Separate calculating hand position from drawing it

dosclock.asm

@@ -79,8 +79,10 @@ mainloop:
 
 		; Draw hour hand
 		mov ax, hour_hand_len
-		mov cl, hour_hand_color
-		call draw_hand
+		mov bp, line_sx
+		call calculate_hand_position
+		mov bl, hour_hand_color
+		call draw_line
 
 		; 1 minute = 5° rotation of minute hand
 		mov ax, [minute]
@@ -94,8 +96,10 @@ mainloop:
 
 		; Draw minute hand
 		mov ax, minute_hand_len
-		mov cl, minute_hand_color
-		call draw_hand
+		mov bp, line_sx
+		call calculate_hand_position
+		mov bl, minute_hand_color
+		call draw_line
 
 		; 1 second = 5° rotation of second hand
 		mov ax, [second]
@@ -104,8 +108,10 @@ mainloop:
 
 		; Draw second hand
 		mov ax, second_hand_len
-		mov cl, second_hand_color
-		call draw_hand
+		mov  bp, line_sx
+		call calculate_hand_position
+		mov bl, second_hand_color
+		call draw_line
 
 	.unchanged:
 	hlt
@@ -135,30 +141,30 @@ clear_screen:
 ; in:
 ;  ax = hand length
 ;  bx = hand angle
-;  cl = hand color
-draw_hand:
+;  bp = points data area
+; out:
+;  [bp] = start x
+;  [bp + 2] = start y
+;  [bp + 4] = end x
+;  [bp + 6] = end y
+calculate_hand_position:
 	push ax
-	push bx
 	push dx
 
-	mov word [line_sx], midpoint_x
-	mov word [line_sy], midpoint_y
-	mov word [line_ex], midpoint_x
-	mov word [line_ey], midpoint_y
+	mov word [bp], midpoint_x
+	mov word [bp + 2], midpoint_y
+	mov word [bp + 4], midpoint_x
+	mov word [bp + 6], midpoint_y
 
 	mov dx, ax
 	call sinx
-	add [line_ex], ax
+	add [bp + 4], ax
 
 	mov ax, dx
 	call cosx
-	sub [line_ey], ax
-
-	mov bl, cl
-	call draw_line
+	sub [bp + 6], ax
 
 	pop dx
-	pop bx
 	pop ax
 	ret