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 ~4k 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.

You can also watch the introduction video for an overview of the motivation behind Clay's development and a short demo of its usage.

A screenshot of a code IDE with lots of visual and textual elements

An example GUI application built with clay

Quick Start

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"

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};

void HandleClayErrors(Clay_ErrorData errorData) {
    // See the Clay_ErrorData struct for more information
    printf("%s", errorData.errorText.chars);
    switch(errorData.errorType) {
        // etc
    }
}

// Example measure text function
static inline Clay_Dimensions MeasureText(Clay_StringSlice text, Clay_TextElementConfig *config, uintptr_t userData) {
    // Clay_TextElementConfig contains members such as fontId, fontSize, letterSpacing etc
    // Note: Clay_String->chars is not guaranteed to be null terminated
    return (Clay_Dimensions) {
            .width = text.length * config->fontSize, // <- this will only work for monospace fonts, see the renderers/ directory for more advanced text measurement
            .height = config->fontSize
    };
}

// Layout config is just a struct that can be declared statically, or inline
Clay_ElementDeclaration sidebarItemConfig = (Clay_ElementDeclaration) {
    .layout = {
        .sizing = { .width = CLAY_SIZING_GROW(0), .height = CLAY_SIZING_FIXED(50) }
    },
    .backgroundColor = COLOR_ORANGE
};

// Re-useable components are just normal functions
void SidebarItemComponent() {
    CLAY(sidebarItemConfig) {
        // children go here...
    }
}

int main() {
    // 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));

    // Note: screenWidth and screenHeight will need to come from your environment, Clay doesn't handle window related tasks
    Clay_Initialize(arena, (Clay_Dimensions) { screenWidth, screenHeight }, (Clay_ErrorHandler) { HandleClayErrors });

    while(renderLoop()) { // Will be different for each renderer / environment
        // Optional: Update internal layout dimensions to support resizing
        Clay_SetLayoutDimensions((Clay_Dimensions) { screenWidth, screenHeight });
        // Optional: Update internal pointer position for handling mouseover / click / touch events - needed for scrolling & debug tools
        Clay_SetPointerState((Clay_Vector2) { mousePositionX, mousePositionY }, isMouseDown);
        // Optional: Update internal pointer position for handling mouseover / click / touch events - needed for scrolling and debug tools
        Clay_UpdateScrollContainers(true, (Clay_Vector2) { mouseWheelX, mouseWheelY }, deltaTime);

        // All clay layouts are declared between Clay_BeginLayout and Clay_EndLayout
        Clay_BeginLayout();

        // An example of laying out a UI with a fixed width sidebar and flexible width main content
        CLAY({ .id = CLAY_ID("OuterContainer"), .layout = { .sizing = {CLAY_SIZING_GROW(0), CLAY_SIZING_GROW(0)}, .padding = CLAY_PADDING_ALL(16), .childGap = 16 }, .backgroundColor = {250,250,255,255} }) {
            CLAY({
                .id = CLAY_ID("SideBar"),
                .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_FIXED(300), .height = CLAY_SIZING_GROW(0) }, .padding = CLAY_PADDING_ALL(16), .childGap = 16 },
                .backgroundColor = COLOR_LIGHT
            }) {
                CLAY({ .id = CLAY_ID("ProfilePictureOuter"), .layout = { .sizing = { .width = CLAY_SIZING_GROW(0) }, .padding = CLAY_PADDING_ALL(16), .childGap = 16, .childAlignment = { .y = CLAY_ALIGN_Y_CENTER } }, .backgroundColor = COLOR_RED }) {
                    CLAY({ .id = CLAY_ID("ProfilePicture"), .layout = { .sizing = { .width = CLAY_SIZING_FIXED(60), .height = CLAY_SIZING_FIXED(60) }}, .image = { .imageData = &profilePicture, .sourceDimensions = {60, 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({ .id = CLAY_ID("MainContent"), .layout = { .sizing = { .width = CLAY_SIZING_GROW(0), .height = CLAY_SIZING_GROW(0) } }, .backgroundColor = COLOR_LIGHT }) {}
            }
        }

        // All clay layouts are declared between Clay_BeginLayout and Clay_EndLayout
        Clay_RenderCommandArray renderCommands = Clay_EndLayout();

        // More comprehensive rendering examples can be found in the renderers/ directory
        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->renderData.rectangle.backgroundColor);
                }
                // ... 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:

Clay_SetLayoutDimensions(dimensions)
Clay_SetPointerState(pointerPosition, isPointerDown)
Clay_UpdateScrollContainers(enableDragScrolling, scrollDelta, deltaTime)
Clay_BeginLayout()
Declare your layout with the provided Element Macros
Clay_EndLayout()
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({ configuration }). 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({ .layout = { .padding = CLAY_PADDING_ALL(8) } }) {
    // Child element 1
    CLAY_TEXT(CLAY_STRING("Hello World"), CLAY_TEXT_CONFIG({ .fontSize = 16 }));
    // Child element 2 with red background
    CLAY({ .backgroundColor = COLOR_RED }) {
        // etc
    }
}

However, unlike HTML and other declarative DSLs, this macro is 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({ .layout = { .padding = CLAY_PADDING_ALL(8) }, .backgroundColor = COLOR_RED }) {
        CLAY_TEXT(buttonText, textConfig);
    }
}

// Parent element
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(0) {
            // etc
        }
    }
    // Re-usable components
    ButtonComponent(CLAY_STRING("Click me!"));
    ButtonComponent(CLAY_STRING("No, click me!"));
});

Configuring Layout and Styling UI Elements

The layout and style of clay elements is configured with the Clay_ElementDeclaration struct passed to the CLAY() macro.

CLAY({ .layout = { .padding = { 8, 8, 8, 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. e.g. (Clay_ElementDeclaration) { .layout = { .padding = { .left = 8, .right = 8 } ....

See the Clay_ElementDeclaration API for the full list of options.

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

// Define a style in the global / file scope
Clay_ElementDeclaration reuseableStyle = (Clay_ElementDeclaration) {
    .layout = { .padding = { .left = 12 } },
    .backgroundColor = { 120, 120, 120, 255 },
    .cornerRadius = { 12, 12, 12, 12 }
};

CLAY(reuseableStyle) {
    // ...
}

Element IDs

Clay elements can optionally be tagged with a unique identifier using the .id field of an element declaration, and with the CLAY_ID() convenience macro.

// Will always produce the same ID from the same input string
CLAY({ .id = CLAY_ID("OuterContainer") }) {}

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({ .id = 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, bool isPointerDown) 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({ .backgroundColor = 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({ .layout = { .padding = CLAY_PADDING_ALL(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 .clip configuration. Clipping instructs the renderer to not draw any pixels outside the clipped element's boundaries, and by specifying the .childOffset field, the clipped element's contents can be shifted around to provide "scrolling" behaviour.

You can either calculate scrolling yourself and simply provide the current offset each frame to .childOffset, or alternatively, Clay provides a built in mechanism for tracking and updating scroll container offsets, detailed below.

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
);
// ...
// Clay internally tracks the scroll containers offset, and Clay_GetScrollOffset returns the x,y offset of the currently open element
CLAY({ .clip = vertical, .childOffset = Clay_GetScrollOffset() }) {
    // Scrolling contents
}
// .childOffset can be provided directly if you would prefer to manage scrolling outside of clay
CLAY({ .clip = vertical, .childOffset = myData.scrollContainer.offset }) {
    // Scrolling contents
}

More specific details can be found in the docs for Clay_UpdateScrollContainers, Clay_SetPointerState, Clay_ClipElementConfig and Clay_GetScrollOffset.

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({ .id = CLAY_ID("Outer"), .layout = { .layoutDirection = TOP_TO_BOTTOM } }) {
    CLAY_TEXT(CLAY_ID("Button"), text, &headerTextConfig);
    CLAY({ .id = CLAY_ID("Tooltip"), .floating = { .attachTo = CLAY_ATTACH_TO_PARENT } }) {}
    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:

#include "clay.h"

typedef enum {
    CUSTOM_ELEMENT_TYPE_MODEL,
    CUSTOM_ELEMENT_TYPE_VIDEO
} CustomElementType;

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

Model myModel = Load3DModel(filePath);
CustomElement modelElement = (CustomElement) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel }

typedef struct {
    void* memory;
    uintptr_t offset;
} Arena;

// During init
Arena frameArena = (Arena) { .memory = malloc(1024) };

// ...
CLAY(0) {
    // Custom elements only take a single pointer, so we need to store the data somewhere
    CustomElementData *modelData = (CustomElementData *)(frameArena.memory + frameArena.offset);
    *modelData = (CustomElementData) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel };
    frameArena.offset += sizeof(CustomElementData);
    CLAY({ .custom = { .customData = modelData } }) {}
}

// 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_WASM - Required when targeting Web Assembly.
CLAY_DLL - Required when creating a .Dll file.

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:

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

Running more than one Clay instance

Clay allows you to run more than one instance in a program. To do this, Clay_Initialize returns a Clay_Context* reference. You can activate a specific instance using Clay_SetCurrentContext. If Clay_SetCurrentContext is not called, then Clay will default to using the context from the most recently called Clay_Initialize.

⚠ Important: Do not render instances across different threads simultaneously, as Clay does not currently support proper multi-threading.

// Define separate arenas for the instances.
Clay_Arena arena1, arena2;
// ... allocate arenas

// Initialize both instances, storing the context for each one.
Clay_Context* instance1 = Clay_Initialize(arena1, layoutDimensions, errorHandler);
Clay_Context* instance2 = Clay_Initialize(arena2, layoutDimensions, errorHandler);

// In the program's render function, activate each instance before executing clay commands and macros.
Clay_SetCurrentContext(instance1);
Clay_BeginLayout();
// ... declare layout for instance1
Clay_RenderCommandArray renderCommands1 = Clay_EndLayout();
render(renderCommands1);

// Switch to the second instance
Clay_SetCurrentContext(instance2);
Clay_BeginLayout();
// ... declare layout for instance2
Clay_RenderCommandArray renderCommands2 = Clay_EndLayout();
render(renderCommands2);

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_Initialize -> Clay_SetMeasureTextFunction

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 accommodate 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_StringSlice text, Clay_TextElementConfig *config, uintptr_t userData), uintptr_t userData)

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_ResetMeasureTextCache

void Clay_ResetMeasureTextCache(void)

Clay caches measurements from the provided MeasureTextFunction, and this will be sufficient for the majority of use-cases. However, if the measurements can depend on external factors that clay does not know about, like DPI changes, then the cached values may be incorrect. When one of these external factors changes, Clay_ResetMeasureTextCache can be called to force clay to recalculate all string measurements in the next frame.

Clay_SetMaxElementCount

void Clay_SetMaxElementCount(uint32_t maxElementCount)

Sets the internal maximum element count that will be used in subsequent Clay_Initialize() and Clay_MinMemorySize() calls, allowing clay to allocate larger UI hierarchies.

Note: You will need to reinitialize clay, after calling Clay_MinMemorySize() to calculate updated memory requirements.

Clay_SetMaxMeasureTextCacheWordCount

void Clay_SetMaxMeasureTextCacheWordCount(uint32_t maxMeasureTextCacheWordCount)

Sets the internal text measurement cache size that will be used in subsequent Clay_Initialize() and Clay_MinMemorySize() calls, allowing clay to allocate more text. The value represents how many separate words can be stored in the text measurement cache.

Note: You will need to reinitialize clay, after calling Clay_MinMemorySize() to calculate updated memory requirements.

Clay_Initialize

Clay_Context* Clay_Initialize(Clay_Arena arena, Clay_Dimensions layoutDimensions, Clay_ErrorHandler errorHandler)

Initializes the internal memory mapping, sets the internal dimensions for layout, and binds an error handler for clay to use when something goes wrong. Returns a Clay_Context* that can optionally be given to Clay_SetCurrentContext to allow running multiple instances of clay in the same program, and sets it as the current context. See Running more than one Clay instance.

Reference: Clay_Arena, Clay_ErrorHandler, Clay_SetCurrentContext

Clay_SetCurrentContext

void Clay_SetCurrentContext(Clay_Context* context)

Sets the context that subsequent clay commands will operate on. You can get this reference from Clay_Initialize or Clay_GetCurrentContext. See Running more than one Clay instance.

Clay_GetCurrentContext

Clay_Context* Clay_GetCurrentContext()

Returns the context that clay commands are currently operating on, or null if no context has been set. See Running more than one Clay instance.

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_GetScrollOffset

Clay_Vector2 Clay_GetScrollOffset()

Returns the internally stored scroll offset for the currently open element.

Generally intended for use with clip elements and the .childOffset field to create scrolling containers.

See Scrolling Elements for more details.

// Create a horizontally scrolling container
CLAY({
    .clip = { .horizontal = true, .childOffset = Clay_GetScrollOffset() }
})

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({ .layout = { .padding = CLAY_PADDING_ALL(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_GetElementData

Clay_ElementData Clay_GetElementData(Clay_ElementId id)

Returns Clay_ElementData for the element matching the provided ID. Used to retrieve information about elements such as their final calculated bounding box.

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. CLAY requires a parameter, so if you want to create an element without any configuration, use CLAY(0).

Examples

// Define an element with 16px of x and y padding
CLAY({ .id = CLAY_ID("Outer"), .layout = { .padding = CLAY_PADDING_ALL(16) } }) {
    // A nested child element
    CLAY({ .id = CLAY_ID("SideBar"), .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({
        .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM, .childGap = 16 },
        .backgroundColor = { 200, 200, 100, 255 },
        .cornerRadius = CLAY_CORNER_RADIUS(10),
        .clip = { .vertical = true, .childOffset = Clay_GetScrollOffset() }
    }) {
        // 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,
    };
    bool hashStringContents
};

Fields

.textColor

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

Uses Clay_Color. 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.

.hashStringContents

CLAY_TEXT_CONFIG(.hashStringContents = true)

By default, clay will cache the dimensions of text measured by the provided MeasureText function based on the string's pointer and length. Setting .hashStringContents = true will cause Clay to hash the entire string contents. Used to fix incorrect measurements caused by re-use of string memory, disabled by default as it will incur significant performance overhead for very large bodies of text.

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->renderData.text->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_ID

Clay_ElementId CLAY_ID(STRING_LITERAL idString)

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

Note this macro only works with String literals and won't compile if used with a char* variable. To use a heap allocated char* string as an ID, use CLAY_SID.

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({
    .id = CLAY_ID("Button"),
    .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_GROW(0) }, .padding = CLAY_PADDING_ALL(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_SID()

Clay_ElementId CLAY_SID(Clay_String idString)

A version of CLAY_ID that can be used with heap allocated char * data. The underlying char data will not be copied internally and should live until at least the next frame.

CLAY_IDI()

Clay_ElementId CLAY_IDI(STRING_LITERAL idString, int32_t 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.

Note this macro only works with String literals and won't compile if used with a char* variable. To use a heap allocated char* string as an ID, use CLAY_SIDI.

CLAY_SIDI()

Clay_ElementId CLAY_SIDI(Clay_String idString, int32_t index)

A version of CLAY_IDI that can be used with heap allocated char * data. The underlying char data will not be copied internally and should live until at least the next frame.

CLAY_ID_LOCAL()

Usage

Clay_ElementId CLAY_ID_LOCAL(STRING_LITERAL idString)

Lifecycle

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

Notes

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

Unlike CLAY_ID which needs to be globally unique, a local ID is based on the ID of it's parent and only needs to be unique among its siblings.

As a result, local id is suitable for use in reusable components and loops.

Note this macro only works with String literals and won't compile if used with a char* variable. To use a heap allocated char* string as an ID, use CLAY_SID_LOCAL.

Examples

void RenderHeaderButton(ButtonData button) {
    CLAY({
        .id = CLAY_ID_LOCAL("HeaderButton"),
        .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_GROW(0) }, .padding = CLAY_PADDING_ALL(16), .childGap = 16 }
    }) {
        // ...children
    }
}

for (int i = 0; i < headerButtons.length; i++) {
    RenderHeaderButton(headerButtons.items[i]);
}

CLAY_SID_LOCAL()

Clay_ElementId CLAY_SID_LOCAL(Clay_String idString)

A version of CLAY_ID_LOCAL that can be used with heap allocated char * data. The underlying char data will not be copied internally and should live until at least the next frame.

CLAY_IDI_LOCAL()

Clay_ElementId CLAY_IDI_LOCAL(STRING_LITERAL idString, int32_t index)

An offset version of CLAY_ID_LOCAL. 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.

Note this macro only works with String literals and won't compile if used with a char* variable. To use a heap allocated char* string as an ID, use CLAY_SIDI_LOCAL.

CLAY_SIDI_LOCAL()

Clay_ElementId CLAY_SIDI_LOCAL(Clay_String idString, int32_t index)

A version of CLAY_IDI_LOCAL that can be used with heap allocated char * data. The underlying char data will not be copied internally and should live until at least the next frame.

Data Structures & Definitions

Clay_ElementDeclaration

The Clay_ElementDeclaration struct is the only argument to the CLAY() macro and provides configuration options for layout elements.

typedef struct {
    Clay_ElementId id;
    Clay_LayoutConfig layout;
    Clay_Color backgroundColor;
    Clay_CornerRadius cornerRadius;
    Clay_ImageElementConfig image;
    Clay_FloatingElementConfig floating;
    Clay_CustomElementConfig custom;
    Clay_ClipElementConfig clip;
    Clay_BorderElementConfig border;
    void *userData;
} Clay_ElementDeclaration;

Fields

.id - Clay_ElementID

CLAY({ .id = CLAY_ID("FileButton") })

Uses Clay_ElementId. Tags the element with an ID that can be later used to query data about the element, and gives it a human readable name in the debug tools. IDs are typically generated using the CLAY_ID, CLAY_IDI, CLAY_ID_LOCAL and CLAY_IDI_LOCAL macros.

.layout - Clay_LayoutConfig

CLAY({ .layout = { .padding = { 16, 16, 12, 12 }, .layoutDirection = CLAY_TOP_TO_BOTTOM } })

Uses Clay_LayoutConfig. Controls various settings related to layout, which can be thought of as "the size and position of this element and its children".

.backgroundColor - Clay_Color

CLAY({ .backgroundColor = {120, 120, 120, 255} } })

Uses Clay_Color. 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({ .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) })

.image - Clay_ImageElementConfig

CLAY({ .image = { .imageData = &myImage, .sourceDimensions = { 640, 480 } } })

Uses Clay_ImageElementConfig. Configures the element as an image element. Causes a render command with type IMAGE to be emitted.

.floating - Clay_FloatingElementConfig

CLAY({ .floating = { .attachTo = CLAY_ATTACH_TO_PARENT } })

Uses Clay_FloatingElementConfig. Configures the element as an floating element, which allows it to stack "in front" and "on top" of other elements without affecting sibling or parent size or position.

.custom - Clay_CustomElementConfig

CLAY({ .custom = { .customData = &my3DModel } })

Uses Clay_CustomElementConfig. Configures the element as a custom element, which allows you to pass custom data through to the renderer. Causes a render command with type CUSTOM to be emitted.

.clip - Clay_ClipElementConfig

CLAY({ .clip = { .vertical = true, .childOffset = Clay_GetScrollOffset() } })

Uses Clay_ClipElementConfig. Configures the element as a clip element, which causes child elements to be clipped / masked if they overflow, and together with the functions listed in Scrolling Elements enables scrolling of child contents.

An image demonstrating the concept of clipping which prevents rendering of a child elements pixels if they fall outside the bounds of the parent element.

.border - Clay_BorderElementConfig

CLAY({ .border = { .width = { .left = 5 }, .color = COLOR_BLUE } })

Uses Clay_BorderElementConfig. Configures the element as a border element, which instructs the renderer to draw coloured border lines along the perimeter of this element's bounding box. Causes a render command with type BORDER to be emitted.

.userData - void *

CLAY({ .userData = &extraData })

Transparently passes a pointer through to the corresponding Clay_RenderCommandss generated by this element.

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(rectangleConfig)) {}
// Declare a retangle element using an inline config
CLAY({ .color = { 200, 200, 100, 255 }, .cornerRadius = CLAY_CORNER_RADIUS(10) })) {
    // child elements
}
// Declare a scrolling container with a colored background
CLAY({ 
    .backgroundColor = { 200, 200, 100, 255 }, 
    .cornerRadius = CLAY_CORNER_RADIUS(10)
    .clip = { .vertical = true, .childOffset = Clay_GetScrollOffset() }
) {
    // child elements
}

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.

Clay_LayoutConfig

Clay_LayoutConfig 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 = { ...fields } }) supports these options
Clay_LayoutConfig {
    Clay_LayoutDirection layoutDirection = CLAY_LEFT_TO_RIGHT (default) | CLAY_TOP_TO_BOTTOM;
    Clay_Padding padding {
        u16 left; u16 right; u16 top; u16 bottom; 
    };
    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(float 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(float height) | CLAY_SIZING_PERCENT(float percent)
    }; // See CLAY_SIZING_GROW() etc for more details
};

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 = { .left = 16, .right = 16, .top = 8, .bottom = 8 } } })

Controls 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({ .id = CLAY_ID("Button"), .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM, .sizing = { .width = CLAY_SIZING_GROW(0) }, .padding = CLAY_PADDING_ALL(16, .childGap = 16) } }) {
    // Children will be laid out vertically with 16px of padding around and between
}

Clay_ImageElementConfig

Usage

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

Clay_ImageElementConfig configures a clay element to render an image as its background.

Struct API (Pseudocode)

Clay_ImageElementConfig {
    Clay_Dimensions sourceDimensions {
        float width; float height; 
    };
    void * imageData;
};

Fields

.sourceDimensions - Clay_Dimensions

CLAY({ .image = { .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 = { .imageData = &myImage } }) {}

.imageData is a generic void pointer that can be used to pass through image data to the renderer.

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

Examples

// Load an image somewhere in your code
YourImage profilePicture = LoadYourImage("profilePicture.png");
// Declare a reusable image config
Clay_ImageElementConfig imageConfig = (Clay_ImageElementConfig) { .imageData = &profilePicture, .sourceDimensions = {60, 60} };
// Declare an image element using a reusable config
CLAY({ .image = imageConfig }) {}
// Declare an image element using an inline config
CLAY({ .image = { .imageData = &profilePicture, .sourceDimensions = {60, 60} } }) {}
// Rendering example
YourImage *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->renderData.image->imageData to retrieve image data referenced during layout creation. It's also up to the user to decide how / if they wish to blend renderCommand->renderData.image->backgroundColor with the image.

Clay_ClipElementConfig

Usage

CLAY({ .clip = { ...clip config } }) {}

Notes

Clay_ClipElementConfig configures the element as a clipping container, enabling masking of children that extend beyond its boundaries.

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_ClipElementConfig {
    bool horizontal;
    bool vertical;
};

Fields

.horizontal - bool

CLAY({ .clip = { .horizontal = true } })

Enables or disables horizontal clipping for this container element.

.vertical - bool

CLAY({ .clip = { .vertical = true } })

Enables or disables vertical clipping for this container element.

Rendering

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

Clay_BorderElementConfig

Usage

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

Notes

Clay_BorderElementConfig 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_Color color {
        float r; float g; float b; float a;
    };
    Clay_BorderWidth width {
        uint16_t left;
        uint16_t right;
        uint16_t top;
        uint16_t bottom;
        uint16_t betweenChildren;  
    };
} Clay_BorderElementConfig;

Fields

.color - Clay_Color

CLAY({ .border = { .color = { 255, 0, 0, 255 } } })

Uses Clay_Color. Specifies the shared color for all borders configured by this element. Conventionally accepts rgba float values between 0 and 255, but interpretation is left up to the renderer and does not affect layout.

.width - Clay_BorderWidth

CLAY({ .border = { .width = { .left = 2, .right = 10 } } })

Indicates to the renderer that a border of .color should be draw at the specified edges of the bounding box, inset and 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.

Note:

.width.betweenChildren

CLAY({ .border = { .width = { .betweenChildren = 2 } }, .color = 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.

Examples

// 300x300 container with a 1px red border around all the edges
CLAY({
    .id = CLAY_ID("OuterBorder"),
    .layout = { .sizing = { .width = CLAY_SIZING_FIXED(300), .height = CLAY_SIZING_FIXED(300) } },
    .border = { .width = { 1, 1, 1, 1, 0 }, .color = COLOR_RED }
}) {
    // ...
}

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

// Container with a 5px curved border around the edges, and a 5px blue border between all children laid out top to bottom
CLAY({
    .id = CLAY_ID("OuterBorder"),
    .layout = { .layoutDirection = CLAY_TOP_TO_BOTTOM },
    .border = { .width = { 5, 5, 5, 5, 5 }, .color = COLOR_BLUE }
}) {
    // 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_FloatingElementConfig

Usage

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

Notes

Floating Elements 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 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
    };
    uint32_t parentId;
    int16_t zIndex;
    Clay_FloatingAttachPoints attachPoint {
        .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_FloatingAttachToElement attachTo {
        CLAY_POINTER_CAPTURE_MODE_CAPTURE (default),
        CLAY_POINTER_CAPTURE_MODE_PASSTHROUGH
    };
    Clay_FloatingAttachToElement attachTo {
        CLAY_ATTACH_TO_NONE (default),
        CLAY_ATTACH_TO_PARENT,
        CLAY_ATTACH_TO_ELEMENT_WITH_ID,
        CLAY_ATTACH_TO_ROOT,
    };
};

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({ .id = CLAY_IDI("SidebarButton", 1) }) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 1) {
        CLAY({ /* floating config... */ })
    }
}
CLAY({ .id = CLAY_IDI("SidebarButton", 2) }) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 2) {
        CLAY({ /* floating config... */ })
    }
}
CLAY({ .id = CLAY_IDI("SidebarButton", 3) }) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 3) {
        CLAY({ /* floating config... */ })
    }
}
CLAY({ .id = CLAY_IDI("SidebarButton", 4) }) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 4) {
        CLAY({ /* floating config... */ })
    }
}
CLAY({ .id = CLAY_IDI("SidebarButton", 5) }) {
    // .. some button contents
    if (tooltip.attachedButtonIndex == 5) {
        CLAY({ /* 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({ .id = CLAY_IDI("SidebarButton", 1) }) {
    // .. some button contents
}
CLAY({ .id = CLAY_IDI("SidebarButton", 2) }) {
    // .. some button contents
}
CLAY({ .id = CLAY_IDI("SidebarButton", 3) }) {
    // .. some button contents
}
CLAY({ .id = CLAY_IDI("SidebarButton", 4) }) {
    // .. some button contents
}
CLAY({ .id = CLAY_IDI("SidebarButton", 5) }) {
    // .. some button contents
}

// Any other point in the hierarchy
CLAY({ .id = CLAY_ID("OptionTooltip"), .floating = { .attachTo = CLAY_ATTACH_TO_ELEMENT_ID, .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({ .id = CLAY_ID("OptionsList"), .layout = { childGap = 16 } }) {
    CLAY({ .id = CLAY_IDI("Option", 1), .layout = { padding = CLAY_PADDING_ALL(16)), .backgroundColor = COLOR_BLUE } }) {
        CLAY_TEXT(CLAY_STRING("Option 1"), CLAY_TEXT_CONFIG());
    }
    CLAY({ .id = CLAY_IDI("Option", 2), .layout = { padding = CLAY_PADDING_ALL(16)), .backgroundColor = COLOR_BLUE } }) {
        CLAY_TEXT(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({ .id = CLAY_ID("OptionTooltip"), .floating = { .zIndex = 1, .attachment = { .element = CLAY_ATTACH_POINT_CENTER_BOTTOM, .parent = CLAY_ATTACH_POINT_CENTER_TOP } } }) {
            CLAY_TEXT(CLAY_STRING("Most popular!"), CLAY_TEXT_CONFIG());
        }
    }
    CLAY({ .id = CLAY_IDI("Option", 3), .layout = { padding = CLAY_PADDING_ALL(16)), .backgroundColor = COLOR_BLUE } }) {
        CLAY_TEXT(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({ .id = CLAY_IDI("Option", i + 1) }) {
        // ...
    }
}
// Note the use of "parentId".
// Floating tooltip will attach above the "Option 2" container and not affect widths or positions of other elements
CLAY({ .id = CLAY_ID("OptionTooltip"), .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_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_FloatingElementConfig is used.

Rendering

Clay_FloatingElementConfig will not generate any specific render commands.

Clay_CustomElementConfig

Usage

CLAY({ .custom = { .customData = &something } }) {}

Notes

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

Struct Definition (Pseudocode)

typedef struct
{
    void * customData;
} Clay_CustomElementConfig;

Fields

.customData - void *

CLAY({ .custom = { .customData = &myCustomData } })

.customData is a generic void pointer that can be used to pass through custom data to the renderer.

Examples

#include "clay.h"

typedef enum {
    CUSTOM_ELEMENT_TYPE_MODEL,
    CUSTOM_ELEMENT_TYPE_VIDEO
} CustomElementType;

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

Model myModel = Load3DModel(filePath);
CustomElement modelElement = (CustomElement) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel }

typedef struct {
    void* memory;
    uintptr_t offset;
} Arena;

// During init
Arena frameArena = (Arena) { .memory = malloc(1024) };

// ...
CLAY(0) {
    // Custom elements only take a single pointer, so we need to store the data somewhere
    CustomElementData *modelData = (CustomElementData *)(frameArena.memory + frameArena.offset);
    *modelData = (CustomElementData) { .type = CUSTOM_ELEMENT_TYPE_MODEL, .model = myModel };
    frameArena.offset += sizeof(CustomElementData);
    CLAY({ .custom = { .customData = modelData } }) {}
}

// 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;
    }
}

Rendering

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

Clay_Color

typedef struct {
    float r, g, b, a;
} Clay_Color;

Clay_Color is an RGBA color struct used in Clay's declarations and rendering. By convention the channels are represented as 0-255, but this is left up to the renderer. Note: when using the debug tools, their internal colors are represented as 0-255.

Clay_String

typedef struct {
    bool isStaticallyAllocated;
    int32_t length;
    const char *chars;
} Clay_String;

Clay_String is a string container that clay uses internally to represent all strings.

Fields

.isStaticallyAllocated - bool

Whether or not the string is statically allocated, or in other words, whether or not it lives for the entire lifetime of the program.

.length - int32_t

The number of characters in the string, not including an optional null terminator.

.chars - const char *

A pointer to the contents of the string. This data is not guaranteed to be null terminated, so if you are passing it to code that expects standard null terminated C strings, you will need to copy the data and append a null terminator.

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_RenderData renderData;
    uintptr_t userData;
    uint32_t id;
    int16_t zIndex;
    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.

.id - uint32_t

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

.zIndex - int16_t

The z index of the element, based on what was passed to the root floating configuration that this element is a child of. Higher z indexes should be rendered on top of lower z indexes.

.renderData - Clay_RenderData

typedef union {
    Clay_RectangleRenderData rectangle;
    Clay_TextRenderData text;
    Clay_ImageRenderData image;
    Clay_CustomRenderData custom;
    Clay_BorderRenderData border;
} Clay_RenderData;

A C union containing various structs, with the type dependent on .commandType. Possible values include:

config.rectangle - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_RECTANGLE.
config.text - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_TEXT. See Clay_Text for details.
config.image - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_IMAGE. See Clay_Image for details.
config.border - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_BORDER. See Clay_Border for details.
config.custom - Used when .commandType == CLAY_RENDER_COMMAND_TYPE_CUSTOM. See Clay_Custom for details.

Union Structs

typedef struct {
    Clay_StringSlice stringContents;
    Clay_Color textColor;
    uint16_t fontId;
    uint16_t fontSize;
    uint16_t letterSpacing;
    uint16_t lineHeight;
} Clay_TextRenderData;

typedef struct {
    Clay_Color backgroundColor;
    Clay_CornerRadius cornerRadius;
} Clay_RectangleRenderData;

typedef struct {
    Clay_Color backgroundColor;
    Clay_CornerRadius cornerRadius;
    Clay_Dimensions sourceDimensions;
    void* imageData;
} Clay_ImageRenderData;

typedef struct {
    Clay_Color backgroundColor;
    Clay_CornerRadius cornerRadius;
    void* customData;
} Clay_CustomRenderData;

typedef struct {
    Clay_Color color;
    Clay_CornerRadius cornerRadius;
    Clay_BorderWidth width;
} Clay_BorderRenderData;

typedef union {
    Clay_RectangleRenderData rectangle;
    Clay_TextRenderData text;
    Clay_ImageRenderData image;
    Clay_CustomRenderData custom;
    Clay_BorderRenderData border;
} Clay_RenderData;

Clay_ScrollContainerData

// Data representing the current internal state of a scrolling element.
typedef struct {
    // Note: This is a pointer to the real internal scroll position, mutating it may cause a change in final layout.
    // Intended for use with external functionality that modifies scroll position, such as scroll bars or auto scrolling.
    Clay_Vector2 *scrollPosition;
    // The bounding box of the scroll element.
    Clay_Dimensions scrollContainerDimensions;
    // The outer dimensions of the inner scroll container content, including the padding of the parent scroll container.
    Clay_Dimensions contentDimensions;
    // The config that was originally passed to the scroll element.
    Clay_ClipElementConfig config;
    // Indicates whether an actual scroll container matched the provided ID or if the default struct was returned.
    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_ClipElementConfig

The Clay_ClipElementConfig for the matching scroll container element.

Clay_ElementData

// Bounding box and other data for a specific UI element.
typedef struct {
    // The rectangle that encloses this UI element, with the position relative to the root of the layout.
    Clay_BoundingBox boundingBox;
    // Indicates whether an actual Element matched the provided ID or if the default struct was returned.
    bool found;
} Clay_ElementData;

Fields

.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.

.found - bool

A boolean representing whether or not the ID passed to Clay_GetElementData matched a valid element or not. In the case that .found is false, .boundingBox will be the default value (zeroed).

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

Clay_ErrorHandler

typedef struct
{
    void (*errorHandlerFunction)(Clay_ErrorData errorText);
    uintptr_t userData;
} Clay_ErrorHandler;

Fields

.errorHandlerFunction - void (Clay_ErrorData errorText) {}

A function pointer to an error handler function, which takes Clay_ErrorData as an argument. This function will be called whenever Clay encounters an internal error.

.userData - uintptr_t

A generic pointer to extra userdata that is transparently passed through from Clay_Initialize to Clay's error handler callback. Defaults to NULL.

Clay_ErrorData

typedef struct
{
    Clay_ErrorType errorType;
    Clay_String errorText;
    uintptr_t userData;
} Clay_ErrorData;

Fields

.errorType - Clay_ErrorType

typedef enum {
    CLAY_ERROR_TYPE_TEXT_MEASUREMENT_FUNCTION_NOT_PROVIDED,
    CLAY_ERROR_TYPE_ARENA_CAPACITY_EXCEEDED,
    CLAY_ERROR_TYPE_ELEMENTS_CAPACITY_EXCEEDED,
    CLAY_ERROR_TYPE_TEXT_MEASUREMENT_CAPACITY_EXCEEDED,
    CLAY_ERROR_TYPE_DUPLICATE_ID,
    CLAY_ERROR_TYPE_FLOATING_CONTAINER_PARENT_NOT_FOUND,
    CLAY_ERROR_TYPE_INTERNAL_ERROR,
} Clay_ErrorType;

An enum representing the type of error Clay encountered. It's up to the user to handle on a case by case basis, but as some general guidance:

CLAY_ERROR_TYPE_TEXT_MEASUREMENT_FUNCTION_NOT_PROVIDED - The user is attempting to use CLAY_TEXT and either forgot to call Clay_SetMeasureTextFunction or accidentally passed a null function pointer.
CLAY_ERROR_TYPE_ARENA_CAPACITY_EXCEEDED - Clay was initialized with an Arena that was too small for the configured Clay_SetMaxElementCount. Try using Clay_MinMemorySize() to get the exact number of bytes required by the current configuration.
CLAY_ERROR_TYPE_ELEMENTS_CAPACITY_EXCEEDED - The declared UI hierarchy has too many elements for the configured max element count. Use Clay_SetMaxElementCount to increase the max, then call Clay_MinMemorySize() again and reinitialize clay's memory with the required size.
CLAY_ERROR_TYPE_ELEMENTS_CAPACITY_EXCEEDED - The declared UI hierarchy has too much text for the configured text measure cache size. Use Clay_SetMaxMeasureTextCacheWordCount to increase the max, then call Clay_MinMemorySize() again and reinitialize clay's memory with the required size.
CLAY_ERROR_TYPE_DUPLICATE_ID - Two elements in Clays UI Hierarchy have been declared with exactly the same ID. Set a breakpoint in your error handler function for a stack trace back to exactly where this occured.
CLAY_ERROR_TYPE_FLOATING_CONTAINER_PARENT_NOT_FOUND - A CLAY_FLOATING element was declared with the .parentId property, but no element with that ID was found. Set a breakpoint in your error handler function for a stack trace back to exactly where this occured.
CLAY_ERROR_TYPE_INTERNAL_ERROR - Clay has encountered an internal logic or memory error. Please report this as a bug with a stack trace to help us fix these!

.errorText - Clay_String

A Clay_String that provides a human readable description of the error. May change in future and should not be relied on to detect error types.

.userData - uintptr_t

A generic pointer to extra userdata that is transparently passed through from Clay_Initialize to Clay's error handler callback. Defaults to NULL.

License

swordlib/clay

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