Update examples/sdlex.nim

Updated sdlex.nim to show the basics of an SDL app (event loop, input)

examples/sdlex.nim

@@ -1,26 +1,52 @@
 # Test the SDL interface:
 
 import
-  SDL
+  sdl, sdl_image, colors
 
 var
   screen, greeting: PSurface
   r: TRect
+  event: TEvent
+  bgColor = colChocolate.int32
 
-if Init(INIT_VIDEO) == 0:
-  screen = SetVideoMode(640, 480, 16, SWSURFACE or ANYFORMAT)
-  if screen == nil:
-    write(stdout, "screen is nil!\n")
-  else:
-    greeting = LoadBmp("backgrnd.bmp")
-    if greeting == nil:
-      write(stdout, "greeting is nil!")
-    r.x = 0'i16
-    r.y = 0'i16
-    discard blitSurface(greeting, nil, screen, addr(r))
-    discard flip(screen)
-    Delay(3000)
+if init(INIT_VIDEO) != 0:
+  quit "SDL failed to initialize!"
+
+screen = SetVideoMode(640, 480, 16, SWSURFACE or ANYFORMAT)
+if screen.isNil:
+  quit($sdl.getError())
+
+greeting = IMG_load("tux.png")
+if greeting.isNil:
+  echo "Failed to load tux.png"
 else:
-  write(stdout, "SDL_Init failed!\n")
+  ## convert the image to alpha and free the old one
+  var s = greeting.displayFormatAlpha()
+  swap(greeting, s)
+  s.freeSurface()
 
+r.x = 0
+r.y = 0
+
+block game_loop:
+  while true:
+    
+    while pollEvent(addr event) > 0:
+      case event.kind
+      of QUITEV:
+        break game_loop
+      of KEYDOWN:
+        if EvKeyboard(addr event).keysym.sym == K_ESCAPE:
+          break game_loop
+      else:
+        discard
+    
+    discard fillRect(screen, nil, bgColor) 
+    discard blitSurface(greeting, nil, screen, addr r)
+    discard flip(screen)
+
+greeting.freeSurface()
+screen.freeSurface()
 sdl.Quit()
+
+## fowl wuz here 10/2012