
    // ...
});

8. Call Clay_EndLayout() and process the resulting Clay_RenderCommandArray in your choice of renderer.

Clay_RenderCommandArray renderCommands = Clay_EndLayout();

for (int i = 0; i < renderCommands.length; i++) {
    Clay_RenderCommand *renderCommand = &renderCommands.internalArray[i];
    
    switch (renderCommand->commandType) {
        case CLAY_RENDER_COMMAND_TYPE_RECTANGLE: {
            DrawRectangle(
                renderCommand->boundingBox,
                renderCommand->config.rectangleElementConfig->color);
        }
        // ... Implement handling of other command types
    }
}

The above example, rendered correctly will look something like the following:

In summary, the general order of steps is:

1. Clay_SetLayoutDimensions(dimensions)
2. Clay_SetPointerState(pointerPosition, isPointerDown)
3. Clay_UpdateScrollContainers(enableDragScrolling, scrollDelta, deltaTime)
4. Clay_BeginLayout()
5. Declare your layout with the provided Element Macros
6. Clay_EndLayout()
7. Render the results using the outputted Clay_RenderCommandArray

For help starting out or to discuss clay, considering joining the discord server.

High Level Documentation

Building UI Hierarchies

Clay UIs are built using the C macro CLAY(). This macro creates a new empty element in the UI hierarchy, and supports modular customisation of layout, styling and functionality. The CLAY() macro can also be nested, similar to other declarative UI systems like HTML.

Child elements are added by opening a block: {} after calling the CLAY() macro (exactly like you would with an if statement or for loop), and declaring child components inside the braces.

// Parent element with 8px of padding
CLAY(CLAY_LAYOUT({ .padding = 8 })) {
    // Child element 1
    CLAY_TEXT(CLAY_STRING("Hello World"), CLAY_TEXT_CONFIG({ .fontSize = 16 }));
    // Child element 2 with red background
    CLAY(CLAY_RECTANGLE({ .color = COLOR_RED })) {
        // etc
    }
}

However, unlike HTML and other declarative DSLs, these macros are just C. As a result, you can use arbitrary C code such as loops, functions and conditions inside your layout declaration code:

// Re-usable "components" are just functions that declare more UI
void ButtonComponent(Clay_String buttonText) {
    // Red box button with 8px of padding
    CLAY(CLAY_LAYOUT({ .padding = { 8, 8 }}), CLAY_RECTANGLE({ .color = COLOR_RED })) {
        CLAY_TEXT(buttonText, textConfig);
    }
}

// Parent element
CLAY(CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM })) {
    // Render a bunch of text elements
    for (int i = 0; i < textArray.length; i++) {
        CLAY_TEXT(textArray.elements[i], textConfig);
    }
    // Only render this element if we're on a mobile screen
    if (isMobileScreen) {
        CLAY() {
            // etc
        }
    }
    // Re-usable components
    ButtonComponent(CLAY_STRING("Click me!"));
    ButtonComponent(CLAY_STRING("No, click me!"));
});

Configuring Layout and Styling UI Elements

The layout of clay elements is configured with the CLAY_LAYOUT() macro.

CLAY(CLAY_LAYOUT({ .padding = {.x = 8, .y = 8}, .layoutDirection = CLAY_TOP_TO_BOTTOM })) {
    // Children are 8px inset into parent, and laid out top to bottom
}

This macro isn't magic - all it's doing is wrapping the standard designated initializer syntax and adding the result to an internal array. e.g. (Clay_LayoutConfig) { .padding = { .x = 8, .y = 8 } ....

See the Clay_LayoutConfig API for the full list of options.

A Clay_LayoutConfig struct can be defined in file scope or elsewhere, and reused.

// Define a style in the global / file scope
Clay_LayoutConfig reusableStyle = (Clay_LayoutConfig) { .backgroundColor = {120, 120, 120, 255} };

CLAY(CLAY_LAYOUT(reusableStyle)) {
    // ...
}

Element IDs

Clay elements can optionally be tagged with a unique identifier using CLAY_ID().

// Will always produce the same ID from the same input string
CLAY(CLAY_ID("OuterContainer"), style) {}

Element IDs have two main use cases. Firstly, tagging an element with an ID allows you to query information about the element later, such as its mouseover state or dimensions.

Secondly, IDs are visually useful when attempting to read and modify UI code, as well as when using the built-in debug tools.

To avoid having to construct dynamic strings at runtime to differentiate ids in loops, clay provides the CLAY_IDI(string, index) macro to generate different ids from a single input string. Think of IDI as "ID + Index"

// This is the equivalent of calling CLAY_ID("Item0"), CLAY_ID("Item1") etc
for (int index = 0; index < items.length; index++) {
    CLAY(CLAY_IDI("Item", index)) {}
}

This ID (or, if not provided, an auto generated ID) will be forwarded to the final Clay_RenderCommandArray for use in retained mode UIs. Using duplicate IDs may cause some functionality to misbehave (i.e. if you're trying to attach a floating container to a specific element with ID that is duplicated, it may not attach to the one you expect)

Mouse, Touch and Pointer Interactions

Clay provides several functions for handling mouse and pointer interactions.

All pointer interactions depend on the function void Clay_SetPointerState(Clay_Vector2 position) being called after each mouse position update and before any other clay functions.

During UI declaration

The function bool Clay_Hovered() can be called during element construction or in the body of an element, and returns true if the mouse / pointer is over the currently open element.

// An orange button that turns blue when hovered
CLAY(CLAY_RECTANGLE(.color = Clay_Hovered() ? COLOR_BLUE : COLOR_ORANGE)) {
    bool buttonHovered = Clay_Hovered();
    CLAY_TEXT(buttonHovered ? CLAY_STRING("Hovered") : CLAY_STRING("Hover me!"), headerTextConfig);
}

The function void Clay_OnHover() allows you to attach a function pointer to the currently open element, which will be called if the mouse / pointer is over the element.

void HandleButtonInteraction(Clay_ElementId elementId, Clay_PointerData pointerInfo, intptr_t userData) {
    ButtonData *buttonData = (ButtonData *)userData;
    // Pointer state allows you to detect mouse down / hold / release
    if (pointerInfo.state == CLAY_POINTER_DATA_PRESSED_THIS_FRAME) {
        // Do some click handling
        NavigateTo(buttonData->link);
    }
}

ButtonData linkButton = (ButtonData) { .link = "https://github.com/nicbarker/clay" };

// HandleButtonInteraction will be called for each frame the mouse / pointer / touch is inside the button boundaries
CLAY(CLAY_LAYOUT({ .padding = { 8, 8 }}), Clay_OnHover(HandleButtonInteraction, &linkButton)) {
    CLAY_TEXT(CLAY_STRING("Button"), &headerTextConfig);
}

Before / After UI declaration

If you want to query mouse / pointer overlaps outside layout declarations, you can use the function bool Clay_PointerOver(Clay_ElementId id), which takes an element id and returns a bool representing whether the current pointer position is within its bounding box.

// Reminder: Clay_SetPointerState must be called before functions that rely on pointer position otherwise it will have no effect
Clay_Vector2 mousePosition = { x, y };
Clay_SetPointerState(mousePosition);
// ...
// If profile picture was clicked
if (mouseButtonDown(0) && Clay_PointerOver(Clay_GetElementId("ProfilePicture"))) {
    // Handle profile picture clicked
}

Note that the bounding box queried by Clay_PointerOver is from the last frame. This generally shouldn't make a difference except in the case of animations that move at high speed. If this is an issue for you, performing layout twice per frame with the same data will give you the correct interaction the second time.

Scrolling Elements

Elements are configured as scrollable with the CLAY_SCROLL macro. To make scroll containers respond to mouse wheel and scroll events, two functions need to be called before BeginLayout():

Clay_Vector2 mousePosition = { x, y };
// Reminder: Clay_SetPointerState must be called before Clay_UpdateScrollContainers otherwise it will have no effect
Clay_SetPointerState(mousePosition);
// Clay_UpdateScrollContainers needs to be called before Clay_BeginLayout for the position to avoid a 1 frame delay
Clay_UpdateScrollContainers(
    true, // Enable drag scrolling
    scrollDelta, // Clay_Vector2 scrollwheel / trackpad scroll x and y delta this frame
    float deltaTime, // Time since last frame in seconds as a float e.g. 8ms is 0.008f
);
// ...

More specific details can be found in the full Scroll API.

Floating Elements ("Absolute" Positioning)

All standard elements in clay are laid out on top of, and within their parent, positioned according to their parent's layout rules, and affect the positioning and sizing of siblings.

"Floating" is configured with the CLAY_FLOATING() macro. Floating elements don't affect the parent they are defined in, or the position of their siblings. They also have a z-index, and as a result can intersect and render over the top of other elements.

A classic example use case for floating elements is tooltips and modals.

// The two text elements will be laid out top to bottom, and the floating container
// will be attached to "Outer"
CLAY(CLAY_ID("Outer"), CLAY_LAYOUT({ .layoutDirection = TOP_TO_BOTTOM })) {
    CLAY_TEXT(CLAY_ID("Button"), text, &headerTextConfig);
    CLAY(CLAY_ID("Tooltip"), CLAY_FLOATING()) {}
    CLAY_TEXT(CLAY_ID("Button"), text, &headerTextConfig);
}

More specific details can be found in the full Floating API.

Laying Out Your Own Custom Elements

Clay only supports a simple set of UI element primitives, such as rectangles, text and images. Clay provides a singular API for layout out custom elements:

// Extend CLAY_CUSTOM_ELEMENT_CONFIG with your custom data
#define CLAY_EXTEND_CONFIG_CUSTOM struct t_CustomElementData customData;
// Extensions need to happen _before_ the clay include
#include "clay.h"

enum CustomElementType {
    CUSTOM_ELEMENT_TYPE_MODEL,
    CUSTOM_ELEMENT_TYPE_VIDEO
};

// A rough example of how you could handle laying out 3d models in your UI
typedef struct t_CustomElementData {
    CustomElementType type;
    union {
        Model model;
        Video video;
        // ...
    };
} CustomElementData;

Model myModel = Load3DModel(filePath);
CustomElement modelElement = (CustomElement) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel }
// ...
CLAY() {
    // This config is type safe and contains the CustomElementData struct
    CLAY(CLAY_CUSTOM_ELEMENT({ .customData = { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel } })) {}
}

// Later during your rendering
switch (renderCommand->commandType) {
    // ...
    case CLAY_RENDER_COMMAND_TYPE_CUSTOM: {
        // Your extended struct is passed through
        CustomElementData *customElement = renderCommand->config.customElementConfig->customData;
        if (!customElement) continue;
        switch (customElement->type) {
            case CUSTOM_ELEMENT_TYPE_MODEL: {
                // Render your 3d model here
                break;
            }
            case CUSTOM_ELEMENT_TYPE_VIDEO: {
                // Render your video here
                break;
            }
            // ...
        }
        break;
    }
}

More specific details can be found in the full Custom Element API.

Retained Mode Rendering

Clay was originally designed for Immediate Mode rendering - where the entire UI is redrawn every frame. This may not be possible with your platform, renderer design or performance constraints.

There are some general techniques that can be used to integrate clay into a retained mode rendering system:

• Clay_RenderCommand includes the uint32_t id that was used to declare the element. If unique ids are used, these can be mapped to persistent graphics objects across multiple frames / layouts.
• Render commands are culled automatically to only currently visible elements, and Clay_RenderCommand is a small enough struct that you can simply compare the memory of two render commands with matching IDs to determine if the element is "dirty" and needs to be re-rendered or updated.

For a worked example, see the provided HTML renderer. This renderer converts clay layouts into persistent HTML documents with minimal changes per frame.

Visibility Culling

Clay provides a built-in visibility-culling mechanism that is enabled by default. It will only output render commands for elements that are visible - that is, at least one pixel of their bounding box is inside the viewport.

This culling mechanism can be disabled via the use of the #define CLAY_DISABLE_CULLING directive. See Preprocessor Directives for more information.

Preprocessor Directives

Clay supports C preprocessor directives to modulate functionality at compile time. These can be set either in code using #define CLAY_DISABLE_CULLING or on the command line when compiling using the appropriate compiler specific arguments, e.g. clang -DCLAY_DISABLE_CULLING main.c ...

The supported directives are:

• CLAY_MAX_ELEMENT_COUNT - Controls the maximum number of clay elements that memory is pre-allocated for. Defaults to 8192, which should be more than enough for the majority of use cases. Napkin math is ~450 bytes of memory overhead per element (8192 elements is ~3.5mb of memory)
• CLAY_DISABLE_CULLING - Disables Visibility Culling of render commands.
• CLAY_WASM - Required when targeting Web Assembly.
• CLAY_OVERFLOW_TRAP - By default, clay will continue to allow function calls without crashing even when it exhausts all its available pre-allocated memory. This can produce erroneous layout results that are difficult to interpret. If CLAY_OVERFLOW_TRAP is defined, clay will raise a SIGTRAP signal that will be caught by your debugger. Relies on signal.h being available in your environment.
• CLAY_DEBUG - Used for debugging clay's internal implementation. Useful if you want to modify or debug clay, or learn how things work. It enables a number of debug features such as preserving source strings for hash IDs to make debugging easier.
• CLAY_EXTEND_CONFIG_RECTANGLE - Provide additional struct members to CLAY_RECTANGLE that will be passed through with output render commands.
• CLAY_EXTEND_CONFIG_TEXT - Provide additional struct members to CLAY_TEXT_CONFIG that will be passed through with output render commands.
• CLAY_EXTEND_CONFIG_IMAGE - Provide additional struct members to CLAY_IMAGE_CONFIG that will be passed through with output render commands.
• CLAY_EXTEND_CONFIG_CUSTOM - Provide additional struct members to CLAY_IMAGE_CONFIG that will be passed through with output render commands.

Bindings for non C

Clay is usable out of the box as a .h include in both C99 and C++20 with designated initializer support. There are also supported bindings for other languages, including:

• Odin Bindings

Unfortunately clay does not support Microsoft C11 or C17 via MSVC at this time.

Debug Tools

Clay includes built-in UI debugging tools, similar to the "inspector" in browsers such as Chrome or Firefox. These tools are included in clay.h, and work by injecting additional render commands into the output Clay_RenderCommandArray.

As long as the renderer that you're using works correctly, no additional setup or configuration is required to use the debug tools.

To enable the debug tools, use the function Clay_SetDebugModeEnabled(bool enabled). This boolean is persistent and does not need to be set every frame.

The debug tooling by default will render as a panel to the right side of the screen, compressing your layout by its width. The default width is 400 and is currently configurable via the direct mutation of the internal variable Clay__debugViewWidth, however this is an internal API and is potentially subject to change.

The official Clay website with debug tooling visible

API

Naming Conventions

• "CAPITAL_LETTERS()" are used for macros.
• "Clay__" ("Clay" followed by double underscore) is used for internal functions that are not intended for use and are subject to change.
• "Clay_" ("Clay" followed by single underscore) is used for external functions that can be called by the user.

Public Functions

Lifecycle for public functions

At startup / initialization time, run once Clay_MinMemorySize -> Clay_CreateArenaWithCapacityAndMemory -> Clay_SetMeasureTextFunction -> Clay_Initialize

Each Frame Clay_SetLayoutDimensions -> Clay_SetPointerState -> Clay_UpdateScrollContainers -> Clay_BeginLayout -> CLAY() etc... -> Clay_EndLayout

Clay_MinMemorySize

uint32_t Clay_MinMemorySize()

Returns the minimum amount of memory in bytes that clay needs to accomodate the current CLAY_MAX_ELEMENT_COUNT.

Clay_CreateArenaWithCapacityAndMemory

Clay_Arena Clay_CreateArenaWithCapacityAndMemory(uint32_t capacity, void *offset)

Creates a Clay_Arena struct with the given capacity and base memory pointer, which can be passed to Clay_Initialize.

Clay_SetMeasureTextFunction

void Clay_SetMeasureTextFunction(Clay_Dimensions (*measureTextFunction)(Clay_String *text, Clay_TextElementConfig *config))

Takes a pointer to a function that can be used to measure the width, height dimensions of a string. Used by clay during layout to determine CLAY_TEXT element sizing and wrapping.

Note 1: This string is not guaranteed to be null terminated. Clay saves significant performance overhead by using slices when wrapping text instead of having to clone new null terminated strings. If your renderer does not support ptr, length style strings (e.g. Raylib), you will need to clone this to a new C string before rendering.

Note 2: It is essential that this function is as fast as possible. For text heavy use-cases this function is called many times, and despite the fact that clay caches text measurements internally, it can easily become the dominant overall layout cost if the provided function is slow. This is on the hot path!

Clay_Initialize

void Clay_Initialize(Clay_Arena arena, Clay_Dimensions layoutDimensions)

Initializes the internal memory mapping, and sets the internal dimensions for layout.

Clay_SetLayoutDimensions

void Clay_SetLayoutDimensions(Clay_Dimensions dimensions)

Sets the internal layout dimensions. Cheap enough to be called every frame with your screen dimensions to automatically respond to window resizing, etc.

Clay_SetPointerState

void Clay_SetPointerState(Clay_Vector2 position, bool isPointerDown)

Sets the internal pointer position and state (i.e. current mouse / touch position) and recalculates overlap info, which is used for mouseover / click calculation (via Clay_PointerOver and updating scroll containers with Clay_UpdateScrollContainers. isPointerDown should represent the current state this frame, e.g. it should be true for the entire duration the left mouse button is held down. Clay has internal handling for detecting click / touch start & end.

Clay_UpdateScrollContainers

void Clay_UpdateScrollContainers(bool enableDragScrolling, Clay_Vector2 scrollDelta, float deltaTime)

This function handles scrolling of containers. It responds to both scrollDelta, which represents mouse wheel or trackpad scrolling this frame, as well as "touch scrolling" on mobile devices, or "drag scrolling" with a mouse or similar device.

Touch / drag scrolling only occurs if the enableDragScrolling parameter is true, and Clay_SetPointerState has been called this frame. As a result, you can simply always call it with false as the first argument if you want to disable touch scrolling.

deltaTime is the time in seconds since the last frame (e.g. 0.016 is 16 milliseconds), and is used to normalize & smooth scrolling across different refresh rates.

Clay_BeginLayout

void Clay_BeginLayout()

Prepares clay to calculate a new layout. Called each frame / layout before any of the Element Macros.

Clay_EndLayout

Clay_RenderCommandArray Clay_EndLayout()

Ends declaration of element macros and calculates the results of the current layout. Renders a Clay_RenderCommandArray containing the results of the layout calculation.

Clay_Hovered

bool Clay_Hovered()

Called during layout declaration, and returns true if the pointer position previously set with Clay_SetPointerState is inside the bounding box of the currently open element. Note: this is based on the element's position from the last frame.

Clay_OnHover

void Clay_OnHover(void (*onHoverFunction)(Clay_ElementId elementId, Clay_PointerData pointerData, intptr_t userData), intptr_t userData)

Called during layout declaration, this function allows you to attach a function pointer to the currently open element that will be called once per layout if the pointer position previously set with Clay_SetPointerState is inside the bounding box of the currently open element. See Clay_PointerData for more information on the pointerData argument.

void HandleButtonInteraction(Clay_ElementId elementId, Clay_PointerData pointerData, intptr_t userData) {
    ButtonData *buttonData = (ButtonData *)userData;
    // Pointer state allows you to detect mouse down / hold / release
    if (pointerData.state == CLAY_POINTER_DATA_PRESSED_THIS_FRAME) {
        // Do some click handling
        NavigateTo(buttonData->link);
    }
}

ButtonData linkButton = (ButtonData) { .link = "https://github.com/nicbarker/clay" };

// HandleButtonInteraction will be called for each frame the mouse / pointer / touch is inside the button boundaries
CLAY(CLAY_LAYOUT({ .padding = { 8, 8 }}), Clay_OnHover(HandleButtonInteraction, &buttonData)) {
    CLAY_TEXT(CLAY_STRING("Button"), &headerTextConfig);
}

Clay_PointerOver

bool Clay_PointerOver(Clay_ElementId id)

Returns true if the pointer position previously set with Clay_SetPointerState is inside the bounding box of the layout element with the provided id. Note: this is based on the element's position from the last frame. If frame-accurate pointer overlap detection is required, perhaps in the case of significant change in UI layout between frames, you can simply run your layout code twice that frame. The second call to Clay_PointerOver will be frame-accurate.

Clay_GetScrollContainerData

Clay_ScrollContainerData Clay_GetScrollContainerData(Clay_ElementId id)

Returns Clay_ScrollContainerData for the scroll container matching the provided ID. This function allows imperative manipulation of scroll position, allowing you to build things such as scroll bars, buttons that "jump" to somewhere in a scroll container, etc.

Clay_GetElementId

Clay_ElementId Clay_GetElementId(Clay_String idString)

Returns a Clay_ElementId for the provided id string, used for querying element info such as mouseover state, scroll container data, etc.

Element Macros

CLAY()

Usage

CLAY(...configuration) { ...children }

Lifecycle

Clay_BeginLayout() -> CLAY() -> Clay_EndLayout()

Notes

CLAY opens a generic empty container, that is configurable and supports nested children.

Examples

// Define an element with 16px of x and y padding
CLAY(CLAY_ID("Outer"), CLAY_LAYOUT({ .padding = {16, 16} })) {
    // A nested child element
    CLAY(CLAY_ID("SideBar"), CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM, .childGap = 16 })) {
        // Children laid out top to bottom with a 16 px gap between them
    }
    // A vertical scrolling container with a colored background
    CLAY(
        CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM, .childGap = 16 })
        CLAY_RECTANGLE({ .color = { 200, 200, 100, 255 }, .cornerRadius = CLAY_CORNER_RADIUS(10) })
        CLAY_SCROLL({ .vertical = true })
    ) {
        // child elements
    }
}

CLAY_ID

Usage

CLAY(CLAY_ID(char* idString)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_ID() -> ) -> Clay_EndLayout()

Notes

CLAY_ID() is used to generate and attach a Clay_ElementId to a layout element during declaration.

To regenerate the same ID outside of layout declaration when using utility functions such as Clay_PointerOver, use the Clay_GetElementId function.

Examples

// Tag a button with the Id "Button"
CLAY(
    CLAY_ID("Button"),
    CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_GROW() }, .padding = {16, 16}, .childGap = 16) })
) {
    // ...children
}

// Later on outside of layout code
bool buttonIsHovered = Clay_IsPointerOver(Clay_GetElementId("Button"));
if (buttonIsHovered && leftMouseButtonPressed) {
    // ... do some click handling
}

CLAY_IDI()

Clay_ElementId CLAY_IDI(char *label, int index)

An offset version of CLAY_ID. Generates a Clay_ElementId string id from the provided char *label, combined with the int index. Used for generating ids for sequential elements (such as in a for loop) without having to construct dynamic strings at runtime.

CLAY_LAYOUT

Usage

CLAY(CLAY_LAYOUT(...layout config)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_LAYOUT() -> ) -> Clay_EndLayout()

Notes

CLAY_LAYOUT() is used for configuring layout options (i.e. options that affect the final position and size of an element, its parents, siblings, and children)

Struct API (Pseudocode)

// CLAY_LAYOUT({ .member = value }) supports these options
Clay_LayoutConfig {
    Clay_LayoutDirection layoutDirection = CLAY_LEFT_TO_RIGHT (default) | CLAY_TOP_TO_BOTTOM;
    Clay_Padding padding {
        float x; float y; 
    };
    uint16_t childGap;
    Clay_ChildAlignment childAlignment {
        .x = CLAY_ALIGN_X_LEFT (default) | CLAY_ALIGN_X_CENTER | CLAY_ALIGN_X_RIGHT;
        .y = CLAY_ALIGN_Y_TOP (default) | CLAY_ALIGN_Y_CENTER | CLAY_ALIGN_Y_BOTTOM;
    };
    Clay_Sizing sizing { // Recommended to use the provided macros here - see #sizing for more in depth explanation
        .width = CLAY_SIZING_FIT(float min, float max) (default) | CLAY_SIZING_GROW(float min, float max) | CLAY_SIZING_FIXED(width) | CLAY_SIZING_PERCENT(float percent)
        .height = CLAY_SIZING_FIT(float min, float max) (default) | CLAY_SIZING_GROW(float min, float max) | CLAY_SIZING_FIXED(height) | CLAY_SIZING_PERCENT(float percent)
    }; // See CLAY_SIZING_GROW() etc for more details
};

As with all config macros, CLAY_LAYOUT() accepts designated initializer syntax and provides default values for any unspecified struct members.

Fields

.layoutDirection - Clay_LayoutDirection

CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM })

Controls the axis / direction in which child elements are laid out. Available options are CLAY_LEFT_TO_RIGHT (default) and CLAY_TOP_TO_BOTTOM.

Did you know that "left to right" and "top to bottom" both have 13 letters?

---

.padding - Clay_Padding

CLAY_LAYOUT({ .padding = { .x = 16, .y = 16 } })

Controls horizontal and vertical white-space "padding" around the outside of child elements.

---

.childGap - uint16_t

CLAY_LAYOUT({ .childGap = 16 })

Controls the white-space between child elements as they are laid out. When .layoutDirection is CLAY_LEFT_TO_RIGHT (default), this will be horizontal space, whereas for CLAY_TOP_TO_BOTTOM it will be vertical space.

---

.childAlignment - Clay_ChildAlignment

CLAY_LAYOUT({ .childAlignment = { .x = CLAY_ALIGN_X_LEFT, .y = CLAY_ALIGN_Y_CENTER } })

Controls the alignment of children relative to the height and width of the parent container. Available options are:

.x = CLAY_ALIGN_X_LEFT (default) | CLAY_ALIGN_X_CENTER | CLAY_ALIGN_X_RIGHT;
.y = CLAY_ALIGN_Y_TOP (default) | CLAY_ALIGN_Y_CENTER | CLAY_ALIGN_Y_BOTTOM;

---

.sizing - Clay_Sizing

CLAY_LAYOUT({ .sizing = { .width = CLAY_SIZING_FIXED(300), .height = CLAY_SIZING_PERCENT(0.5) } })

Controls how final width and height of element are calculated. The same configurations are available for both the .width and .height axis. There are several options:

• CLAY_SIZING_FIT(float min, float max) (default) - The element will be sized to fit its children (plus padding and gaps), up to max. If max is left unspecified, it will default to FLOAT_MAX. When elements are compressed to fit into a smaller parent, this element will not shrink below min.

• CLAY_SIZING_GROW(float min, float max) - The element will grow to fill available space in its parent, up to max. If max is left unspecified, it will default to FLOAT_MAX. When elements are compressed to fit into a smaller parent, this element will not shrink below min.

• CLAY_SIZING_FIXED(float fixed) - The final size will always be exactly the provided fixed value. Shorthand for CLAY_SIZING_FIT(fixed, fixed)

• CLAY_SIZING_PERCENT(float percent) - Final size will be a percentage of parent size, minus padding and child gaps. percent is assumed to be a float between 0 and 1.

Example Usage

CLAY(CLAY_ID("Button"), CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_GROW() }, .padding = {16, 16}, .childGap = 16) }) {
    // Children will be laid out vertically with 16px of padding around and between
}

CLAY_RECTANGLE

Usage

CLAY(CLAY_RECTANGLE(...rectangle config)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_RECTANGLE() -> ) -> Clay_EndLayout()

Notes

RECTANGLE configures a clay element to background-fill its bounding box with a color. It uses Clay_RectangleElementConfig for rectangle specific options.

Struct API (Pseudocode)

// CLAY_RECTANGLE({ .member = value }) supports these options
Clay_RectangleElementConfig {
    Clay_Color color {
        float r; float g; float b; float a;
    };
    float cornerRadius;

    #ifdef CLAY_EXTEND_CONFIG_RECTANGLE
        // Contents of CLAY_EXTEND_CONFIG_RECTANGLE will be pasted here
    #endif
}

As with all config macros, CLAY_RECTANGLE() accepts designated initializer syntax and provides default values for any unspecified struct members.

Extension

The underlying Clay_RectangleElementConfig can be extended with new members by using:

#define CLAY_EXTEND_CONFIG_RECTANGLE float newField;
#include "clay.h" // Define your extension before including clay.h

Fields

.color - Clay_Color

CLAY_RECTANGLE({ .color = {120, 120, 120, 255} })

Conventionally accepts rgba float values between 0 and 255, but interpretation is left up to the renderer and does not affect layout.

---

.cornerRadius - float

CLAY_RECTANGLE({ .cornerRadius = { .topLeft = 16, .topRight = 16, .bottomLeft = 16, .bottomRight = 16 })

Defines the radius in pixels for the arc of rectangle corners (0 is square, rectangle.width / 2 is circular).

Note that the CLAY_CORNER_RADIUS(radius) function-like macro is available to provide short hand for setting all four corner radii to the same value. e.g. CLAY_BORDER({ .cornerRadius = CLAY_CORNER_RADIUS(10) })

Rendering

Element is subject to culling. Otherwise, a single Clay_RenderCommands with commandType = CLAY_RENDER_COMMAND_TYPE_RECTANGLE will be created, with renderCommand->elementConfig.rectangleElementConfig containing a pointer to the element's Clay_RectangleElementConfig.

Examples

// Declare a reusable rectangle config, with a purple color and 10px rounded corners
Clay_RectangleElementConfig rectangleConfig = (Clay_RectangleElementConfig) { .color = { 200, 200, 100, 255 }, .cornerRadius = CLAY_CORNER_RADIUS(10) };
// Declare a rectangle element using a reusable config
CLAY(CLAY_RECTANGLE(rectangleConfig)) {}
// Declare a retangle element using an inline config
CLAY(CLAY_RECTANGLE({ .color = { 200, 200, 100, 255 }, .cornerRadius = CLAY_CORNER_RADIUS(10) })) {
    // child elements
}
// Declare a scrolling container with a colored background
CLAY(
    CLAY_RECTANGLE({ .color = { 200, 200, 100, 255 }, .cornerRadius = CLAY_CORNER_RADIUS(10) })
    CLAY_SCROLL({ .vertical = true })
) {
    // child elements
}

CLAY_TEXT

Usage

CLAY_TEXT(Clay_String textContents, Clay_TextElementConfig *textConfig);

Lifecycle

Clay_BeginLayout() -> CLAY_TEXT() -> Clay_EndLayout()

Notes

TEXT is a measured, auto-wrapped text element. It uses Clay_TextElementConfig to configure text specific options.

Note that Clay_TextElementConfig uses uint32_t fontId. Font ID to font asset mapping is managed in user code and passed to render commands.

Struct API (Pseudocode)

// CLAY_TEXT(text, CLAY_TEXT_CONFIG({ .member = value })) supports these options
Clay_TextElementConfig {
    Clay_Color textColor {
        float r; float g; float b; float a;
    };
    uint16_t fontId;
    uint16_t fontSize;
    uint16_t letterSpacing;
    uint16_t lineHeight;
    Clay_TextElementConfigWrapMode wrapMode {
        CLAY_TEXT_WRAP_WORDS (default),
	CLAY_TEXT_WRAP_NEWLINES,
	CLAY_TEXT_WRAP_NONE,
    };

    #ifdef CLAY_EXTEND_CONFIG_TEXT
        // Contents of CLAY_EXTEND_CONFIG_TEXT will be pasted here
    #endif
};

As with all config macros, CLAY_TEXT_CONFIG() accepts designated initializer syntax and provides default values for any unspecified struct members.

Extension

The underlying Clay_TextElementConfig can be extended with new members by using:

#define CLAY_EXTEND_CONFIG_TEXT float newField;
#include "clay.h" // Define your extension before including clay.h

Fields

.textColor

CLAY_TEXT_CONFIG(.textColor = {120, 120, 120, 255})

Conventionally accepts rgba float values between 0 and 255, but interpretation is left up to the renderer and does not affect layout.

---

.fontId

CLAY_TEXT_CONFIG(.fontId = FONT_ID_LATO)

It's up to the user to load fonts and create a mapping from fontId to a font that can be measured and rendered.

---

.fontSize

CLAY_TEXT_CONFIG(.fontSize = 16)

Font size is generally thought of as x pixels tall, but interpretation is left up to the user & renderer.

---

.letterSpacing

CLAY_TEXT_CONFIG(.letterSpacing = 1)

.letterSpacing results in horizontal white space between individual rendered characters.

---

.lineHeight

CLAY_TEXT_CONFIG(.lineHeight = 20)

.lineHeight - when non zero - forcibly sets the height of each wrapped line of text to .lineheight pixels tall. Will affect the layout of both parents and siblings. A value of 0 will use the measured height of the font.

---

.wrapMode

CLAY_TEXT_CONFIG(.wrapMode = CLAY_TEXT_WRAP_NONE)

.wrapMode specifies under what conditions text should wrap.

Available options are:

• CLAY_TEXT_WRAP_WORDS (default) - Text will wrap on whitespace characters as container width shrinks, preserving whole words.
• CLAY_TEXT_WRAP_NEWLINES - will only wrap when encountering newline characters.
• CLAY_TEXT_WRAP_NONE - Text will never wrap even if its container is compressed beyond the text measured width.

---

Examples

// Define a font somewhere in your code
const uint32_t FONT_ID_LATO = 3;
// ..
CLAY_TEXT(CLAY_STRING("John Smith"), CLAY_TEXT_CONFIG({ .fontId = FONT_ID_LATO, .fontSize = 24, .textColor = {255, 0, 0, 255} }));
// Rendering example
Font fontToUse = LoadedFonts[renderCommand->elementConfig.textElementConfig->fontId];

Rendering

Element is subject to culling. Otherwise, multiple Clay_RenderCommands with commandType = CLAY_RENDER_COMMAND_TYPE_TEXT may be created, one for each wrapped line of text.

Clay_RenderCommand.textContent will be populated with a Clay_String slice of the original string passed in (i.e. wrapping doesn't reallocate, it just returns a Clay_String pointing to the start of the new line with a length)

CLAY_IMAGE

Usage

CLAY(CLAY_IMAGE(...image config)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_IMAGE() -> ) -> Clay_EndLayout()

Notes

IMAGE configures a clay element to render an image as its background. It uses Clay_ImageElementConfig for image specific options.

Struct API (Pseudocode)

Clay_ImageElementConfig {
    Clay_Dimensions sourceDimensions {
        float width; float height; 
    };
    // --
    #ifndef CLAY_EXTEND_CONFIG_IMAGE
        void * imageData; // Note: This field will be replaced if #define CLAY_EXTEND_CONFIG_IMAGE is specified
    #else CLAY_EXTEND_CONFIG_IMAGE
        // Contents of CLAY_EXTEND_CONFIG_IMAGE will be pasted here
    #endif
};

As with all config macros, CLAY_IMAGE_CONFIG() accepts designated initializer syntax and provides default values for any unspecified struct members.

Extension

The underlying Clay_ImageElementConfig can be extended with new members by using:

#define CLAY_EXTEND_CONFIG_IMAGE float newField;
#include "clay.h" // Define your extension before including clay.h

Fields

.sourceDimensions - Clay_Dimensions

CLAY_IMAGE_CONFIG(.sourceDimensions = { 1024, 768 })

Used to perform aspect ratio scaling on the image element. As of this version of clay, aspect ratio scaling only applies to the height of an image (i.e. image height will scale with width growth and limitations, but width will not scale with height growth and limitations)

---

.imageData - void *

CLAY_IMAGE_CONFIG(.imageData = &myImage)

.imageData is a generic void pointer that can be used to pass through image data to the renderer. Note: this field is generally not recommended for usage due to the lack of type safety, see #define CLAY_EXTEND_CONFIG_IMAGE in Preprocessor Directives for an alternative.

// Load an image somewhere in your code
Image profilePicture = LoadImage("profilePicture.png");
// Note that when rendering, .imageData will be void* type.
CLAY(CLAY_IMAGE({ .imageData = &profilePicture, .sourceDimensions = { 60, 60 } })) {}

// OR ----------------

// Extend CLAY_CUSTOM_IMAGE_CONFIG with your custom image format
#define CLAY_EXTEND_CONFIG_IMAGE struct t_Image image;
// Extensions need to happen _before_ the clay include
#include "clay.h"

typedef struct t_Image {
    ImageFormat format;
    u8int_t *internalData;
    // ... etc
} Image;

// You can now use CLAY_IMAGE with your custom type and still have type safety & code completion
CLAY(CLAY_IMAGE({ .image = { .format = IMAGE_FORMAT_RGBA, .internalData = &imageData }, .sourceDimensions = { 60, 60 } })) {}

Examples

// Load an image somewhere in your code
Image profilePicture = LoadImage("profilePicture.png");
// Declare a reusable image config
Clay_ImageElementConfig imageConfig = (Clay_ImageElementConfig) { .imageData = &profilePicture, .height = 60, .width = 60 };
// Declare an image element using a reusable config
CLAY(CLAY_IMAGE(imageConfig)) {}
// Declare an image element using an inline config
CLAY(CLAY_IMAGE({ .imageData = &profilePicture, .height = 60, .width = 60 })) {}
// Rendering example
Image *imageToRender = renderCommand->elementConfig.imageElementConfig->imageData;

Rendering

Element is subject to culling. Otherwise, a single Clay_RenderCommands with commandType = CLAY_RENDER_COMMAND_TYPE_IMAGE will be created. The user will need to access renderCommand->elementConfig.imageElementConfig->imageData to retrieve image data referenced during layout creation. It's also up to the user to decide how / if they wish to blend rectangleElementConfig->color with the image.

CLAY_SCROLL

Usage

CLAY(CLAY_SCROLL(...scroll config)) {}

Lifecycle

Clay_SetPointerState() -> Clay_UpdateScrollContainers() -> Clay_BeginLayout() -> CLAY( -> CLAY_SCROLL() -> ) -> Clay_EndLayout()

Notes

SCROLL configures the element as a scrolling container, enabling masking of children that extend beyond its boundaries. It uses Clay_ScrollElementConfig to configure scroll specific options.

Note: In order to process scrolling based on pointer position and mouse wheel or touch interactions, you must call Clay_SetPointerState() and Clay_UpdateScrollContainers() before calling BeginLayout.

Struct Definition (Pseudocode)

Clay_ScrollElementConfig {
    bool horizontal;
    bool vertical;
};

As with all config macros, CLAY_SCROLL() accepts designated initializer syntax and provides default values for any unspecified struct members.

Fields

.horizontal - bool

CLAY_SCROLL(.horizontal = true)

Enables or disables horizontal scrolling for this container element.

---

.vertical - bool

CLAY_SCROLL(.vertical = true)

Enables or disables vertical scrolling for this container element.

---

Rendering

Enabling scroll for an element will result in two additional render commands:

• commandType = CLAY_RENDER_COMMAND_TYPE_SCISSOR_START, which should create a rectangle mask with its boundingBox and is not subject to culling
• commandType = CLAY_RENDER_COMMAND_TYPE_SCISSOR_END, which disables the previous rectangle mask and is not subject to culling

Examples

CLAY(CLAY_SCROLL(.vertical = true)) {
    // Create child content with a fixed height of 5000
    CLAY(CLAY_ID("ScrollInner"), CLAY_LAYOUT({ .sizing = { .height = CLAY_SIZING_FIXED(5000) } })) {}
}

CLAY_BORDER

Usage

CLAY(CLAY_BORDER(...border config)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_BORDER() -> ) -> Clay_EndLayout()

Notes

BORDER adds borders to the edges or between the children of elements. It uses Clay_BorderElementConfig to configure border specific options.

Struct Definition (Pseudocode)

typedef struct Clay_BorderElementConfig
{
    Clay_Border left {
        float width;
        Clay_Color color {
            float r; float g; float b; float a;
        };
    };
    Clay_Border right // Exactly the same as left
    Clay_Border top // Exactly the same as left
    Clay_Border bottom // Exactly the same as left
    Clay_Border betweenChildren // Exactly the same as left
    Clay_CornerRadius cornerRadius {
        float topLeft;
        float topRight;
        float bottomLeft;
        float bottomRight;
    };
} Clay_BorderElementConfig;

Usage

As with all config macros, CLAY_BORDER() accepts designated initializer syntax and provides default values for any unspecified struct members.

Fields

.left, .right, .top, .bottom - Clay_Border

CLAY_BORDER({ .left = { 2, COLOR_RED }, .right = { 4, COLOR_YELLOW } /* etc */ })

Indicates to the renderer that a border of .color should be draw at the specified edges of the bounding box, overlapping the box contents by .width.

This means that border configuration does not affect layout, as the width of the border doesn't contribute to the total container width or layout position. Border containers with zero padding will be drawn over the top of child elements.

---

.betweenChildren - Clay_Border

CLAY_BORDER({ .betweenChildren = { 2, COLOR_RED } })

Configures the width and color of borders to be drawn between children. These borders will be vertical lines if the parent uses .layoutDirection = CLAY_LEFT_TO_RIGHT and horizontal lines if the parent uses CLAY_TOP_TO_BOTTOM. Unlike .left, .top etc, this option will generate additional rectangle render commands representing the borders between children. As a result, the renderer does not need to specifically implement rendering for these border elements.

---

.cornerRadius - float

CLAY_BORDER({ .cornerRadius = 16 })

Defines the radius in pixels for the arc of border corners (0 is square, rectangle.width / 2 is circular). It is up to the renderer to decide how to interpolate between differing border widths and colors across shared corners.

Note that the CLAY_CORNER_RADIUS(radius) function-like macro is available to provide short hand for setting all four corner radii to the same value. e.g. CLAY_BORDER(.cornerRadius = CLAY_CORNER_RADIUS(10))

Convenience Macros

There are some common cases for border configuration that are repetitive, i.e. specifying the same border around all four edges. Some convenience macros are provided for these cases:

• CLAY_BORDER_CONFIG_OUTSIDE({ .width = 2, .color = COLOR_RED }) - Shorthand for configuring all 4 outside borders at once.`
• CLAY_BORDER_CONFIG_OUTSIDE_RADIUS(width, color, radius) - Shorthand for configuring all 4 outside borders at once, with the provided .cornerRadius. Note this is a function-like macro and does not take .member = value syntax.
• CLAY_BORDER_CONFIG_ALL({ .width = 2, .color = COLOR_RED }) - Shorthand for configuring all 4 outside borders and .betweenChildren at once.
• CLAY_BORDER_CONFIG_ALL_RADIUS(width, color, radius) - Shorthand for configuring all 4 outside borders and .betweenChildren at once, with the provided cornerRadius. Note this is a function-like macro and does not take .member = value syntax.

Examples

// 300x300 container with a 1px red border around all the edges
CLAY(
    CLAY_ID("OuterBorder"),
    CLAY_LAYOUT({ .sizing = { .width = CLAY_SIZING_FIXED(300), .height = CLAY_SIZING_FIXED(300)}),
    CLAY_BORDER_CONFIG_OUTSIDE({ .color = COLOR_RED, .width = 1 })
) {
    // ...
}

// Container with a 3px yellow bottom border
CLAY(
    CLAY_ID("OuterBorder"),
    CLAY_BORDER({ .bottom = { .color = COLOR_YELLOW, .width = 3 } })
) {
    // ...
}

// Container with a 5px curved border around the edges, and a 5px blue border between all children laid out top to bottom
CLAY(
    CLAY_ID("OuterBorder"),
    CLAY_LAYOUT({ .layoutDirection = CLAY_TOP_TO_BOTTOM }),
    CLAY_BORDER_CONFIG_ALL_RADIUS(5, COLOR_BLUE, 5)
) {
    // Child
    // -- 5px blue border will be here --
    // Child
    // -- 5px blue border will be here --
    // Child
}

Rendering

Element is subject to culling. Otherwise, a single Clay_RenderCommand with commandType = CLAY_RENDER_COMMAND_TYPE_BORDER representing the container will be created. Rendering of borders and rounded corners is left up to the user. See the provided Raylib Renderer for examples of how to draw borders using line and curve primitives.

CLAY_FLOATING

Usage

CLAY(CLAY_FLOATING(...floating config)) {}

Lifecycle

Clay_BeginLayout() -> CLAY( -> CLAY_FLOATING() -> ) -> Clay_EndLayout()

Notes

FLOATING defines an element that "floats" above other content. Typical use-cases include tooltips and modals.

Floating containers:

• With the default configuration, attach to the top left corner of their "parent"
• Don't affect the width and height of their parent
• Don't affect the positioning of sibling elements
• Depending on their z-index can appear above or below other elements, partially or completely occluding them
• Apart from positioning, function just like standard CLAY elements - including expanding to fit their children, etc.

The easiest mental model to use when thinking about floating containers is that they are a completely separate UI hierarchy, attached to a specific x,y point on their "parent".

Floating elements uses Clay_FloatingElementConfig to configure specific options.

Struct Definition (Pseudocode)

Clay_FloatingElementConfig {
    Clay_Vector2 offset {
        float x, float y
    };
    Clay_Dimensions expand {
        float width, float height
    };
    uint16_t zIndex;
    uint32_t parentId;
    Clay_FloatingAttachPoints attachment {
        .element = CLAY_ATTACH_POINT_LEFT_TOP (default) | CLAY_ATTACH_POINT_LEFT_CENTER | CLAY_ATTACH_POINT_LEFT_BOTTOM | CLAY_ATTACH_POINT_CENTER_TOP | CLAY_ATTACH_POINT_CENTER_CENTER | CLAY_ATTACH_POINT_CENTER_BOTTOM | CLAY_ATTACH_POINT_RIGHT_TOP | CLAY_ATTACH_POINT_RIGHT_CENTER | CLAY_ATTACH_POINT_RIGHT_BOTTOM
        .parent = CLAY_ATTACH_POINT_LEFT_TOP (default) | CLAY_ATTACH_POINT_LEFT_CENTER | CLAY_ATTACH_POINT_LEFT_BOTTOM | CLAY_ATTACH_POINT_CENTER_TOP | CLAY_ATTACH_POINT_CENTER_CENTER | CLAY_ATTACH_POINT_CENTER_BOTTOM | CLAY_ATTACH_POINT_RIGHT_TOP | CLAY_ATTACH_POINT_RIGHT_CENTER | CLAY_ATTACH_POINT_RIGHT_BOTTOM
    };
    Clay_PointerCaptureMode captureMode {
        CLAY_POINTER_CAPTURE_MODE_CAPTURE (default),
        CLAY_POINTER_CAPTURE_MODE_PASSTHROUGH
    };
};

As with all config macros, CLAY_FLOATING() accepts designated initializer syntax and provides default values for any unspecified struct members.

Fields

.offset - Clay_Vector2

CLAY_FLOATING({ .offset = { -24, -24 } })

Used to apply a position offset to the floating container after all other layout has been calculated.

---

.expand - Clay_Dimensions

CLAY_FLOATING({ .expand = { 16, 16 } })

Used to expand the width and height of the floating container before laying out child elements.

---

.zIndex - float

CLAY_FLOATING({ .zIndex = 1 })

All floating elements (as well as their entire child hierarchies) will be sorted by .zIndex order before being converted to render commands. If render commands are drawn in order, elements with higher .zIndex values will be drawn on top.

---

.parentId - uint32_t

CLAY_FLOATING({ .parentId = Clay_GetElementId("HeaderButton").id })

By default, floating containers will "attach" to the parent element that they are declared inside. However, there are cases where this limitation could cause significant performance or ergonomics problems. .parentId allows you to specify a CLAY_ID().id to attach the floating container to. The parent element with the matching id can be declared anywhere in the hierarchy, it doesn't need to be declared before or after the floating container in particular.

Consider the following case:

// Load an image somewhere in your code
CLAY(CLAY_IDI("SidebarButton", 1), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 1) {
        CLAY_FLOATING(/* floating config... */)
    }
}
CLAY(CLAY_IDI("SidebarButton", 2), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 2) {
        CLAY_FLOATING(/* floating config... */)
    }
}
CLAY(CLAY_IDI("SidebarButton", 3), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 3) {
        CLAY_FLOATING(/* floating config... */)
    }
}
CLAY(CLAY_IDI("SidebarButton", 4), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 4) {
        CLAY_FLOATING(/* floating config... */)
    }
}
CLAY(CLAY_IDI("SidebarButton", 5), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 5) {
        CLAY_FLOATING(/* floating config... */)
    }
}

The definition of the above UI is significantly polluted by the need to conditionally render floating tooltips as a child of many possible elements. The alternative, using parentId, looks like this:

// Load an image somewhere in your code
CLAY(CLAY_IDI("SidebarButton", 1), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
}
CLAY(CLAY_IDI("SidebarButton", 2), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
}
CLAY(CLAY_IDI("SidebarButton", 3), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
}
CLAY(CLAY_IDI("SidebarButton", 4), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
}
CLAY(CLAY_IDI("SidebarButton", 5), &CLAY_LAYOUT_DEFAULT) {
    // .. some button contents
}

// Any other point in the hierarchy
CLAY_FLOATING(CLAY_ID("OptionTooltip"), &CLAY_LAYOUT_DEFAULT, CLAY_FLOATING(.parentId = CLAY_IDI("SidebarButton", tooltip.attachedButtonIndex).id)) {
    // Tooltip contents...
}

---

.attachment - Clay_FloatingAttachPoints

CLAY_FLOATING(.attachment = { .element = CLAY_ATTACH_POINT_LEFT_CENTER, .parent = CLAY_ATTACH_POINT_RIGHT_TOP });

In terms of positioning the floating container, .attachment specifies

• The point on the floating container (.element)
• The point on the parent element that it "attaches" to (.parent)

You can mentally visualise this as finding a point on the floating container, then finding a point on the parent, and lining them up over the top of one another.

For example:

"Attach the LEFT_CENTER of the floating container to the RIGHT_TOP of the parent"

CLAY_FLOATING({ .attachment = { .element = CLAY_ATTACH_POINT_LEFT_CENTER, .parent = CLAY_ATTACH_POINT_RIGHT_TOP } });

.pointerCaptureMode - Clay_PointerCaptureMode

CLAY_FLOATING({ .pointerCaptureMode = CLAY_POINTER_CAPTURE_MODE_CAPTURE })

Controls whether pointer events like hover and click should pass through to content underneath this floating element, or whether the pointer should be "captured" by this floating element. Defaults to CLAY_POINTER_CAPTURE_MODE_CAPTURE.

Examples

// Horizontal container with three option buttons
CLAY(CLAY_ID("OptionsList"), CLAY_LAYOUT(.childGap = 16)) {
    CLAY_RECTANGLE(CLAY_IDI("Option", 1), CLAY_LAYOUT(.padding = {16, 16}), CLAY_RECTANGLE(.color = COLOR_BLUE)) {
        CLAY_TEXT(CLAY_IDI("OptionText", 1), CLAY_STRING("Option 1"), CLAY_TEXT_CONFIG());
    }
    CLAY_RECTANGLE(CLAY_IDI("Option", 2), CLAY_LAYOUT(.padding = {16, 16}), CLAY_RECTANGLE(.color = COLOR_BLUE)) {
        CLAY_TEXT(CLAY_IDI("OptionText", 2), CLAY_STRING("Option 2"), CLAY_TEXT_CONFIG());
        // Floating tooltip will attach above the "Option 2" container and not affect widths or positions of other elements
        CLAY_FLOATING(CLAY_ID("OptionTooltip"), &CLAY_LAYOUT_DEFAULT, CLAY_FLOATING({ .zIndex = 1, .attachment = { .element = CLAY_ATTACH_POINT_CENTER_BOTTOM, .parent = CLAY_ATTACH_POINT_CENTER_TOP } })) {
            CLAY_TEXT(CLAY_IDI("OptionTooltipText", 1), CLAY_STRING("Most popular!"), CLAY_TEXT_CONFIG());
        }
    }
    CLAY_RECTANGLE(CLAY_IDI("Option", 3), CLAY_LAYOUT(.padding = {16, 16}), CLAY_RECTANGLE(.color = COLOR_BLUE)) {
        CLAY_TEXT(CLAY_IDI("OptionText", 3), CLAY_STRING("Option 3"), CLAY_TEXT_CONFIG());
    }
}

// Floating containers can also be declared elsewhere in a layout, to avoid branching or polluting other UI
for (int i = 0; i < 1000; i++) {
    CLAY(CLAY_IDI("Option", i + 1), &CLAY_LAYOUT_DEFAULT) {
        // ...
    }
}
// Note the use of "parentId".
// Floating tooltip will attach above the "Option 2" container and not affect widths or positions of other elements
CLAY_FLOATING(CLAY_ID("OptionTooltip"), &CLAY_LAYOUT_DEFAULT, CLAY_FLOATING({ .parentId = CLAY_IDI("Option", 2).id, .zIndex = 1, .attachment = { .element = CLAY_ATTACH_POINT_CENTER_BOTTOM, .parent = CLAY_ATTACH_POINT_TOP_CENTER } })) {
    CLAY_TEXT(CLAY_IDI("OptionTooltipText", 1), CLAY_STRING("Most popular!"), CLAY_TEXT_CONFIG());
}

When using .parentId, the floating container can be declared anywhere after BeginLayout and before EndLayout. The target element matching the .parentId doesn't need to exist when CLAY_FLOATING is called.

Rendering

CLAY_FLOATING elements will not generate any render commands.

CLAY_CUSTOM_ELEMENT

Usage

CLAY_CUSTOM_ELEMENT(Clay_ElementId id, Clay_LayoutConfig *layoutConfig, Clay_CustomElementConfig *customConfig);

Lifecycle

Clay_BeginLayout() -> CLAY_CUSTOM_ELEMENT() -> Clay_EndLayout()

Notes

CUSTOM_ELEMENT allows the user to pass custom data to the renderer.

Struct Definition (Pseudocode)

typedef struct
{
    #ifndef CLAY_EXTEND_CONFIG_CUSTOM
        void * customData; // Note: This field will be replaced if #define CLAY_EXTEND_CONFIG_CUSTOM is specified
    #else CLAY_EXTEND_CONFIG_CUSTOM
        // Contents of CLAY_EXTEND_CONFIG_CUSTOM will be pasted here
    #endif
} Clay_CustomElementConfig;

As with all config macros, CLAY_CUSTOM_ELEMENT_CONFIG() accepts designated initializer syntax and provides default values for any unspecified struct members.

Extension

The underlying Clay_ImageCustomConfig can be extended with new members by using:

#define CLAY_EXTEND_CONFIG_CUSTOM float newField;
#include "clay.h" // Define your extension before including clay.h

Fields

.customData - void *

CLAY_CUSTOM_CONFIG(.customData = &myCustomData)

.customData is a generic void pointer that can be used to pass through custom data to the renderer. Note: this field is generally not recommended for usage due to the lack of type safety, see #define CLAY_EXTEND_CONFIG_CUSTOM in Preprocessor Directives for an alternative.

Examples

// Extend CLAY_CUSTOM_ELEMENT_CONFIG with your custom data
#define CLAY_EXTEND_CONFIG_CUSTOM struct t_CustomElementData customData;
// Extensions need to happen _before_ the clay include
#include "clay.h"

enum CustomElementType {
    CUSTOM_ELEMENT_TYPE_MODEL,
    CUSTOM_ELEMENT_TYPE_VIDEO
};

// A rough example of how you could handle laying out 3d models in your UI
typedef struct t_CustomElementData {
    CustomElementType type;
    union {
        Model model;
        Video video;
        // ...
    };
} CustomElementData;

Model myModel = Load3DModel(filePath);
CustomElement modelElement = (CustomElement) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel }
// ...
CLAY(id, style) {
    // This config is type safe and contains the CustomElementData struct
    CLAY_CUSTOM_ELEMENT(id, layout, CLAY_CUSTOM_ELEMENT_CONFIG(.customData = { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel })) {}
}

// Later during your rendering
switch (renderCommand->commandType) {
    // ...
    case CLAY_RENDER_COMMAND_TYPE_CUSTOM: {
        // Your extended struct is passed through
        CustomElementData *data = renderCommand->elementConfig.customElementConfig->customData;
        if (!customElement) continue;
        switch (customElement->type) {
            case CUSTOM_ELEMENT_TYPE_MODEL: {
                // Render your 3d model here
                break;
            }
            case CUSTOM_ELEMENT_TYPE_VIDEO: {
                // Render your video here
                break;
            }
            // ...
        }
        break;
    }
}

Rendering

Element is subject to culling. Otherwise, a single Clay_RenderCommand with commandType = CLAY_RENDER_COMMAND_TYPE_CUSTOM will be created.

Data Structures & Definitions

Clay_ElementId

typedef struct {
    uint32_t id;
    uint32_t offset;
    uint32_t baseId;
    Clay_String stringId;
} Clay_ElementId;

Returned by CLAY_ID and CLAY_IDI, this struct contains a hash id, as well as the source string that was used to generate it.

Fields

.id - uint32_t

A unique ID derived from the string passed to CLAY_ID or CLAY_IDI.

---

.offset - uint32_t

If this id was generated using CLAY_IDI, .offset is the value passed as the second argument. For CLAY_ID, this will always be 0.

---

.baseId - uint32_t

If this id was generated using CLAY_IDI, .baseId is the hash of the base string passed, before it is additionally hashed with .offset. For CLAY_ID, this will always be the same as .id.

---

.stringId - Clay_String

Stores the original string that was passed in when CLAY_ID or CLAY_IDI were called.

Clay_RenderCommandArray

typedef struct
{
	uint32_t capacity;
	uint32_t length;
	Clay_RenderCommand *internalArray;
} Clay_RenderCommandArray;

Returned by Clay_EndLayout, this array contains the Clay_RenderCommands representing the calculated layout.

Fields

.capacity - uint32_t

Represents the total capacity of the allocated memory in .internalArray.

---

.length - uint32_t

Represents the total number of Clay_RenderCommand elements stored consecutively at the address .internalArray.

---

.internalArray - Clay_RenderCommand

An array of Clay_RenderCommands representing the calculated layout. If there was at least one render command, this array will contain elements from .internalArray[0] to .internalArray[.length - 1].

Clay_RenderCommand

typedef struct
{
    Clay_BoundingBox boundingBox;
    Clay_ElementConfigUnion config;
    Clay_String text;
    uint32_t id;
    Clay_RenderCommandType commandType;
} Clay_RenderCommand;

Fields

.commandType - Clay_RenderCommandType

An enum indicating how this render command should be handled. Possible values include:

• CLAY_RENDER_COMMAND_TYPE_NONE - Should be ignored by the renderer, and never emitted by clay under normal conditions.
• CLAY_RENDER_COMMAND_TYPE_RECTANGLE - A rectangle should be drawn, configured with .config.rectangleElementConfig
• CLAY_RENDER_COMMAND_TYPE_BORDER - A border should be drawn, configured with .config.borderElementConfig
• CLAY_RENDER_COMMAND_TYPE_TEXT - Text should be drawn, configured with .config.textElementConfig
• CLAY_RENDER_COMMAND_TYPE_IMAGE - An image should be drawn, configured with .config.imageElementConfig
• CLAY_RENDER_COMMAND_TYPE_SCISSOR_START - Named after glScissor, this indicates that the renderer should begin culling any subsequent pixels that are drawn outside the .boundingBox of this render command.
• CLAY_RENDER_COMMAND_TYPE_SCISSOR_END - Only ever appears after a matching CLAY_RENDER_COMMAND_TYPE_SCISSOR_START command, and indicates that the scissor has ended.
• CLAY_RENDER_COMMAND_TYPE_CUSTOM - A custom render command controlled by the user, configured with .config.customElementConfig

---

.boundingBox - Clay_BoundingBox

typedef struct {
    float x, y, width, height;
} Clay_BoundingBox;

A rectangle representing the bounding box of this render command, with .x and .y representing the top left corner of the element.

---

.config - Clay_ElementConfigUnion

A C union containing various pointers to config data, with the type dependent on .commandType. Possible values include:

• config.rectangleElementConfig - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_RECTANGLE. See CLAY_RECTANGLE for details.
• config.textElementConfig - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_TEXT. See CLAY_TEXT for details.
• config.imageElementConfig - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_IMAGE. See CLAY_IMAGE for details.
• config.borderElementConfig - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_BORDER. See CLAY_BORDER for details.
• config.customElementConfig - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_CUSTOM. See CLAY_CUSTOM for details.
• config.floatingElementConfig - Not used and will always be NULL.
• config.scrollElementConfig - Not used and will always be NULL.

---

.text - Clay_String

Only used if .commandType == CLAY_RENDER_COMMAND_TYPE_TEXT. A Clay_String containing a string slice (char *chars, int length) representing text to be rendered. Note: This string is not guaranteed to be null terminated. Clay saves significant performance overhead by using slices when wrapping text instead of having to clone new null terminated strings. If your renderer does not support ptr, length style strings (e.g. Raylib), you will need to clone this to a new C string before rendering.

---

.id - uint32_t

The id that was originally used with the element macro that created this render command. See CLAY_ID for details.

Clay_ScrollContainerData

typedef struct
{
    Clay_Vector2 *scrollPosition;
    Clay_Dimensions scrollContainerDimensions;
    Clay_Dimensions contentDimensions;
    Clay_ScrollElementConfig config;
    bool found;
} Clay_ScrollContainerData;

Fields

.scrollPosition - Clay_Vector2 *

A pointer to the internal scroll position of this scroll container. Mutating it will result in elements inside the scroll container shifting up / down (.y) or left / right (.x).

---

.scrollContainerDimensions - Clay_Dimensions

typedef struct {
    float width, height;
} Clay_Dimensions;

Dimensions representing the outer width and height of the scroll container itself.

---

.contentDimensions - Clay_Dimensions

typedef struct {
    float width, height;
} Clay_Dimensions;

Dimensions representing the inner width and height of the content inside the scroll container. Scrolling is only possible when the contentDimensions are larger in at least one dimension than the scrollContainerDimensions.

---

.config - Clay_ScrollElementConfig

The Clay_ScrollElementConfig for the matching scroll container element.

Clay_PointerData

typedef struct
{
    Clay_Vector2 position;
    Clay_PointerDataInteractionState state;
} Clay_PointerData;

Fields

.position - Clay_Vector2

A Vector2 containing the current x,y coordinates of the mouse pointer, which were originally passed into Clay_SetPointerState().

---

.state - Clay_PointerDataInteractionState

typedef enum
{
    CLAY_POINTER_DATA_PRESSED_THIS_FRAME,
    CLAY_POINTER_DATA_PRESSED,
    CLAY_POINTER_DATA_RELEASED_THIS_FRAME,
    CLAY_POINTER_DATA_RELEASED,
} Clay_PointerDataInteractionState;

An enum value representing the current "state" of the pointer interaction. As an example, consider the case where a user is on a desktop computer, moves the mouse pointer over a button, clicks and holds the left mouse button for a short time, then releases it:

• While the mouse pointer is over ("hovering") the button, but no mouse button has been pressed: CLAY_POINTER_DATA_RELEASED
• First frame that the user presses the left mouse button: CLAY_POINTER_DATA_PRESSED_THIS_FRAME
• All subsequent frames where the user is still holding the left mouse button: CLAY_POINTER_DATA_PRESSED
• The single frame where the left mouse button goes from pressed -> released: CLAY_POINTER_DATA_RELEASED_THIS_FRAME
• All subsequent frames while the mouse pointer is still over the button: CLAY_POINTER_DATA_RELEASED

---