| 1 | ; Project name : Assembly Library
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| 2 | ; Description : Functions for managing display page.
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| 3 |
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| 4 | ; Section containing code
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| 5 | SECTION .text
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| 6 |
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| 7 | ;--------------------------------------------------------------------
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| 8 | ; DisplayPage_SetFromAL
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| 9 | ; Parameters:
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| 10 | ; AL: New display page
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| 11 | ; DS: BDA segment (zero)
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| 12 | ; Returns:
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| 13 | ; Nothing
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| 14 | ; Corrupts registers:
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| 15 | ; AX, DX
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| 16 | ;--------------------------------------------------------------------
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| 17 | ALIGN JUMP_ALIGN
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| 18 | DisplayPage_SetFromAL:
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| 19 | xor ah, ah
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| 20 | mul WORD [VIDEO_BDA.wBytesPerPage] ; AX = Offset to page
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| 21 | mov [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition], ax
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| 22 | ret
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| 23 |
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| 24 |
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| 25 | ;--------------------------------------------------------------------
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| 26 | ; DisplayPage_GetColumnsToALandRowsToAH
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| 27 | ; Parameters:
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| 28 | ; DS: BDA segment (zero)
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| 29 | ; Returns:
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| 30 | ; AL: Number of columns in selected text mode
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| 31 | ; AH: Number of rows in selected text mode
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| 32 | ; Corrupts registers:
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| 33 | ; Nothing
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| 34 | ;--------------------------------------------------------------------
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| 35 | ALIGN JUMP_ALIGN
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| 36 | DisplayPage_GetColumnsToALandRowsToAH:
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| 37 | mov al, [VIDEO_BDA.wColumns] ; 40 or 80
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| 38 | mov ah, 25 ; Always 25 rows on standard text modes
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| 39 | ret
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| 40 |
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| 41 |
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| 42 | ;--------------------------------------------------------------------
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| 43 | ; DisplayPage_SynchronizeToHardware
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| 44 | ; Parameters:
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| 45 | ; DS: BDA segment (zero)
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| 46 | ; Returns:
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| 47 | ; Nothing
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| 48 | ; Corrupts registers:
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| 49 | ; AX, DX
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| 50 | ;--------------------------------------------------------------------
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| 51 | ALIGN JUMP_ALIGN
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| 52 | DisplayPage_SynchronizeToHardware:
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| 53 | xor dx, dx
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| 54 | mov ax, [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition]
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| 55 | div WORD [VIDEO_BDA.wBytesPerPage] ; AX = Page
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| 56 |
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| 57 | cmp al, [VIDEO_BDA.bActivePage]
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| 58 | je SHORT .Return ; Same page, no need to synchronize
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| 59 | mov ah, SELECT_ACTIVE_DISPLAY_PAGE
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| 60 | int BIOS_VIDEO_INTERRUPT_10h
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| 61 | .Return:
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| 62 | ret
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