Add tests for examples from Nim in Action.

tests/niminaction/Chapter8/sdl/sdl.nim

@@ -0,0 +1,34 @@
+when defined(Windows):
+  const libName* = "SDL2.dll"
+elif defined(Linux):
+  const libName* = "libSDL2.so"
+elif defined(MacOsX):
+  const libName* = "libSDL2.dylib"
+
+type
+  SdlWindow = object
+  SdlWindowPtr* = ptr SdlWindow
+  SdlRenderer = object
+  SdlRendererPtr* = ptr SdlRenderer
+
+const INIT_VIDEO* = 0x00000020
+
+{.push dynlib: libName.}
+proc init*(flags: uint32): cint {.importc: "SDL_Init".}
+
+proc createWindowAndRenderer*(width, height: cint, window_flags: cuint,
+    window: var SdlWindowPtr, renderer: var SdlRendererPtr): cint
+    {.importc: "SDL_CreateWindowAndRenderer".}
+
+proc pollEvent*(event: pointer): cint {.importc: "SDL_PollEvent".}
+
+proc setDrawColor*(renderer: SdlRendererPtr, r, g, b, a: uint8): cint
+    {.importc: "SDL_SetRenderDrawColor", discardable.}
+
+proc present*(renderer: SdlRendererPtr) {.importc: "SDL_RenderPresent".}
+
+proc clear*(renderer: SdlRendererPtr) {.importc: "SDL_RenderClear".}
+
+proc drawLines*(renderer: SdlRendererPtr, points: ptr tuple[x, y: cint],
+    count: cint): cint {.importc: "SDL_RenderDrawLines", discardable.}
+{.pop.}