Add function to convert from window coordinates to viewport

include/window/window.h

@@ -2,6 +2,7 @@
 #define WINDOW_H
 
 #include "c_cpp_aliases/aliases.h"
+#include "vector/vec.h"
 #include <SDL2/SDL_video.h>
 #include <stdbool.h>
 
@@ -30,4 +31,6 @@ void clear_window(window_t *wnd, colour_t colour);
 void set_pixel(window_t *wnd, i32 x, i32 y, colour_t colour);
 void swap_buffers(window_t *wnd);
 
+vec3f_t window_to_viewport(window_t *wnd, i32 x, i32 y, vec3f_t viewport);
+
 #endif // !WINDOW_H

src/window/window.c

@@ -1,5 +1,6 @@
 #include "window/window.h"
 #include "c_cpp_aliases/aliases.h"
+#include "vector/vec.h"
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_error.h>
 #include <SDL2/SDL_pixels.h>
@@ -10,6 +11,7 @@
 u32 colour_to_u32(colour_t colour);
 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) {
@@ -103,16 +105,15 @@ void clear_window(window_t *wnd, colour_t colour) {
 }
 
 void set_pixel(window_t *wnd, i32 x, i32 y, colour_t colour) {
-  i32 screen_x = denormalise(x, wnd->width, wnd->half_width);
-  i32 screen_y = denormalise(-y, wnd->height, wnd->half_height);
+  vec2i_t coords = denormalised_coords(wnd, x, y);
 
-  if (screen_x < 0 || screen_y < 0) {
+  if (coords.x < 0 || coords.y < 0) {
     return;
   }
 
   SDL_LockSurface(wnd->back_buffer);
 
-  set_screen_pixel(wnd, (u32)screen_x, (u32)screen_y, colour);
+  set_screen_pixel(wnd, (u32)(coords.x), (u32)(coords.y), colour);
 
   SDL_UnlockSurface(wnd->back_buffer);
 }
@@ -150,6 +151,13 @@ i32 denormalise(i32 value, u32 max, u32 abs_half) {
   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 c = colour_to_u32(colour);
@@ -158,3 +166,11 @@ void set_screen_pixel(window_t *wnd, u32 x, u32 y, colour_t colour) {
 
   pixels[index] = c;
 }
+
+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,
+  };
+}