source: xtideuniversalbios/trunk/Assembly_Library/Src/Display/DisplayPage.asm

; Project name  :   Assembly Library
; Description   :   Functions for managing display page.

;
; XTIDE Universal BIOS and Associated Tools
; Copyright (C) 2009-2010 by Tomi Tilli, 2011-2013 by XTIDE Universal BIOS Team.
;
; This program is free software; you can redistribute it and/or modify
; it under the terms of the GNU General Public License as published by
; the Free Software Foundation; either version 2 of the License, or
; (at your option) any later version.
;
; This program is distributed in the hope that it will be useful,
; but WITHOUT ANY WARRANTY; without even the implied warranty of
; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
; GNU General Public License for more details.
; Visit http://www.gnu.org/licenses/old-licenses/gpl-2.0.html
;

; Section containing code
SECTION .text

;--------------------------------------------------------------------
; DisplayPage_SetFromAL
;   Parameters:
;       AL:     New display page
;       DS:     BDA segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
%ifndef EXCLUDE_FROM_XUB OR EXCLUDE_FROM_XTIDECFG OR EXCLUDE_FROM_BIOSDRVS
ALIGN DISPLAY_JUMP_ALIGN
DisplayPage_SetFromAL:
    xor     ah, ah
    mul     WORD [VIDEO_BDA.wBytesPerPage]      ; AX = Offset to page
    mov     [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition], ax
    ret
%endif


%ifdef EXCLUDE_FROM_XUB
    %define EXCLUDE
    %ifdef MODULE_HOTKEYS OR MODULE_BOOT_MENU
        %undef EXCLUDE
    %endif
%endif

%ifndef EXCLUDE OR EXCLUDE_FROM_BIOSDRVS
;--------------------------------------------------------------------
; DisplayPage_GetColumnsToALandRowsToAH
;   Parameters:
;       DS:     BDA segment (zero)
;   Returns:
;       AL:     Number of columns in selected text mode
;       AH:     Number of rows in selected text mode
;   Corrupts registers:
;       Nothing
;--------------------------------------------------------------------
ALIGN DISPLAY_JUMP_ALIGN
DisplayPage_GetColumnsToALandRowsToAH:
    mov     al, [VIDEO_BDA.wColumns]        ; 40 or 80
    mov     ah, 25                          ; Always 25 rows on standard text modes
    ret
%endif
%undef EXCLUDE

;--------------------------------------------------------------------
; DisplayPage_SynchronizeToHardware
;   Parameters:
;       DS:     BDA segment (zero)
;   Returns:
;       Nothing
;   Corrupts registers:
;       AX, DX
;--------------------------------------------------------------------
ALIGN DISPLAY_JUMP_ALIGN
DisplayPage_SynchronizeToHardware:
    xor     dx, dx
    mov     ax, [VIDEO_BDA.displayContext+DISPLAY_CONTEXT.fpCursorPosition]
    div     WORD [VIDEO_BDA.wBytesPerPage]  ; AX = Page

    cmp     al, [VIDEO_BDA.bActivePage]
    je      SHORT .Return                   ; Same page, no need to synchronize
    mov     ah, SELECT_ACTIVE_DISPLAY_PAGE
    int     BIOS_VIDEO_INTERRUPT_10h
.Return:
    ret