fox32rom/overlay.asm

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; overlay routines
; fill a whole overlay with a color
; inputs:
; r0: color
; r1: overlay number
; outputs:
; none
fill_overlay:
push r1
push r2
push r3
push r31
mov r2, r1
or r2, 0x02000100 ; bitwise or the overlay number with the command to get the overlay size
or r1, 0x02000200 ; bitwise or the overlay number with the command to get the framebuffer pointer
in r1, r1 ; r1: overlay framebuffer poiner
in r2, r2
mov r3, r2
and r2, 0x0000FFFF ; r2: X size
sra r3, 16 ; r3: Y size
mul r2, r3
mov r31, r2
fill_overlay_loop:
mov [r1], r0
add r1, 4
loop fill_overlay_loop
pop r31
pop r3
pop r2
pop r1
ret
; draw a filled rectangle to an overlay
; inputs:
; r0: X coordinate of top-left
; r1: Y coordinate of top-left
; r2: X size
; r3: Y size
; r4: color
; r5: overlay number
; outputs:
; none
draw_filled_rectangle_to_overlay:
push r0
push r1
push r2
push r3
push r4
push r5
push r6
push r7
; calculate pointer to the framebuffer
mov r6, r5 ; r6: overlay number
or r6, 0x02000100 ; bitwise or the overlay number with the command to get the overlay size
in r7, r6
and r7, 0x0000FFFF ; mask off the height, we only need the width
mul r7, 4 ; r7: overlay width in bytes (width * 4)
mul r1, r7 ; y * width * 4
mul r0, 4 ; x * 4
add r0, r1 ; y * width * 4 + (x * 4)
or r5, 0x02000200 ; bitwise or the overlay number with the command to get the framebuffer pointer
in r5, r5
add r0, r5 ; 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_overlay_y_loop:
mov r5, r2 ; x counter
draw_filled_rectangle_to_overlay_x_loop:
mov [r0], r4
add r0, 4 ; increment framebuffer pointer
dec r5
ifnz jmp draw_filled_rectangle_to_overlay_x_loop ; loop if there are still more X pixels to draw
sub r0, r6 ; return to the beginning of this line
add r0, r7 ; increment to the next line
dec r3
ifnz jmp draw_filled_rectangle_to_overlay_y_loop ; loop if there are still more Y pixels to draw
pop r7
pop r6
pop r5
pop r4
pop r3
pop r2
pop r1
pop r0
ret
; draw a single font tile to an overlay
; inputs:
; r0: tile number
; r1: X coordinate
; r2: Y coordinate
; r3: foreground color
; r4: background color
; r5: overlay number
; outputs:
; none
draw_font_tile_to_overlay:
push r0
push r1
push r2
push r5
push r6
push r7
;movz.8 r0, r0 ; ensure the tile number is a single byte
; calculate pointer to the tile data
push r1
push r2
mov r1, 8 ; tile width
mov r2, 16 ; tile height
mul r1, r2
mul r0, r1
mul r0, 4 ; 4 bytes per pixel
add r0, font ; r0: pointer to tile data
pop r2
pop r1
; calculate pointer to the framebuffer
mov r7, r5 ; r7: overlay number
or r7, 0x02000100 ; bitwise or the overlay number with the command to get the overlay size
in r6, r7
and r6, 0x0000FFFF ; mask off the height, we only need the width
mul r6, 4 ; 4 bytes per pixel
mov r7, r6 ; r7: overlay width in bytes (width * 4)
mul r2, r7 ; y * width * 4
mul r1, 4 ; x * 4
add r1, r2 ; y * width * 4 + (x * 4)
or r5, 0x02000200 ; bitwise or the overlay number with the command to get the framebuffer pointer
in r6, r5
add r1, r6 ; r1: pointer to framebuffer
mov r6, 16 ; y counter
draw_font_tile_to_overlay_y_loop:
mov r5, 8 ; x counter
draw_font_tile_to_overlay_x_loop:
mov r2, [r0]
cmp r2, 0xFF000000
ifz jmp draw_font_tile_to_overlay_x_loop_background
; drawing foreground pixel
cmp r3, 0x00000000 ; is the foreground color supposed to be transparent?
ifz jmp draw_font_tile_to_overlay_x_loop_end
mov [r1], r3 ; draw foreground color
jmp draw_font_tile_to_overlay_x_loop_end
draw_font_tile_to_overlay_x_loop_background:
; drawing background pixel
cmp r4, 0x00000000 ; is the background color supposed to be transparent?
ifz jmp draw_font_tile_to_background_x_loop_end
mov [r1], r4 ; draw background color
draw_font_tile_to_overlay_x_loop_end:
add r0, 4 ; increment tile pointer
add r1, 4 ; increment framebuffer pointer
dec r5
ifnz jmp draw_font_tile_to_overlay_x_loop ; loop if there are still more X pixels to draw
sub r1, 32 ; 8*4, return to the beginning of this line
add r1, r7 ; increment to the next line by adding the overlay width in bytes
dec r6
ifnz jmp draw_font_tile_to_overlay_y_loop ; loop if there are still more Y pixels to draw
pop r7
pop r6
pop r5
pop r2
pop r1
pop r0
ret
; draw text on an overlay
; inputs:
; r0: pointer to null-terminated string
; r1: X coordinate
; r2: Y coordinate
; r3: foreground color
; r4: background color
; r5: overlay number
; outputs:
; r1: X coordinate of end of text
draw_str_to_overlay:
push r0
push r6
mov r6, r0
draw_str_to_overlay_loop:
movz.8 r0, [r6]
call draw_font_tile_to_overlay
inc r6
add r1, 8
cmp.8 [r6], 0x00
ifnz jmp draw_str_to_overlay_loop
pop r6
pop r0
ret
; finds the overlay with the highest priority covering the specified position
; does not check overlay 31, which is always the mouse pointer
; inputs:
; r0: X coordinate
; r1: Y coordinate
; outputs:
; r0: overlay number
find_overlay_covering_position:
; TODO:
; checks if the specified overlay is covering the specified position on screen
; the overlay can be enabled or disabled
; example:
; overlay 0 is at (0,0) and is 32x32 in size
; point (4,2) is covered by overlay 0
; point (16,16) is covered by overlay 0
; point (31,31) is covered by overlay 0
; point (32,32) is NOT covered by overlay 0, because it is outside of the overlay's area
; this works for overlays of any size, at any position on screen
; inputs:
; r0: X coordinate
; r1: Y coordinate
; r2: overlay number
; outputs:
; Z flag: set if covering, clear if not covering
check_if_overlay_covers_position:
push r0
push r1
push r3
push r4
push r5
push r6
push r7
mov r3, r2
or r3, 0x02000000 ; bitwise or the overlay number with the command to get the overlay position
in r4, r3
mov r5, r4
and r4, 0x0000FFFF ; r4: X position
sra r5, 16 ; r5: Y position
mov r3, r2
or r3, 0x02000100 ; bitwise or the overlay number with the command to get the overlay size
in r6, r3
mov r7, r6
and r6, 0x0000FFFF ; r6: width
sra r7, 16 ; r7: height
add r6, r4
add r7, r5
; (r4,r5): coordinates of top-left of the overlay
; (r6,r7): coordinates of bottom-right of the overlay
; now we need to check if:
; - (r4,r5) is greater than or equal to (r0,r1)
; and
; - (r6,r7) is less than or equal to (r0,r1)
; if carry flag is set, value is less than
; if carry flag is clear, value is greater than or equal to
cmp r0, r4
ifc jmp check_if_overlay_covers_position_fail
cmp r0, r6
ifnc jmp check_if_overlay_covers_position_fail
cmp r1, r5
ifc jmp check_if_overlay_covers_position_fail
cmp r1, r7
ifnc jmp check_if_overlay_covers_position_fail
; if we reached this point then the point is within the bounds of the overlay !!!
mov.8 r0, 0
cmp.8 r0, 0 ; set Z flag
pop r7
pop r6
pop r5
pop r4
pop r3
pop r1
pop r0
ret
check_if_overlay_covers_position_fail:
mov.8 r0, 1
cmp.8 r0, 0 ; clear Z flag
pop r7
pop r6
pop r5
pop r4
pop r3
pop r1
pop r0
ret
; checks if the specified overlay is covering the specified position on screen
; the overlay must be enabled
; example:
; overlay 0 is at (0,0) and is 32x32 in size
; point (4,2) is covered by overlay 0
; point (16,16) is covered by overlay 0
; point (31,31) is covered by overlay 0
; point (32,32) is NOT covered by overlay 0, because it is outside of the overlay's area
; this works for overlays of any size, at any position on screen
; inputs:
; r0: X coordinate
; r1: Y coordinate
; r2: overlay number
; outputs:
; Z flag: set if covering, clear if not covering
check_if_enabled_overlay_covers_position:
push r3
push r4
mov r3, r2
or r3, 0x02000300 ; bitwise or the overlay number with the command to get the overlay enable status
in r4, r3
cmp r4, 0
pop r4
pop r3
ifnz jmp check_if_enabled_overlay_covers_position_is_enabled
cmp r4, 1 ; r4 is known to be zero at this point, so compare it with 1 to clear the Z flag
ret
check_if_enabled_overlay_covers_position_is_enabled:
call check_if_overlay_covers_position
ret
; converts coordinates to be relative to the position of the specified overlay
; the overlay can be enabled or disabled
; example:
; overlay is at (16,16)
; (20,20) is specified
; (4,4) will be returned
; inputs:
; r0: X coordinate
; r1: Y coordinate
; r2: overlay number
; outputs:
; r0: relative X coordinate
; r1: relative Y coordinate
make_coordinates_relative_to_overlay:
push r2
push r3
or r2, 0x02000000 ; bitwise or the overlay number with the command to get the overlay position
in r2, r2
mov r3, r2
and r2, 0x0000FFFF ; r2: overlay X position
sra r3, 16 ; r3: overlay Y position
sub r0, r2
sub r1, r3
pop r3
pop r2
ret