Nim 和 SDL2 的 Rect 问题

Question

我有以下 Nim+official libsdl2包装器代码

import sdl2

discard sdl2.init(INIT_EVERYTHING)

let
  window = createWindow("Tic-Tac-Toe", SDL_WINDOWPOS_CENTERED, SDL_WINDOWPOS_CENTERED, 600, 390, SDL_WINDOW_SHOWN)
  renderer = createRenderer(window, -1, Renderer_Accelerated or Renderer_PresentVsync or Renderer_TargetTexture)

proc loadImage(file: string): TexturePtr =
  let loadedImage = loadBMP(file)
  let texture = createTextureFromSurface(renderer, loadedImage)
  freeSurface(loadedImage)
  return texture

proc applySurface(x: cint, y: cint, tex: TexturePtr, rend: RendererPtr) =
  var pos: Rect
  pos.x = x
  pos.y = y
  queryTexture(tex, nil, nil, pos.w, pos.h)
  copy(rend, tex, nil, pos)

let
  background = loadImage("resources/bg.bmp")

clear(renderer)
applySurface(0, 0, background, renderer)
present(renderer)

var
  evt = sdl2.defaultEvent
  runGame = true

while runGame:
  while pollEvent(evt):
    if evt.kind == QuitEvent:
      runGame = false
      break

destroy window

并且在编译过程中出现错误：

source.nim(19, 15) Error: type mismatch: got (TexturePtr, nil, nil, cint, cint)
but expected one of: 
sdl2.queryTexture(texture: TexturePtr, format: ptr uint32, access: ptr cint, w: ptr cint, h: ptr cint)

第 20 行相同：

source.nim(20, 7) Error: type mismatch: got (RendererPtr, TexturePtr, nil, Rect)
but expected one of: 
system.copy(s: string, first: int)
system.copy(s: string, first: int, last: int)
sdl2.copy(renderer: RendererPtr, texture: TexturePtr, srcrect: ptr Rect, dstrect: ptr Rect)

如果在copy()中用nil替换pos并注释queryTexture()，一切都会好起来的。请帮我解决这个问题。

Answer 1

您的问题是 procs 需要ptr相应的数据类型，而不是数据本身。例如 aptr cint是必需的，但您正在传递一个普通的cint. 什么，你需要做的是采取addr的cint获得ptr cint。例如：

var w = pos.w
var h = pos.h
queryTexture(tex, nil, nil, w.addr, h.addr)

请注意，为了“获取地址”，您需要一个该var类型的变量（有关详细信息，请参阅此问题）。既然pos是var，pos.w.addr也pos.h.addr应该工作。同样你必须要pos.addr为最后一个参数copy。