initial

test.c

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+/* -------------------------------------------------------------
+ * framebuffer_demo.c
+ * -------------------------------------------------------------
+ * A tiny example that:
+ *   * allocates a 600×400 RGB‑888 framebuffer in RAM,
+ *   * fills it with a demo pattern,
+ *   * opens an SDL2 window,
+ *   * streams the framebuffer to the window each frame.
+ *
+ * Build (Linux/macOS):
+ *   gcc -Wall -O2 -std=c11 framebuffer_demo.c -lSDL2 -o framebuffer_demo
+ *
+ * Run:
+ *   ./framebuffer_demo
+ *
+ * ------------------------------------------------------------- */
+#include <SDL2/SDL.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+/* -------------------------------------------------------------
+ * Configuration
+ * ------------------------------------------------------------- */
+#define WIDTH   600
+#define HEIGHT  400
+
+/* -------------------------------------------------------------
+ * Simple pixel format helpers
+ * ------------------------------------------------------------- */
+/* The framebuffer will be stored as 32‑bit ARGB (0xAARRGGBB). */
+typedef Uint32 pixel_t;
+
+/* Build a pixel from separate components (no gamma correction). */
+static inline pixel_t make_pixel(Uint8 r, Uint8 g, Uint8 b, Uint8 a) {
+    /* SDL uses little‑endian, so the order in memory is BGRA.
+     * Our 0xAARRGGBB layout works fine with SDL_UpdateTexture. */
+    return (pixel_t)( (a << 24) | (r << 16) | (g << 8) | b );
+}
+
+/* -------------------------------------------------------------
+ * Global framebuffer
+ * ------------------------------------------------------------- */
+static pixel_t framebuffer[HEIGHT][WIDTH];
+
+/* -------------------------------------------------------------
+ * Fill the framebuffer with a demo pattern
+ * ------------------------------------------------------------- */
+static void init_framebuffer(void)
+{
+    for (int y = 0; y < HEIGHT; ++y) {
+        for (int x = 0; x < WIDTH; ++x) {
+            /* Example: a smooth red‑to‑green gradient */
+            Uint8 r = (Uint8)((x * 255) / (WIDTH - 1));   /* left → right */
+            Uint8 g = (Uint8)((y * 255) / (HEIGHT - 1));  /* top → bottom */
+            Uint8 b = 0x80;                               /* constant bluish */
+            framebuffer[y][x] = make_pixel(r, g, b, 255);
+        }
+    }
+}
+
+/* -------------------------------------------------------------
+ * Main entry point
+ * ------------------------------------------------------------- */
+int main(void)
+{
+    if (SDL_Init(SDL_INIT_VIDEO) != 0) {
+        fprintf(stderr, "SDL_Init error: %s\n", SDL_GetError());
+        return EXIT_FAILURE;
+    }
+
+    /* ---------------------------------------------------------
+     * Create a window and a renderer (software accelerated is fine)
+     * --------------------------------------------------------- */
+    SDL_Window *window = SDL_CreateWindow(
+        "Framebuffer Demo",
+        SDL_WINDOWPOS_CENTERED,
+        SDL_WINDOWPOS_CENTERED,
+        WIDTH,
+        HEIGHT,
+        SDL_WINDOW_SHOWN
+    );
+    if (!window) {
+        fprintf(stderr, "SDL_CreateWindow error: %s\n", SDL_GetError());
+        SDL_Quit();
+        return EXIT_FAILURE;
+    }
+
+    SDL_Renderer *renderer = SDL_CreateRenderer(
+        window,
+        -1,
+        SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC
+    );
+    if (!renderer) {
+        fprintf(stderr, "SDL_CreateRenderer error: %s\n", SDL_GetError());
+        SDL_DestroyWindow(window);
+        SDL_Quit();
+        return EXIT_FAILURE;
+    }
+
+    /* ---------------------------------------------------------
+     * Create a texture that will hold the framebuffer.
+     * SDL_PIXELFORMAT_ARGB8888 matches our pixel_t layout.
+     * --------------------------------------------------------- */
+    SDL_Texture *texture = SDL_CreateTexture(
+        renderer,
+        SDL_PIXELFORMAT_ARGB8888,
+        SDL_TEXTUREACCESS_STREAMING,
+        WIDTH,
+        HEIGHT
+    );
+    if (!texture) {
+        fprintf(stderr, "SDL_CreateTexture error: %s\n", SDL_GetError());
+        SDL_DestroyRenderer(renderer);
+        SDL_DestroyWindow(window);
+        SDL_Quit();
+        return EXIT_FAILURE;
+    }
+
+    /* ---------------------------------------------------------
+     * Initialise the framebuffer with example data.
+     * --------------------------------------------------------- */
+    init_framebuffer();
+
+    /* ---------------------------------------------------------
+     * Main loop
+     * --------------------------------------------------------- */
+    bool quit = false;
+    SDL_Event ev;
+
+    while (!quit) {
+        /* ----- Event handling --------------------------------- */
+        while (SDL_PollEvent(&ev)) {
+            if (ev.type == SDL_QUIT) {
+                quit = true;
+            } else if (ev.type == SDL_KEYDOWN) {
+                /* Press Escape to quit */
+                if (ev.key.keysym.sym == SDLK_ESCAPE)
+                    quit = true;
+            }
+        }
+
+        /* ----- Update texture from the framebuffer ------------ */
+        void *tex_pixels;
+        int   tex_pitch;   // bytes per row
+        if (SDL_LockTexture(texture, NULL, &tex_pixels, &tex_pitch) != 0) {
+            fprintf(stderr, "SDL_LockTexture error: %s\n", SDL_GetError());
+            break;
+        }
+
+        /* Copy line‑by‑line because the pitch may differ from WIDTH*4 */
+        for (int y = 0; y < HEIGHT; ++y) {
+            memcpy(
+                (Uint8 *)tex_pixels + y * tex_pitch,
+                framebuffer[y],
+                WIDTH * sizeof(pixel_t)
+            );
+        }
+        SDL_UnlockTexture(texture);
+
+        /* ----- Render ------------------------------------------ */
+        SDL_RenderClear(renderer);
+        SDL_RenderCopy(renderer, texture, NULL, NULL);
+        SDL_RenderPresent(renderer);
+        /* The loop runs at the monitor refresh rate thanks to VSYNC. */
+    }
+
+    /* ---------------------------------------------------------
+     * Cleanup
+     * --------------------------------------------------------- */
+    SDL_DestroyTexture(texture);
+    SDL_DestroyRenderer(renderer);
+    SDL_DestroyWindow(window);
+    SDL_Quit();
+
+    return EXIT_SUCCESS;
+}