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I think, the GDI api LineDDA don't works correct. Look at this. The black line was made with MoveToEx/LineTo and the blue line was made with LineDDA and callback procedure:



Here is my code (in XProfan with inlineassembler XPIA):

{$iq}

Declare x&,y&,text$

Cls

If 0
  AsmInclude
    LineDDAProc proc ;#################################################################################################

      mov eax,
      mov ebx,
      mov ecx,

      invoke SetPixel,ecx,eax,ebx,0FF0000h

      mov eax,1
      ret 12
    LineDDAProc endp
  AsmEnd
EndIf

AsmStart LinePoints(%HDC)

  invoke MoveToEx,para1,40,40,0
  invoke LineTo,para1,400,150
  
  invoke LineDDA,40,40,400,150,addr LineDDAProc,para1 

AsmEnd

WaitInput
End

Does someone know what's goeing wrong?

Best regards,
Nordwind64

Thank you f0dder!

You're right. Silly bug... This one works correct:

    LineDDAProc proc ;#################################################################################################

      push ebp
      mov  ebp,esp

      push eax
      push ebx
      push ecx
      
      mov eax,
      mov ebx,
      mov ecx,
      invoke SetPixel,ecx,eax,ebx,0FF0000h

      pop ecx
      pop ebx
      pop eax
      
      pop ebp
      ret 12
    LineDDAProc endp

Hi.



...only an examplecode  8)

Regards, Nordwind