Custom pixel buffer

build

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+clang -g -Og -lSDL2 main.c -o main

main.c

@@ -0,0 +1,125 @@
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_events.h>
+#include <SDL2/SDL_rect.h>
+#include <SDL2/SDL_render.h>
+#include <SDL2/SDL_surface.h>
+#include <SDL2/SDL_video.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <string.h>
+
+#define WINDOW_WIDTH 800
+#define WINDOW_HEIGHT 600
+
+#define SURFACE_WIDTH 780
+#define SURFACE_HEIGHT 580
+
+#define RMASK 0xff000000
+#define GMASK 0x00ff0000
+#define BMASK 0x0000ff00
+#define AMASK 0x000000ff
+
+#define WHITE 0xff
+
+typedef struct {
+  uint32_t x;
+  uint32_t y;
+} coord_t;
+
+coord_t coord_from_index(uint32_t index, uint32_t w);
+
+int main(void) {
+  SDL_Init(SDL_INIT_EVERYTHING);
+
+  SDL_Window *window =
+      SDL_CreateWindow("Window", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED,
+                       WINDOW_WIDTH, WINDOW_HEIGHT, SDL_WINDOW_SHOWN);
+
+  SDL_Renderer *renderer = SDL_CreateRenderer(
+      window, -1, SDL_RENDERER_ACCELERATED | SDL_RENDERER_PRESENTVSYNC);
+
+  bool running = true;
+
+  SDL_Event event = {0};
+
+  SDL_Surface *surface = SDL_CreateRGBSurface(0, SURFACE_WIDTH, SURFACE_HEIGHT,
+                                              32, RMASK, GMASK, BMASK, AMASK);
+
+  uint64_t length = surface->h * surface->pitch;
+
+  uint32_t pixels[length];
+  memset(pixels, 0, length);
+
+  coord_t coord = {0};
+
+  uint8_t x = 0;
+  uint8_t y = 0;
+  uint32_t c = 0;
+
+  for (uint64_t i = 0; i < length; ++i) {
+    coord = coord_from_index(i, surface->w);
+
+    x = ((float)coord.x / surface->w) * WHITE;
+    y = ((float)coord.y / surface->h) * WHITE;
+
+    // clang-format off
+    c = (((uint32_t)x) << surface->format->Rshift) |
+        (((uint32_t)y) << surface->format->Gshift) |
+				AMASK;
+    // clang-format on
+
+    pixels[i] = c;
+  }
+
+  SDL_LockSurface(surface);
+
+  surface->pixels = (void *)pixels;
+
+  SDL_UnlockSurface(surface);
+
+  SDL_Texture *texture = SDL_CreateTextureFromSurface(renderer, surface);
+
+  SDL_Rect dest = {
+      .w = surface->w,
+      .h = surface->h,
+      .x = (WINDOW_WIDTH - surface->w) / 2,
+      .y = (WINDOW_HEIGHT - surface->h) / 2,
+  };
+
+  while (running) {
+    while (SDL_PollEvent(&event)) {
+      switch (event.type) {
+      case SDL_QUIT:
+        running = false;
+        break;
+      }
+    }
+
+    SDL_SetRenderDrawColor(renderer, 16, 22, 25, 255);
+
+    SDL_RenderClear(renderer);
+
+    SDL_RenderCopy(renderer, texture, NULL, &dest);
+
+    SDL_RenderPresent(renderer);
+  }
+
+  SDL_DestroyRenderer(renderer);
+
+  SDL_DestroyWindow(window);
+
+  SDL_Quit();
+
+  return 0;
+}
+
+coord_t coord_from_index(uint32_t index, uint32_t w) {
+  coord_t out = {0};
+
+  out.x = index % w;
+
+  out.y = (index - (index % w)) / w;
+
+  return out;
+}