From c836f3758fe52cff7abc822f104d0edc71167569 Mon Sep 17 00:00:00 2001
From: Abdelrahman Said <said.abdelrahman89@gmail.com>
Date: Mon, 18 Dec 2023 13:25:02 +0000
Subject: [PATCH] Implement basic window abstraction

---
 include/window/window.h |  31 +++++++++
 src/window/window.c     | 144 ++++++++++++++++++++++++++++++++++++++++
 2 files changed, 175 insertions(+)
 create mode 100644 include/window/window.h
 create mode 100644 src/window/window.c

diff --git a/include/window/window.h b/include/window/window.h
new file mode 100644
index 0000000..bc99300
--- /dev/null
+++ b/include/window/window.h
@@ -0,0 +1,31 @@
+#ifndef WINDOW_H
+#define WINDOW_H
+
+#include "c_cpp_aliases/aliases.h"
+#include <SDL2/SDL_video.h>
+#include <stdbool.h>
+
+typedef struct {
+  u8 r;
+  u8 g;
+  u8 b;
+  u8 a;
+} colour_t;
+
+typedef struct {
+  u64 width;
+  u64 height;
+  const char *title;
+  SDL_Window *window;
+  SDL_Surface *front_buffer;
+  SDL_Surface *back_buffer;
+} window_t;
+
+bool init_window(window_t *wnd, u64 width, u64 height, const char *title);
+void close_window(window_t *wnd);
+
+void clear_window(window_t *wnd, colour_t colour);
+void set_pixel(window_t *wnd, f32 x, f32 y, colour_t colour);
+void swap_buffers(window_t *wnd);
+
+#endif // !WINDOW_H
diff --git a/src/window/window.c b/src/window/window.c
new file mode 100644
index 0000000..b3f299f
--- /dev/null
+++ b/src/window/window.c
@@ -0,0 +1,144 @@
+#include "window/window.h"
+#include "c_cpp_aliases/aliases.h"
+#include <SDL2/SDL.h>
+#include <SDL2/SDL_error.h>
+#include <SDL2/SDL_pixels.h>
+#include <SDL2/SDL_surface.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#define NORMALISED_MIN -1.0f
+#define NORMALISED_MAX 1.0f
+
+u32 colour_to_u32(colour_t colour);
+u32 index_from_coordinates(window_t *wnd, u32 x, u32 y);
+i32 denormalise(f32 value, u32 max);
+void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour);
+
+bool init_window(window_t *wnd, u64 width, u64 height, const char *title) {
+  if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
+    printf("Failed to initialise SDL: %s\n", SDL_GetError());
+
+    return false;
+  }
+
+  wnd->window = SDL_CreateWindow(title, SDL_WINDOWPOS_CENTERED,
+                                 SDL_WINDOWPOS_CENTERED, width, height, 0);
+  if (!(wnd->window)) {
+    printf("Failed to create window: %s\n", SDL_GetError());
+
+    close_window(wnd);
+
+    return false;
+  }
+
+  wnd->front_buffer = SDL_GetWindowSurface(wnd->window);
+  if (!(wnd->front_buffer)) {
+    printf("Failed to get front buffer: %s\n", SDL_GetError());
+
+    close_window(wnd);
+
+    return false;
+  }
+
+  wnd->back_buffer = SDL_CreateRGBSurfaceWithFormat(0, width, height, 32,
+                                                    SDL_PIXELFORMAT_ABGR32);
+  if (!(wnd->back_buffer)) {
+    printf("Failed to create back buffer: %s\n", SDL_GetError());
+
+    close_window(wnd);
+
+    return false;
+  }
+
+  wnd->width = width;
+  wnd->height = height;
+  wnd->title = title;
+
+  return true;
+}
+
+void close_window(window_t *wnd) {
+  if (wnd) {
+    wnd->width = 0;
+    wnd->height = 0;
+    wnd->title = "";
+
+    if (wnd->window) {
+      SDL_DestroyWindow(wnd->window);
+
+      wnd->window = NULL;
+    }
+
+    if (wnd->back_buffer) {
+      SDL_FreeSurface(wnd->back_buffer);
+
+      wnd->back_buffer = NULL;
+    }
+  }
+
+  SDL_Quit();
+}
+
+void clear_window(window_t *wnd, colour_t colour) {
+  SDL_LockSurface(wnd->back_buffer);
+
+  u32 c = colour_to_u32(colour);
+
+  u32 *pixels = (u32 *)(wnd->back_buffer->pixels);
+  u32 count = wnd->back_buffer->w * wnd->back_buffer->h;
+
+  for (u32 i = 0; i < count; ++i) {
+    pixels[i] = c;
+  }
+
+  SDL_UnlockSurface(wnd->back_buffer);
+}
+
+void set_pixel(window_t *wnd, f32 x, f32 y, colour_t colour) {
+  i32 screen_x = denormalise(x, wnd->width);
+  i32 screen_y = denormalise(-y, wnd->height);
+
+  if (screen_x < 0 || screen_y < 0) {
+    return;
+  }
+
+  SDL_LockSurface(wnd->back_buffer);
+
+  set_screen_pixel(wnd, screen_x, screen_y, colour);
+
+  SDL_UnlockSurface(wnd->back_buffer);
+}
+
+void swap_buffers(window_t *wnd) {
+  SDL_BlitSurface(wnd->back_buffer, NULL, wnd->front_buffer, NULL);
+
+  SDL_UpdateWindowSurface(wnd->window);
+}
+
+u32 colour_to_u32(colour_t colour) {
+  return ((u32)(colour.r) << 24) | ((u32)(colour.g) << 16) |
+         ((u32)(colour.b) << 8) | (u32)(colour.a);
+}
+
+u32 index_from_coordinates(window_t *wnd, u32 x, u32 y) {
+  return y * wnd->width + x;
+}
+
+i32 denormalise(f32 value, u32 max) {
+  if (max == 0 || value < NORMALISED_MIN || value >= NORMALISED_MAX) {
+    return -1;
+  }
+
+  return (i32)(((value - NORMALISED_MIN) * max) /
+               (NORMALISED_MAX - NORMALISED_MIN));
+}
+
+void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour) {
+  u32 index = index_from_coordinates(wnd, x, y);
+  u32 c = colour_to_u32(colour);
+
+  u32 *pixels = (u32 *)(wnd->back_buffer->pixels);
+
+  pixels[index] = c;
+}