Adds an example using SDL3 as a renderer

This example is rather basic but it does provide an example how one
could setup a rendering loop between clay and SDL3.

Although SDL3 is in its infancy and doesn't have an official stable
release the API has been locked so there shouldn't be any code
adaptations required for this example if one was to update to a more
recent SDL3 release in the future.

examples/sdl3_renderer/CMakeLists.txt

@@ -0,0 +1,47 @@
+cmake_minimum_required(VERSION 3.27)
+
+# Project setup
+project(clay_sdl3_renderer C)
+set(CMAKE_C_FLAGS_DEBUG "-g -Wall -Werror")
+set(CMAKE_C_FLAGS_RELEASE "-O3")
+
+include(FetchContent)
+set(FETCHCONTENT_QUIET FALSE)
+
+# Download SDL3
+FetchContent_Declare(
+	SDL
+	GIT_REPOSITORY https://github.com/libsdl-org/SDL.git
+	GIT_TAG preview-3.1.6
+	GIT_SHALLOW TRUE
+	GIT_PROGRESS TRUE
+)
+message(STATUS "Using SDL via FetchContent")
+FetchContent_MakeAvailable(SDL)
+set_property(DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/_deps/sdl-src" PROPERTY EXCLUDE_FROM_ALL TRUE)
+
+# Download SDL_ttf
+FetchContent_Declare(
+	SDL_ttf
+	GIT_REPOSITORY https://github.com/libsdl-org/SDL_ttf.git
+	GIT_TAG 40219a6
+	GIT_SHALLOW TRUE
+	GIT_PROGRESS TRUE
+)
+message(STATUS "Using SDL_ttf via FetchContent")
+FetchContent_MakeAvailable(SDL_ttf)
+set_property(DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/_deps/sdl_ttf-src" PROPERTY EXCLUDE_FROM_ALL TRUE)
+
+# Example executable
+add_executable(${PROJECT_NAME} main.c)
+target_link_libraries(${PROJECT_NAME} PRIVATE
+	SDL3::SDL3
+	SDL3_ttf::SDL3_ttf
+)
+
+add_custom_command(
+	TARGET ${PROJECT_NAME} POST_BUILD
+	COMMAND ${CMAKE_COMMAND} -E copy_directory
+		${CMAKE_CURRENT_SOURCE_DIR}/resources
+		${CMAKE_CURRENT_BINARY_DIR}/resources
+)

examples/sdl3_renderer/main.c

@@ -0,0 +1,215 @@
+#define SDL_MAIN_USE_CALLBACKS
+#include <SDL3/SDL_main.h>
+#include <SDL3/SDL.h>
+#include <SDL3_ttf/SDL_ttf.h>
+
+#define CLAY_IMPLEMENTATION
+#include "../../clay.h"
+
+static const Uint32 FONT_ID = 0;
+
+static const Clay_Color COLOR_ORANGE    = (Clay_Color) {225, 138, 50, 255};
+static const Clay_Color COLOR_BLUE      = (Clay_Color) {111, 173, 162, 255};
+static const Clay_Color COLOR_LIGHT     = (Clay_Color) {224, 215, 210, 255};
+
+typedef struct app_state {
+    SDL_Window *window;
+    SDL_Renderer *renderer;
+} AppState;
+
+/* This needs to be global because the "MeasureText" callback doesn't have a
+ * user data parameter */
+static TTF_Font *gFonts[1];
+
+static inline Clay_Dimensions SDL_MeasureText(Clay_String *text, Clay_TextElementConfig *config)
+{
+    TTF_Font *font = gFonts[config->fontId];
+    int width, height;
+
+    if (!TTF_GetStringSize(font, text->chars, text->length, &width, &height)) {
+        SDL_LogError(SDL_LOG_CATEGORY_ERROR, "Failed to measure text: %s", SDL_GetError());
+    }
+
+    return (Clay_Dimensions) { (float) width, (float) height };
+}
+
+static void Label(Clay_String text)
+{
+    CLAY(CLAY_LAYOUT({ .padding = {16, 8} }), CLAY_RECTANGLE({ .color = Clay_Hovered() ? COLOR_BLUE : COLOR_ORANGE })) {
+        CLAY_TEXT(text, CLAY_TEXT_CONFIG({
+           .textColor = { 255, 255, 255, 255 },
+           .fontId = FONT_ID,
+           .fontSize = 24,
+        }));
+   }
+}
+
+static Clay_RenderCommandArray Clay_CreateLayout()
+{
+    Clay_BeginLayout();
+    CLAY(CLAY_ID("MainContent"),
+        CLAY_LAYOUT({
+            .sizing = {
+                .width = CLAY_SIZING_GROW(),
+                .height = CLAY_SIZING_GROW(),
+            },
+            .childAlignment = {
+                .x = CLAY_ALIGN_X_CENTER,
+                .y = CLAY_ALIGN_Y_CENTER,
+            },
+            .childGap = 10,
+            .padding = { 10, 10 },
+            .layoutDirection = CLAY_TOP_TO_BOTTOM,
+        }),
+        CLAY_RECTANGLE({
+            .color = COLOR_LIGHT,
+        })
+    ) {
+        Label(CLAY_STRING("Button 1"));
+        Label(CLAY_STRING("Button 2"));
+        Label(CLAY_STRING("Button 3"));
+    }
+    return Clay_EndLayout();
+}
+
+static void SDL_RenderClayCommands(SDL_Renderer *renderer, Clay_RenderCommandArray *rcommands)
+{
+    for (size_t i = 0; i < rcommands->length; i++) {
+        Clay_RenderCommand *rcmd = Clay_RenderCommandArray_Get(rcommands, i);
+        Clay_BoundingBox bounding_box = rcmd->boundingBox;
+        SDL_FRect rect = { bounding_box.x, bounding_box.y, bounding_box.width, bounding_box.height };
+
+        switch (rcmd->commandType) {
+            case CLAY_RENDER_COMMAND_TYPE_RECTANGLE: {
+                Clay_RectangleElementConfig *config = rcmd->config.rectangleElementConfig;
+                Clay_Color color = config->color;
+                SDL_SetRenderDrawColor(renderer, color.r, color.g, color.b, color.a);
+                SDL_RenderFillRect(renderer, &rect);
+            } break;
+            case CLAY_RENDER_COMMAND_TYPE_TEXT: {
+                Clay_TextElementConfig *config = rcmd->config.textElementConfig;
+                Clay_String *text = &rcmd->text;
+                SDL_Color color = { config->textColor.r, config->textColor.g, config->textColor.b, config->textColor.a };
+
+                TTF_Font *font = gFonts[config->fontId];
+                SDL_Surface *surface = TTF_RenderText_Blended(font, text->chars, text->length, color);
+                SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, surface);
+                SDL_RenderTexture(renderer, texture, NULL, &rect);
+
+                SDL_DestroySurface(surface);
+                SDL_DestroyTexture(texture);
+            } break;
+            default:
+                SDL_Log("Unknown render command type: %d", rcmd->commandType);
+        }
+    }
+}
+
+SDL_AppResult SDL_AppInit(void **appstate, int argc, char *argv[])
+{
+    (void) argc;
+    (void) argv;
+
+    if (!TTF_Init()) {
+        return SDL_APP_FAILURE;
+    }
+
+    AppState *state = SDL_calloc(1, sizeof(AppState));
+    if (!state) {
+        return SDL_APP_FAILURE;
+    }
+    *appstate = state;
+
+    if (!SDL_CreateWindowAndRenderer("Clay Demo", 640, 480, 0, &state->window, &state->renderer)) {
+        SDL_LogError(SDL_LOG_CATEGORY_ERROR, "Failed to create window and renderer: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+    SDL_SetWindowResizable(state->window, true);
+
+    TTF_Font *font = TTF_OpenFont("resources/Roboto-Regular.ttf", 24);
+    if (!font) {
+        SDL_LogError(SDL_LOG_CATEGORY_ERROR, "Failed to load font: %s", SDL_GetError());
+        return SDL_APP_FAILURE;
+    }
+
+    gFonts[FONT_ID] = font;
+
+    /* Initialize Clay */
+    uint64_t totalMemorySize = Clay_MinMemorySize();
+    Clay_Arena clayMemory = (Clay_Arena) {
+        .label = CLAY_STRING("Clay Memory Arena"),
+        .memory = SDL_malloc(totalMemorySize),
+        .capacity = totalMemorySize
+    };
+
+    int width, height;
+    SDL_GetWindowSize(state->window, &width, &height);
+    Clay_SetMeasureTextFunction(SDL_MeasureText);
+    Clay_Initialize(clayMemory, (Clay_Dimensions) { (float) width, (float) height });
+
+    *appstate = state;
+    return SDL_APP_CONTINUE;
+}
+
+SDL_AppResult SDL_AppEvent(void *appstate, SDL_Event *event)
+{
+    SDL_AppResult ret_val = SDL_APP_CONTINUE;
+
+    switch (event->type) {
+        case SDL_EVENT_QUIT:
+            ret_val = SDL_APP_SUCCESS;
+            break;
+        case SDL_EVENT_WINDOW_RESIZED:
+            Clay_SetLayoutDimensions((Clay_Dimensions) { (float) event->window.data1, (float) event->window.data2 });
+            break;
+        case SDL_EVENT_MOUSE_MOTION:
+            Clay_SetPointerState((Clay_Vector2) { event->motion.x, event->motion.y },
+                                 event->motion.state & SDL_BUTTON_LEFT);
+            break;
+        case SDL_EVENT_MOUSE_WHEEL:
+            Clay_UpdateScrollContainers(true, (Clay_Vector2) { event->motion.xrel, event->motion.yrel }, 0.01f);
+            break;
+        default:
+            break;
+    };
+
+    return ret_val;
+}
+
+SDL_AppResult SDL_AppIterate(void *appstate)
+{
+    AppState *state = appstate;
+
+    Clay_RenderCommandArray render_commands = Clay_CreateLayout();
+
+    SDL_SetRenderDrawColor(state->renderer, 0, 0, 0, 255);
+    SDL_RenderClear(state->renderer);
+
+    SDL_RenderClayCommands(state->renderer, &render_commands);
+
+    SDL_RenderPresent(state->renderer);
+
+    return SDL_APP_CONTINUE;
+}
+
+void SDL_AppQuit(void *appstate, SDL_AppResult result)
+{
+    (void) result;
+
+    if (result != SDL_APP_SUCCESS) {
+        SDL_LogError(SDL_LOG_CATEGORY_ERROR, "Application failed to run");
+    }
+
+    AppState *state = appstate;
+
+    if (state) {
+        if (state->renderer)
+            SDL_DestroyRenderer(state->renderer);
+
+        if (state->window)
+            SDL_DestroyWindow(state->window);
+
+        SDL_free(state);
+    }
+    TTF_Quit();
+}