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global find_mode
global best_video_mode
vbe_info_block:
.signature db "VBE2" ; indicate support for VBE 2.0+
.version dw 0
.oem dd 0
.capabilities dd 0
.video_modes dd 0
.video_memory dw 0
.software_rev dw 0
.vendor dd 0
.product_name dd 0
.product_rev dd 0
.reserved times 222 db 0
.oem_data times 256 db 0
mode_info_block:
.attributes dw 0
.window_a db 0
.window_b db 0
.granularity dw 0
.window_size dw 0
.segment_a dw 0
.segment_b dw 0
.win_func_ptr dd 0
.pitch dw 0
.width dw 0
.height dw 0
.w_char db 0
.y_char db 0
.planes db 0
.bpp db 0
.banks db 0
.memory_model db 0
.bank_size db 0
.image_pages db 0
.reserved0 db 0
.red_mask db 0
.red_position db 0
.green_mask db 0
.green_position db 0
.blue_mask db 0
.blue_position db 0
.reserved_mask db 0
.reserved_position db 0
.direct_color_attributes db 0
.framebuffer dd 0
.off_screen_mem_off dd 0
.off_screen_mem_size dw 0
.reserved1 times 206 db 0
best_video_mode:
.bpp db 0
.height dw 0
.width dw 0
.mode dw 0
.framebuffer dd 0
.bytes_per_line dw 0
.bytes_per_pixel dd 0
.x_cur_max dw 0
.y_cur_max dw 0
segments dw 0
offset dw 0
mode dw 0
width equ 1024
height equ 768
bpp equ 32
search_video_mode:
[bits 16]
push es
mov ax, 0x4F00
mov di, vbe_info_block
int 0x10
pop es
mov ax, word [vbe_info_block.video_modes]
mov [offset], ax
mov ax, word [vbe_info_block.video_modes+2]
mov [segments], ax
mov ax, [segments]
mov fs, ax
mov si, [offset]
mov cx, 1
push cx
find_mode:
mov dx, [fs:si]
add si, 2
mov [offset], si
mov [mode], dx
mov ax, 0
mov fs, ax
push es
mov ax, 0x4F01
mov cx, [mode]
mov di, mode_info_block
int 0x10
pop es
cmp ax, 0x004F
pop cx
cmp cx, 4
je reset_counter
inc cx
push cx
check_mode:
mov cx, 0
mov bx, [best_video_mode.width]
cmp bx, [mode_info_block.width]
jl save_and_continue
je compare_height
jmp next_mode
compare_height:
mov bx, [best_video_mode.height]
cmp bx, [mode_info_block.height]
jl save_and_continue
je compare_bpp
jmp next_mode
compare_bpp:
mov dx, [best_video_mode.bpp]
mov ax, [mode_info_block.bpp]
and ax, 11111111b
cmp dx, ax
jl save_and_continue
jmp next_mode
save_and_continue:
mov bx, [mode_info_block.width]
mov [best_video_mode.width], bx
shr bx,3
dec bx
mov [best_video_mode.x_cur_max], bx
mov bx, [mode_info_block.height]
mov [best_video_mode.height], bx
shr bx, 4
dec bx
mov word [best_video_mode.y_cur_max], ax
mov ebx, 0
mov bl, [mode_info_block.bpp]
mov byte [best_video_mode.bpp], bl
shr ebx, 3
mov dword [best_video_mode.bytes_per_pixel], ebx
mov bx, [mode]
mov [best_video_mode.mode], bx
mov ebx, [mode_info_block.framebuffer]
mov dword[best_video_mode.framebuffer], ebx
mov bx, [mode_info_block.pitch]
mov word [best_video_mode.bytes_per_line],bx
jmp next_mode
pop es
jmp $
new_line_and_next_mode:
mov cx,1
push cx
jmp next_mode
reset_counter:
mov cx, 1
push cx
jmp check_mode
set_mode:
push es
mov ax, 0x4F02
mov bx, [best_video_mode.mode]
or bx, 0x4000
mov di, 0
int 0x10
pop es
cmp ax, 0x4F
clc
next_mode:
mov ax, [segments]
mov fs, ax
mov si, [offset]
jmp find_mode
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