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DIBSection Help
Post by Ric on Nov 1st, 2015, 7:50pm

I have typed the code in the following link http://bb4w.wikispaces.com/Direct+screen+memory+access
Only to get the error "couldn't create DIBSection". I don't really understand the code but the error only occurs if hbitmap% =0 so can I set the value to the last bit in the DIBSection or is it causing an error because I only have the trial version? Can anyone help?
Re: DIBSection Help
Post by DDRM on Nov 3rd, 2015, 07:32am

Hi Ric,

hbitmap% is returned by the call: you can't set it yourself. If it is 0 it means that the system failed to create the DIBSection. Either one of your parameters wasn't what was required, or potentially memory wasn't available.

Best wishes,

D
Re: DIBSection Help
Post by Ric on Nov 5th, 2015, 2:11pm

Hi DDRM
I have now corrected the code (guilty of failing to transpose properly!!!!), as you are probably aware by now I am trying to create ASM routines to produce he graphics I require. And thus, is it possible to access bits% directly from assembly?
Regards Ric
Re: DIBSection Help
Post by David Williams on Nov 5th, 2015, 2:30pm

on Nov 5th, 2015, 2:11pm, Ric wrote:
Hi DDRM
I have now corrected the code (guilty of failing to transpose properly!!!!), as you are probably aware by now I am trying to create ASM routines to produce he graphics I require. And thus, is it possible to access bits% directly from assembly?
Regards Ric


Yes, for example:

Code:
mov eax, bits%

or

Code:
mov eax, [^bits%]


The former assumes that bits% is (and remains) constant; the latter allows for differing/variable values of bits% from one call of the machine code routine to the next.
Re: DIBSection Help
Post by Ric on Nov 5th, 2015, 3:11pm

Thanks David,
This instruction obviously puts the value in eax into bits%, but the manual I am looking at would suggest that the instruction should put the value in bits% into eax. I am confused. can you point me in the right direction for a user guide for the assembly language.
Regards Ric
Re: DIBSection Help
Post by Ric on Nov 5th, 2015, 3:27pm

David,

Thought about the instruction you posted a bit more, bits% is an array, does this matter?

the operation I would like to perform in to make bits%?(<variable>wink=<variable> simple in basic but when I try to perform this in asm I get a syntax or size error.

MOV bit%, ax

fails I know now because the variable is not allowed to be the destination operand, this is what I can not solve.

Do I need to transfer the memory location of bits% to a register and MOV to that location? I have tried this and it crashes bb4w!

HELP

Ric
Re: DIBSection Help
Post by David Williams on Nov 5th, 2015, 4:17pm

Ric, I've written the following bit of example code in a huge hurry (I'm about to go out). Perhaps you'll find it of some use?

Just copy and paste it into the BB4W IDE, and run it. It just displays a coloured pattern.

Code:
      ON ERROR PROCError(REPORT$ + " at line " + STR$ERL)

      ScrW% = 640
      ScrH% = 512
      PROCFixWndSz
      VDU 23,22,ScrW%;ScrH%;8,16,16,0

      bits% = FNCreateDIBSection

      DIM code% 127

      FOR I% = 0 TO 2 STEP 2
        P% = code%
        [OPT I%
  
        mov eax, [^bits%]    ; base address of DIBSection
        mov ecx, ScrW%*ScrH% ; no. of pixels to write
        mov edx, &12345678   ; colour
  
        .lp
        mov [eax], edx       ; write pixel to DIBSection
        add eax, 4           ; inc. addr by 4 bytes
        sub edx, &01020305
        dec ecx              ; dec loop counter
        jg lp                ; loop if > 0
  
        ret
  
        ]
      NEXT I%

      CALL code%

      SYS "InvalidateRect", @hwnd%, 0, 0
      *REFRESH
      END

      DEFFNCreateDIBSection
      LOCAL A%,B%,H%,O%
      DIM B% 19:!B%=44:B%!4=@vdu%!208:B%!8=@vdu%!212:B%!12=&200001
      SYS"CreateDIBSection",@memhdc%,B%,0,^A%,0,0TOH%
      IF H%=0 PROCError("Create DIBSection failed")
      SYS"SelectObject",@memhdc%,H%TOO%
      SYS"DeleteObject",O%
      CLS
      =A%

      DEF PROCFixWndSz
      LOCAL W%
      SYS"GetWindowLong",@hwnd%,-16 TO W%
      SYS"SetWindowLong",@hwnd%,-16,W% ANDNOT&40000 ANDNOT&10000
      ENDPROC

      DEF PROCError(s$)
      OSCLI "REFRESH ON"
      CLS : ON : VDU 7
      PRINT '" " + s$;
      REPEAT UNTIL INKEY(1)=0
      ENDPROC




David.
Re: DIBSection Help
Post by David Williams on Nov 6th, 2015, 07:44am

Here's a slightly neater, more efficient version of the code I put up yesterday. The program does a similar thing - just displays a colourful pattern. Copy, paste, and run:

Code:
      ON ERROR PROCError(REPORT$ + " at line " + STR$ERL)

      ScrW% = 512
      ScrH% = 512
      PROCFixWndSz
      VDU 23,22,ScrW%;ScrH%;8,16,16,0

      REM Create 32bpp (ARGB &AARRGGBB) DIBSection:
      bits% = FNCreateDIBSection

      DIM code% 127

      FOR I% = 0 TO 2 STEP 2
        P% = code%
        [OPT I%
  
        mov eax, [^bits%]    ; base address of DIBSection colour bits (pixels)
        mov ecx, ScrW%*ScrH% ; no. of pixels to write (4 bytes per pixel)
        mov edx, &00654321   ; initial (&AARRGGBB) colour
  
        .lp
        mov [eax + 4*ecx -4], edx ; write pixel to DIBSection
        sub edx, &00010101        ; update/modify colour
        loopnz lp                 ; ECX is automatically decremented & checked
  
        ret
  
        ]
      NEXT I%

      CALL code%

      SYS "InvalidateRect", @hwnd%, 0, 0
      *REFRESH
      END

      DEFFNCreateDIBSection
      LOCAL A%,B%,H%,O%
      DIM B% 19:!B%=44:B%!4=@vdu%!208:B%!8=@vdu%!212:B%!12=&200001
      SYS"CreateDIBSection",@memhdc%,B%,0,^A%,0,0TOH%
      IF H%=0 PROCError("Create DIBSection failed")
      SYS"SelectObject",@memhdc%,H%TOO%
      SYS"DeleteObject",O%
      CLS
      =A%

      DEF PROCFixWndSz
      LOCAL W%
      SYS"GetWindowLong",@hwnd%,-16 TO W%
      SYS"SetWindowLong",@hwnd%,-16,W% ANDNOT&40000 ANDNOT&10000
      ENDPROC

      DEF PROCError(s$)
      OSCLI "REFRESH ON"
      CLS : ON : VDU 7
      PRINT '" " + s$;
      REPEAT UNTIL INKEY(1)=0
      ENDPROC
Re: DIBSection Help
Post by Ric on Nov 6th, 2015, 08:42am

Thanks once again David, hope your night out was OK. I went on a step learning curve last night, the code you sent to create the DIBSection was different to the one I was using which caused me a headache at first but once I realised it needed to be 32bpp suddenly the penny dropped. Another penny dropped in understanding that ie. eax was a 32bit register and that effects 4 double byte locations. So &00FFFFFF is white and not &FF &FF &FF which was the way I was doing it in basic. In the early nineties I did a degree in computer engineering would you believe, I don't recall any of this being on it , maybe I've just forgotten! Age! I am now set to create the sprite routines, so many thanks again to yourself and DDRM for your input, (I may need it againwink ).


PS. Is there a sensible manual I can download?
Re: DIBSection Help
Post by ady on Nov 6th, 2015, 09:01am

PS. Is there a sensible manual I can download?

That's where ketman comes in, you can SEE what is happening instead of imagining or guessing, especially when it gets confusing
http://www.addogodfrey.clara.net/learn-32bit-X86-assembly-language.html
Re: DIBSection Help
Post by Ric on Nov 19th, 2015, 10:34am

Thanks Ady,
I have tried to download Ketman Maximaster, but it will not run because of issues about 64 bit machine, have you come across this before and is there a solution?

Regards Ric
Re: DIBSection Help
Post by ady on Nov 20th, 2015, 10:19am

It's quite a sophisticated program and unique as far as I am aware
I would reckon that you will need a 32 bit system to run it

XP32 is fine (alt-ENTER) lets you cycle to the full screen