Pixel perfect viewport with resolution scaling

viewport.odin

GAME_WIDTH  :: f32(320)
GAME_HEIGHT :: f32(180)

gfx_get_resolution_scaling :: proc(window_pixel_width, window_pixel_height: i32) -> int
{
  dpi_scale := sdl.GetWindowPixelDensity(G.WINDOW)

  width := f32(window_pixel_width) * dpi_scale
  height := f32(window_pixel_height) * dpi_scale

  window_aspect_ratio := width / height
  game_aspect_ratio := GAME_WIDTH / GAME_HEIGHT

  res := int(height / GAME_HEIGHT if game_aspect_ratio < window_aspect_ratio else width / GAME_WIDTH)

  return res if res > 1 else 1
}

gfx_get_pixel_perfect_viewport :: proc(window_pixel_width, window_pixel_height: i32, resolution_scale: int) -> sdl.GPUViewport
{
  dpi_scale := sdl.GetWindowPixelDensity(G.WINDOW)

  width := f32(window_pixel_width) * dpi_scale
  height := f32(window_pixel_height) * dpi_scale
  scale := f32(resolution_scale)

  platform_width := GAME_WIDTH * scale
  platform_height := GAME_HEIGHT * scale

  vp_x := (width - platform_width) / 2
  vp_y := (height - platform_height) / 2
  vp_w := platform_width
  vp_h := platform_height

  vp := sdl.GPUViewport {
    x = sdl.roundf(vp_x),
    y = sdl.roundf(vp_y),
    w = sdl.roundf(vp_w),
    h = sdl.roundf(vp_h),
  }

  return vp
}

resolution_scale := gfx_get_resolution_scaling(window_width, window_height)
viewport := gfx_get_pixel_perfect_viewport(window_width, window_height, resolution_scale)