Rewrite mouse handler to use less code
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cb030ccf41
commit
9d3de7483e
82
ponydos.asm
82
ponydos.asm
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@ -319,8 +319,6 @@ open_file:
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Y_OVERFLOW equ 0x80
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X_OVERFLOW equ 0x40
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Y_NEGATIVE equ 0x20
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X_NEGATIVE equ 0x10
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BUTTONS equ 0x03
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X_MAX_VALUE equ 2*COLUMNS-1
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@ -328,62 +326,70 @@ Y_MAX_VALUE equ 4*ROWS-1
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mouse_handler:
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pusha
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push ds
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mov ax, cs
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mov ds, ax
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mov bp, sp
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mov bx, [bp+2*9+10] ; status
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mov bx, [bp+2*8+10] ; status
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test bl, X_OVERFLOW
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jnz .x_end
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.x:
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mov ax, [bp+2*9+8] ; X
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mov si, [cs:mouse_x]
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test bl, X_NEGATIVE
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jnz .x_negative
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.x_nonnegative:
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add [mouse_x], ax
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cmp word [mouse_x], X_MAX_VALUE
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jb .x_end
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mov word [mouse_x], X_MAX_VALUE
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jmp .x_end
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mov ax, [bp+2*8+8] ; X
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.x_negative:
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neg al
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sub [mouse_x], ax
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jnc .x_end
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mov word [mouse_x], 0
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; X and Y coördinates are stored as 9-bit signed integers
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; using two's complement notation. The high bits are called
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; "X negative" and "Y negative".
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mov ah, bl
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shl ah, 3 ; X negative is bit 4, shift it to sign position
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sar ah, 7 ; Fill entire byte with sign bit's value
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add si, ax
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;cmp si, 0
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jge .not_x_underflow
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xor si, si
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.not_x_underflow:
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cmp si, X_MAX_VALUE
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jle .not_x_overflow
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mov si, X_MAX_VALUE
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.not_x_overflow:
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mov [cs:mouse_x], si
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.x_end:
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test bl, Y_OVERFLOW
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jnz .y_end
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.y:
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mov ax, [bp+2*9+6] ; Y
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mov si, [cs:mouse_y]
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test bl, Y_NEGATIVE
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jnz .y_negative
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.y_nonnegative:
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; Y-axis is inverted
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sub [mouse_y], ax
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jnc .y_end
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mov word [mouse_y], 0
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jmp .y_end
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mov ax, [bp+2*8+6] ; Y
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.y_negative:
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neg al
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add [mouse_y], ax
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cmp word [mouse_y], Y_MAX_VALUE
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jb .y_end
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mov word [mouse_y], Y_MAX_VALUE
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mov ah, bl
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shl ah, 2 ; Y negative is bit 5
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sar ah, 7
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; Y direction is flipped compared to our coöridinate space
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sub si, ax
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;cmp si, 0
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jge .not_y_underflow
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xor si, si
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.not_y_underflow:
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cmp si, Y_MAX_VALUE
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jl .not_y_overflow
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mov si, Y_MAX_VALUE
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.not_y_overflow:
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mov [cs:mouse_y], si
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.y_end:
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and bl, BUTTONS
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mov [mouse_buttons], bl
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mov [cs:mouse_buttons], bl
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pop ds
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popa
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retf
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