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Creature wrote:Or you could use a bitmap version of the Bochs font instead and load that from disk (or through multiboot modules). But it's probably faster to do it through the BIOS (no disk loading involved, so no errors can occur following from that).

Gigasoft wrote:First of all, you're loading the font into video RAM while in graphics mode. What would that be good for? You're just overwriting certain columns on the screen. Then you set the block specifier, which does nothing in graphics mode. Then you enable color planes 0, 1 and 2 but not 3 (why?).

Then, when printing, you retrieve the current cursor position and size and do nothing with it before you try to print the string (with DS still pointing at the video ROM and with the controller set to the wrong addressing mode after trying to load the font).

You don't need to retrieve or set any fonts to print characters using the BIOS. You only need to retrieve the font if you intend to draw characters manually without using the BIOS.

chooseBootingMode db "Would you like to perform a verbose boot?", 0x000d, 0x000a, 0

main:
    xor ax, ax
    mov ds, ax

    call getFont
    call mode13h
    call clearScreen
	
    mov bp, chooseBootingMode
    call printString
	
    jmp $

getFont:
    mov ax, 0x1130
	mov bh, 0x0002
	int 0x0010
	
	push es
	pop ds
	mov si, bp
	
	push cs
	pop es
	mov di, fontBuffer
	
	mov cx, 256
	
	populateBuffer:
	    movsw
		movsw
		movsw
		movsw
		movsw
		movsw
		movsw
		movsw
	loop populateBuffer
	
	mov bp, fontBuffer
	xor dx, dx
	mov cx, 256
	mov bh, 16
	mov bl, 1
	mov ax, 0x1100
	int 0x0010
	
	mov bx, 0x0100
	mov cx, bx
	shl bh, 2
	or bl, bh
	mov ax, 0x1103
	int 0x0010
	ret
printString:
    mov ah, 0x000f
	int 0x0010
	
	mov ah, 0x0003
	int 0x0010
	
	mov cx, 44
	mov bl, 0x0007
	mov ax, 0x1301
	int 0x0010
	ret
fontBuffer:

Gigasoft wrote:Well, the essential problems I was trying to point out were:

- Using a text mode font upload service while in graphics mode. This causes screen corruption, since plane 2, where the text mode font resides while in text mode, now contains pixels. More importantly, the BIOS will set the card back to text mode addressing after uploading the font, so that further accesses to the display memory will affect the wrong memory locations.
- When you print the string, DS points to the wrong segment. It points to the ROM font's segment instead of your own segment.

Gigasoft wrote:Well, no. I'm not sure why you're trying to upload the font. That would only be useful in text mode. When changing to graphics mode, the font is erased because the memory is used for something else. The block specifier is also meaningless in graphics mode.

To change the font used to print text in graphics mode, you should use one of the functions 1120h through 1124h. This should be done after switching to graphics mode.

Gigasoft wrote:Well, almost. Function 1120h is for loading an 8x8 font, so it should be function 1121h (or function 1122h to use the ROM 8x14 font.)

And you should make sure you don't print beyond the right side of the screen with function 13h, because the text will continue on the next screen row instead of advancing by the correct number of rows (the character height).

chooseBootingMode db "Would you like to perform a verbose boot?", 0x000d, 0x000a, 0

main:
    xor ax, ax
    mov ds, ax

	call mode13h
	call getFont
    call clearScreen
	
	mov bp, chooseBootingMode
    call printString
	
    jmp $

getFont:
    mov ax, 0x1130
	xor bh, bh
	int 0x0010

	mov ax, 0x1120
	int 0x0010
	ret
printString:
    mov ah, 0x000f
	int 0x0010
	
	mov ah, 0x0003
	int 0x0010
	
	mov cx, 44
	mov bl, 0x0007
	mov ax, 0x1301
	int 0x0010
	ret

Gigasoft wrote:Your getFont function does nothing right now. It basically sets the font used for CGA mode to what it was before.

Does ES point to your segment when calling printString? Try setting DX to 0 before invoking function 13h, just to make sure that this isn't the problem.

And there is no visible cursor in graphics mode. The cursor is only displayed in text mode.

getFont:
    mov ax, 0x1130
	mov bh, 0x0002
	int 0x0010

	mov ax, 0x1121
	mov cx, 256
	xor bl, bl
	mov dl, 200
	int 0x0010
	ret

Gigasoft wrote:No, what I meant was xor dx,dx before this (to starting printing a column 0, row 0), not before the call to mode13h:
mov ax, 0x1301
int 0x0010
But now it at least prints something, so that wasn't the problem.

The garbage printed indicates that ES is set to the wrong value when calling printString.

The parameters to function 1121h are wrong. Bytes per character (CX) should be 14. DL should be 01, for 14 text rows (the maximum that will fit in 200 screen rows).

chooseBootingMode db "Would you like to perform a verbose boot?", 0x000d, 0x000a, 0

main:
    xor ax, ax
    mov ds, ax
	
	call mode13h
	call getFont
    call clearScreen
	
	mov bp, chooseBootingMode
    call printString
	
    jmp $

getFont:
    mov ax, 0x1130
	mov bh, 0x0002
	int 0x0010
	
	mov ax, 0x1121
	mov cx, 14
	xor bl, bl
	mov dl, 0x0001
	int 0x0010
    ret
printString:
    xor dx, dx
	
    mov ah, 0x000f
	int 0x0010
	
	mov ah, 0x0003
	int 0x0010
	
	mov cx, 44
	mov bl, 0x0007
	mov ax, 0x1301
	int 0x0010
	ret