fox32rom/background.asm

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; background routines
2022-02-12 05:44:11 +01:00
const BACKGROUND_FRAMEBUFFER: 0x80000000 ; pointer to background framebuffer
; fill the whole background with a color
; inputs:
; r0: color
; outputs:
; none
fill_background:
push r1
push r31
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mov r1, BACKGROUND_FRAMEBUFFER
mov r31, 0x0004B000 ; 640*480
fill_background_loop:
mov [r1], r0
add r1, 4
loop fill_background_loop
pop r31
pop r1
ret
; draw a filled rectangle to the background
; inputs:
; r0: X coordinate of top-left
; r1: Y coordinate of top-left
; r2: X size
; r3: Y size
; r4: color
; outputs:
; none
draw_filled_rectangle_to_background:
push r0
push r1
push r2
push r3
push r4
push r5
push r6
; calculate pointer to the framebuffer
mul r1, 2560 ; y * 2560 (640 * 4 = 2560)
mul r0, 4 ; x * 4
add r0, r1 ; y * 2560 + (x * 4)
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add r0, BACKGROUND_FRAMEBUFFER ; r0: pointer to framebuffer
mov r6, r2
mul r6, 4 ; multiply the X size by 4, since 4 bytes per pixel
draw_filled_rectangle_to_background_y_loop:
mov r5, r2 ; x counter
draw_filled_rectangle_to_background_x_loop:
mov [r0], r4
add r0, 4 ; increment framebuffer pointer
dec r5
ifnz jmp draw_filled_rectangle_to_background_x_loop ; loop if there are still more X pixels to draw
sub r0, r6 ; return to the beginning of this line
add r0, 2560 ; 640*4, increment to the next line
dec r3
ifnz jmp draw_filled_rectangle_to_background_y_loop ; loop if there are still more Y pixels to draw
pop r6
pop r5
pop r4
pop r3
pop r2
pop r1
pop r0
ret
; draw a single font tile to the background
; inputs:
; r0: tile number
; r1: X coordinate
; r2: Y coordinate
; r3: foreground color
; r4: background color
; outputs:
; none
draw_font_tile_to_background:
push r5
push r6
push r7
push r8
push r9
mov r5, standard_font_data
movz.16 r6, [standard_font_width]
movz.16 r7, [standard_font_height]
mov r8, BACKGROUND_FRAMEBUFFER
mov r9, 640
call draw_font_tile_generic
pop r9
pop r8
pop r7
pop r6
pop r5
ret
; draw text to the background
; inputs:
; r0: pointer to null-terminated string
; r1: X coordinate
; r2: Y coordinate
; r3: foreground color
; r4: background color
; outputs:
; r1: X coordinate of end of text
draw_str_to_background:
push r0
push r5
mov r5, r0
draw_str_to_background_loop:
movz.8 r0, [r5]
call draw_font_tile_to_background
inc r5
add r1, 8
cmp.8 [r5], 0x00
ifnz jmp draw_str_to_background_loop
pop r5
pop r0
ret