cg-from-scratch/src/window/window.c

#include "window/window.h"
#include "aliases.h"
#include "math/math_utils.h"
#include "vector/vec.h"
#include <SDL2/SDL.h>
#include <SDL2/SDL_error.h>
#include <SDL2/SDL_pixels.h>
#include <SDL2/SDL_surface.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>

u32 index_from_coordinates(window_t *wnd, u32 x, u32 y);
i32 denormalise(i32 value, u32 max, u32 abs_half);
vec2i_t denormalised_coords(const window_t *wnd, i32 x, i32 y);
void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour);

bool init_window(window_t *wnd, u32 width, u32 height, const char *title) {
  if (SDL_Init(SDL_INIT_EVERYTHING) != 0) {
    printf("Failed to initialise SDL: %s\n", SDL_GetError());

    return false;
  }

  if (width % 2 != 0) {
    ++width;
  }

  if (height % 2 != 0) {
    ++height;
  }

  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->half_width = width / 2;
  wnd->half_height = height / 2;
  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 *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] = colour.colour;
  }

  SDL_UnlockSurface(wnd->back_buffer);
}

void set_pixel(window_t *wnd, i32 x, i32 y, colour_t colour) {
  vec2i_t coords = denormalised_coords(wnd, x, y);

  if (coords.x < 0 || coords.y < 0) {
    return;
  }

  SDL_LockSurface(wnd->back_buffer);

  set_screen_pixel(wnd, (u32)(coords.x), (u32)(coords.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 index_from_coordinates(window_t *wnd, u32 x, u32 y) {
  return y * wnd->width + x;
}

i32 denormalise(i32 value, u32 max, u32 abs_half) {
  if (max == 0) {
    return -1;
  }

  i32 normalised_min = -abs_half;
  i32 normalised_max = abs_half;

  i32 denormalised = (i32)(((value - normalised_min) * max) /
                           (normalised_max - normalised_min));

  if (denormalised < 0 || denormalised >= max) {
    return -1;
  }

  return denormalised;
}

vec2i_t denormalised_coords(const window_t *wnd, i32 x, i32 y) {
  i32 screen_x = denormalise(x, wnd->width, wnd->half_width);
  i32 screen_y = denormalise(-y, wnd->height, wnd->half_height);

  return (vec2i_t){.x = screen_x, .y = screen_y};
}

void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour) {
  u32 index = index_from_coordinates(wnd, x, y);
  u32 *pixels = (u32 *)(wnd->back_buffer->pixels);

  pixels[index] = colour.colour;
}

vec3f_t window_to_viewport(window_t *wnd, i32 x, i32 y, vec3f_t viewport) {
  return (vec3f_t){
      .x = x * viewport.x / wnd->width,
      .y = y * viewport.y / wnd->height,
      .z = viewport.z,
  };
}

colour_t colour_add_colour(colour_t a, colour_t b) {
  f32 alpha = clamp((f32)(a.rgba.a + b.rgba.a), 0.0f, (f32)UINT8_MAX);

  return (colour_t){.rgba.r = a.rgba.r + b.rgba.r,
                    .rgba.g = a.rgba.g + b.rgba.g,
                    .rgba.b = a.rgba.b + b.rgba.b,
                    .rgba.a = (u8)alpha};
}

colour_t colour_mul(colour_t colour, f32 scalar) {
  f32 r = (f32)colour.rgba.r * scalar;
  r = clamp(r, 0.0f, (f32)UINT8_MAX);
  f32 g = (f32)colour.rgba.g * scalar;
  g = clamp(g, 0.0f, (f32)UINT8_MAX);
  f32 b = (f32)colour.rgba.b * scalar;
  b = clamp(b, 0.0f, (f32)UINT8_MAX);

  return (colour_t){.rgba.r = (u8)r,
                    .rgba.g = (u8)g,
                    .rgba.b = (u8)b,
                    .rgba.a = colour.rgba.a};
}