root/core/font.inc

;; -----------------------------------------------------------------------
;;
;;   Copyright 1994-2008 H. Peter Anvin - All Rights Reserved
;;
;;   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, Inc., 53 Temple Place Ste 330,
;;   Boston MA 02111-1307, USA; either version 2 of the License, or
;;   (at your option) any later version; incorporated herein by reference.
;;
;; -----------------------------------------------------------------------

;;
;; font.inc
;;
;; VGA font handling code
;;

                section .text16

;
; loadfont:     Load a .psf font file and install it onto the VGA console
;               (if we're not on a VGA screen then ignore.)
;               The font is on top of the getc stack.
;
loadfont.err:   jmp close                       ; Tailcall the close routine

loadfont:
                mov di,trackbuf
                mov cx,4
                call readc                      ; Read header
                jc .err

                mov ax,[trackbuf]               ; Magic number
                cmp ax,0436h
                jne .err

                mov al,[trackbuf+2]             ; File mode
                cmp al,5                        ; Font modes 0-5 supported
                ja .err

                xor bx,bx
                mov bh,[trackbuf+3]             ; Height of font
                cmp bh,2                        ; VGA minimum
                jb .err
                cmp bh,32                       ; VGA maximum
                ja .err

                ; Load the actual font
                mov di,trackbuf
                mov cx,bx                       ; Bytes = font height * 256
                call readc
                jc .err

                call close

                ; Copy to font buffer
                mov si,trackbuf                 ; Start of font data
                mov [VGAFontSize],bh
                push es
                mov cx,aux_seg
                mov es,cx
                mov di,aux.fontbuf
                mov cx,bx
                shr cx,2
                rep movsd
                pop es

                mov [UserFont], byte 1          ; Set font flag

;
; use_font:
;       This routine activates whatever font happens to be in the
;       vgafontbuf, and updates the adjust_screen data.
;       Must be called with CS = DS
;
use_font:
                test byte [UsingVGA], ~03h      ; Nonstandard mode?
                jz .modeok
                call vgaclearmode

.modeok:
                test [UserFont], byte 1         ; Are we using a user-specified font?
                jz adjust_screen                ; If not, just do the normal stuff

                push es
                mov bp,aux_seg
                mov es,bp

                mov bp,aux.fontbuf              ; ES:BP -> font
                mov bh,[VGAFontSize]
                xor bl,bl                       ; Needed by both INT 10h calls

                test byte [UsingVGA], 01h       ; Are we in graphics mode?
                jz .text

.graphics:
                xor cx,cx
                mov cl,bh                       ; CX = bytes/character
                mov ax,[GXPixRows]
                div cl                          ; Compute char rows per screen
                mov dl,al
                dec ax
                mov [VidRows],al
                mov ax,1121h                    ; Set user character table
                int 10h
                mov ax,[GXPixCols]
                shr ax,3                        ; 8 pixels/character
                dec ax
                mov [VidCols],al
                pop es
                ret                             ; No need to call adjust_screen

.text:
                mov cx,256
                xor dx,dx
                mov ax,1110h
                int 10h                         ; Load into VGA RAM
                pop es

                xor bl,bl
                mov ax,1103h                    ; Select page 0
                int 10h

;
; adjust_screen: Set the internal variables associated with the screen size.
;               This is a subroutine in case we're loading a custom font.
;
adjust_screen:
                pusha
                mov al,[BIOS_vidrows]
                and al,al
                jnz vidrows_ok
                mov al,24                       ; No vidrows in BIOS, assume 25
                                                ; (Remember: vidrows == rows-1)
vidrows_ok:     mov [VidRows],al
                mov ah,0fh
                int 10h                         ; Read video state
                dec ah                          ; Store count-1 (same as rows)
                mov [VidCols],ah
                popa
                ret

                section .data16
                alignz 2
VGAFontSize     dw 16                   ; Defaults to 16 byte font
UserFont        db 0                    ; Using a user-specified font

                section .bss16
                alignb 4
GXPixCols       resw 1                  ; Graphics mode pixel columns
GXPixRows       resw 1                  ; Graphics mode pixel rows