How to set display start via VESA BIOS function 0x4F07

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CandyMan

Joined: 04 Sep 2009
Posts: 414
Location: film "CandyMan" directed through Bernard Rose OR Candy Shop

CandyMan 20 Aug 2019, 19:44

Code:

SetDisplayStart1:
        MOV     ECX,[X]
        MOV     EDX,[Y]
        MOV     EAX,$4F07
        XOR     EBX,EBX
        INT     $10
        RET

SetDisplayStart2:
        MOV     ECX,[X]
        MOV     EDX,[Y]

        MOV     EAX,$4F07
        XOR     EBX,EBX

        IMUL    EDX,[BytesPerLine]
        IMUL    ECX,[BytesPerPixel]
        ADD     EDX,ECX
        SHR     EDX,2
        
        MOVZX   ECX,DX
        SHR     EDX,16
        
        CALL    [PtrSetDispStart] ;PM32 function 0x4F07
        RET

The first procedure works in all modes. However, the second procedure does not work in 8-bit mode (blinking). Should something be improved?

20 Aug 2019, 19:44

bitRAKE

Joined: 21 Jul 2003
Posts: 4075
Location: vpcmpistri

bitRAKE 20 Aug 2019, 21:51

I'm sorry, don't understand this calculation:

Code:

        IMUL    EDX,BytesPerLine
        IMUL    ECX,BytesPerPixel
        ADD     EDX,ECX
        SHR     EDX,2

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20 Aug 2019, 21:51

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