Implement shaders (#1)

Reviewed-on: #1

	* Start implementing shaders and move vector code to dedicated files
	* Extract shader into its own header
	* Ensure pixel coordinates are within bounds
	* Refactor shader code and implement fragment shaders
	* Create shaders
	* Reorganise code
Co-authored-by: Abdelrahman <said.abdelrahman89@gmail.com>
Co-committed-by: Abdelrahman <said.abdelrahman89@gmail.com>

src/img/img.c

@@ -0,0 +1,93 @@
+#include "img.h"
+#include "aliases.h"
+#include "mem_arena.h"
+#include "pam.h"
+#include "utils.h"
+#include <stdbool.h>
+#include <stddef.h>
+#include <string.h>
+
+internal i64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y, u64 base_size);
+
+bool _init_buffer(Arena *arena, Buffer *buffer, u64 base_size) {
+  if (!arena || !buffer || buffer->width == 0 || buffer->height == 0) {
+    return false;
+  }
+
+  u64 size = buffer->width * buffer->height * base_size;
+  buffer->buf = wapp_mem_arena_alloc(arena, size);
+
+  return buffer->buf != NULL;
+}
+
+u8 *_get_pixel(Buffer *buffer, u64 x, u64 y, u64 base_size) {
+  i64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  if (idx == -1) {
+    idx = 0;
+  }
+
+  return ((u8 *)(buffer->buf)) + idx;
+}
+
+void _set_pixel(Buffer *buffer, u64 x, u64 y, void *value, u64 base_size) {
+  i64 idx = calculate_pixel_index(buffer, x, y, base_size);
+  if (idx == -1) {
+    return;
+  }
+
+  memcpy(((u8 *)(buffer->buf)) + idx, value, base_size);
+  return;
+}
+
+void _clear_buffer(Buffer *buffer, void *value, u64 base_size) {
+  for (u64 y = 0; y < buffer->height; ++y) {
+    for (u64 x = 0; x < buffer->width; ++x) {
+      _set_pixel(buffer, x, y, value, base_size);
+    }
+  }
+}
+
+void draw_line(Image *img, u64 x0, u64 y0, u64 x1, u64 y1, Colour colour) {
+  u64 dx = absolute((i64)x1 - (i64)x0);
+  u64 dy = absolute((i64)y1 - (i64)y0);
+  f32 t = 0.0f;
+  i64 x = 0;
+  i64 y = 0;
+
+  if (dx > dy) {
+    if (x0 > x1) {
+      swap(u64, x0, x1);
+      swap(u64, y0, y1);
+    }
+
+    for (u64 x = x0; x < x1; ++x) {
+      t = (f32)(x - x0) / (f32)(x1 - x0);
+      y = (i64)y0 + ((i64)y1 - (i64)y0) * t;
+      set_pixel(img, x, y, &colour);
+    }
+  } else {
+    if (y0 > y1) {
+      swap(u64, x0, x1);
+      swap(u64, y0, y1);
+    }
+
+    for (u64 y = y0; y < y1; ++y) {
+      t = (f32)(y - y0) / (f32)(y1 - y0);
+      x = (i64)x0 + ((i64)x1 - (i64)x0) * t;
+      set_pixel(img, x, y, &colour);
+    }
+  }
+}
+
+void save_image(const Image *img, const char *filename) {
+  write_p7_image(img->width, img->height, (u8 *)(img->buf), filename);
+}
+
+internal i64 calculate_pixel_index(Buffer *buffer, u64 x, u64 y,
+                                   u64 base_size) {
+  if (x < 0 || y < 0 || x >= buffer->width || y >= buffer->height) {
+    return -1;
+  }
+
+  return (y * buffer->width + x) * base_size;
+}

src/img/img.h

@@ -0,0 +1,43 @@
+#ifndef IMG_H
+#define IMG_H
+
+#include "aliases.h"
+#include "mem_arena.h"
+#include <stdbool.h>
+
+#define BUF_TYPE(TYPE, NAME)                                                   \
+  typedef struct NAME {                                                        \
+    u64 width;                                                                 \
+    u64 height;                                                                \
+    TYPE *buf;                                                                 \
+  } NAME
+
+typedef struct colour Colour;
+struct colour {
+  u8 r;
+  u8 g;
+  u8 b;
+  u8 a;
+};
+
+BUF_TYPE(void, Buffer);
+BUF_TYPE(Colour, Image);
+BUF_TYPE(f32, Depth);
+
+#define init_buffer(ARENA, BUF)                                                \
+  _init_buffer(ARENA, (Buffer *)BUF, sizeof(*((BUF)->buf)))
+#define get_pixel(TYPE, BUF, X, Y)                                             \
+  (*((TYPE *)(_get_pixel((Buffer *)BUF, X, Y, sizeof(*((BUF)->buf))))))
+#define set_pixel(BUF, X, Y, VAL_PTR)                                          \
+  _set_pixel((Buffer *)BUF, X, Y, VAL_PTR, sizeof(*((BUF)->buf)))
+#define clear_buffer(BUF, VAL_PTR)                                             \
+  _clear_buffer((Buffer *)BUF, VAL_PTR, sizeof(*((BUF)->buf)))
+
+bool _init_buffer(Arena *arena, Buffer *buffer, u64 base_size);
+u8 *_get_pixel(Buffer *buffer, u64 x, u64 y, u64 base_size);
+void _set_pixel(Buffer *buffer, u64 x, u64 y, void *value, u64 base_size);
+void _clear_buffer(Buffer *buffer, void *value, u64 base_size);
+void draw_line(Image *img, u64 x0, u64 y0, u64 x1, u64 y1, Colour colour);
+void save_image(const Image *img, const char *filename);
+
+#endif // IMG_H