Please help me with Interface Stuff

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Suco-X

Hi.
At moment i test my first Interface with the SDL Lib. But i had some unexplainable(for me) problems with Correctly Structur Import.
Let´s begin :
The SDL_Surface Structure http://www.libsdl.org/cgi/docwiki.cgi/SDL_5fSurface

My Test Code

Import "-lsdl.dll"

extern "C"

type SDL_Surface

  field flags:int                           
  field format:byte ptr            
  field w:int,h:int                              
  field pitch:short                           
  field pixels:byte ptr                          
  field clip_rect:byte ptr                    
  field refcount:int  
end type


Function SDL_Init(Flags:Int)
Function SDL_SetVideoMode:SDL_Surface(Width:Int, Height:Int, Depth:Int, Flags:Int)
Function SDL_Flip(Screen:SDL_Surface)
Function SDL_FillRect(dst:SDL_Surface, dstrect:byte ptr, color:Int)
end extern


Const SDL_INIT_VIDEO              = $00000020
Const SDL_HWSURFACE               = $00000001
Const SDL_DOUBLEBUF               = $40000000
Const SDL_FULLSCREEN              = $80000000



if SDL_Init(SDL_INIT_VIDEO)=-1
	end
endif

local ScreenSurface:SDL_Surface = SDL_SetVideoMode(800,600,32,SDL_HWSURFACE|SDL_DOUBLEBUF)
print ScreenSurface.w
print ScreenSurface.h 

Repeat
SDL_FillRect(ScreenSurface,null,$FFFFFF)
SDL_Flip(ScreenSurface)
FlushMem()
Until KeyHit(KEY_ESCAPE)

The Problem :
This Code works without Errors.
But the ScreenSurface Data are wrong. Prints :
w: 600
h: 3200

I Think the Data is in disorder. But i dont know what i can do. Please help me a bit.
Mfg Suco