examples: add sdl2 and pigpio

examples/gpio_sdl/BUILD

@@ -0,0 +1,25 @@
+cc_library(
+    name = "lib",
+    srcs = [
+        "gpio_sdl.cpp",
+    ],
+    hdrs = [
+        "gpio_sdl.h",
+    ],
+    features = ["warnings_critical_code_gcc"],  # Suppress warnings from pigpio.h
+    linkopts = [
+        "-L/lib/x86_64-linux-gnu/include",
+        "-lpigpio",
+        "-lrt",
+        "-lSDL2",
+    ],
+)
+
+cc_binary(
+    name = "bin",
+    srcs = ["main.cpp"],
+    features = ["warnings_critical_code_gcc"],
+    deps = [
+        ":lib",
+    ],
+)

examples/gpio_sdl/README

@@ -0,0 +1,13 @@
+# How to Run
+
+Run the following command to compile for x86:
+
+```bash
+bazel build //examples/gpio_sdl:bin
+```
+
+Run the following command to compile for aarch64:
+
+```bash
+bazel build //examples/gpio_sdl:bin --platforms=//bazel/platforms:aarch64_linux
+```

examples/gpio_sdl/gpio_sdl.cpp

@@ -0,0 +1,44 @@
+#include "gpio_sdl.h"
+#include <pigpio.h>
+#include <iostream>
+
+bool initGPIO() {
+    if (gpioInitialise() < 0) {
+        std::cerr << "Failed to initialize pigpio." << std::endl;
+        return false;
+    }
+    return true;
+}
+
+int readButtonState(int gpioPin) {
+    return gpioRead(static_cast<unsigned int>(gpioPin));
+}
+
+bool initSDL(SDL_Window*& window, SDL_Renderer*& renderer) {
+    if (SDL_Init(SDL_INIT_VIDEO) < 0) {
+        std::cerr << "Failed to initialize SDL: " << SDL_GetError() << std::endl;
+        return false;
+    }
+    window = SDL_CreateWindow("GPIO + SDL2 Example", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 640, 480, SDL_WINDOW_SHOWN);
+    if (!window) {
+        std::cerr << "Failed to create SDL window: " << SDL_GetError() << std::endl;
+        return false;
+    }
+    renderer = SDL_CreateRenderer(window, -1, SDL_RENDERER_ACCELERATED);
+    if (!renderer) {
+        std::cerr << "Failed to create SDL renderer: " << SDL_GetError() << std::endl;
+        SDL_DestroyWindow(window);
+        return false;
+    }
+    return true;
+}
+
+void cleanupSDL(SDL_Window* window, SDL_Renderer* renderer) {
+    SDL_DestroyRenderer(renderer);
+    SDL_DestroyWindow(window);
+    SDL_Quit();
+}
+
+void cleanupGPIO() {
+    gpioTerminate();
+}

examples/gpio_sdl/gpio_sdl.h

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+#ifndef GPIO_SDL_H
+#define GPIO_SDL_H
+
+#include <SDL2/SDL.h>
+
+bool initGPIO();
+int readButtonState(int gpioPin);
+bool initSDL(SDL_Window*& window, SDL_Renderer*& renderer);
+void cleanupSDL(SDL_Window* window, SDL_Renderer* renderer);
+void cleanupGPIO();
+
+#endif  // GPIO_SDL_H

examples/gpio_sdl/main.cpp

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+#include <iostream>
+
+#include <pigpio.h>
+#include "gpio_sdl.h"
+
+#define GPIO_BUTTON 17
+
+int main() {
+    if (!initGPIO()) {
+        return -1;
+    }
+    gpioSetMode(GPIO_BUTTON, PI_INPUT);
+    gpioSetPullUpDown(GPIO_BUTTON, PI_PUD_UP);
+
+    SDL_Window* window = nullptr;
+    SDL_Renderer* renderer = nullptr;
+    if (!initSDL(window, renderer)) {
+        cleanupGPIO();
+        return -1;
+    }
+
+    bool running = true;
+    while (running) {
+        SDL_Event event;
+        while (SDL_PollEvent(&event)) {
+            if (event.type == SDL_QUIT) {
+                running = false;
+            }
+        }
+
+        int buttonState = readButtonState(GPIO_BUTTON);
+
+        SDL_SetRenderDrawColor(renderer, 0, 0, 0, 255);
+        SDL_RenderClear(renderer);
+
+        if (buttonState == 0) {
+            SDL_SetRenderDrawColor(renderer, 0, 255, 0, 255);
+        } else {
+            SDL_SetRenderDrawColor(renderer, 255, 0, 0, 255);
+        }
+        SDL_Rect rect = {220, 140, 200, 200};
+        SDL_RenderFillRect(renderer, &rect);
+
+        SDL_RenderPresent(renderer);
+
+        SDL_Delay(16);
+    }
+
+    cleanupSDL(window, renderer);
+    cleanupGPIO();
+    return 0;
+}