Draw mouse cursor

ponydos.asm

@@ -3,6 +3,9 @@ bits 16
 
 org 0x7c00
 
+COLUMNS equ 80
+ROWS equ 25
+
 jmp 0:start
 start:
 	cld
@@ -47,7 +50,7 @@ initialize_mouse:
 	int 0x15
 	jc .error
 
-	jmp mainloop
+	jmp .done
 
 	.error:
 		; https://www.ctyme.com/intr/rb-1601.htm
@@ -55,14 +58,87 @@ initialize_mouse:
 		int 0x15
 		jmp initialize_mouse
 
-mainloop:
-	; TODO: everything
+	.done:
+
+initialize_screen:
+	mov ax, 0xb800 ; VGA text video memory
+	mov es, ax
+
+	; Clear screen with asterisks and 15-0 background-foreground
+	mov ax, 0xf000 + '*'
+	mov cx, 25*80
+	xor di, di
+	rep stosw
+
+	; Disable text cursor
+	mov dx, 0x3d4
+	mov al, 0xa
+	out dx, al
+	inc dx
+	mov al, 0x20
+	out dx, al
+
+	xor ax, ax
+	call flip_mouse_cursor
+
+mainloop:
+	mov bx, [mouse_x]
+	mov cx, [mouse_y]
+	cmp [mouse_x_old], bx
+	jne .update_cursor
+	cmp [mouse_y_old], cx
+	jne .update_cursor
 
-hang:
 	hlt
-	;mov ax, 0x0e00 + '.'
-	;int 0x10
-	jmp hang
+	jmp mainloop
+
+	.update_cursor:
+		mov ah, [mouse_x_old]
+		mov al, [mouse_y_old]
+		call flip_mouse_cursor
+		mov ah, [mouse_x]
+		mov al, [mouse_y]
+		call flip_mouse_cursor
+
+		mov [mouse_x_old], bx
+		mov [mouse_y_old], cx
+
+		jmp mainloop
+
+; in:
+;  ah = column
+;  al = row
+flip_mouse_cursor:
+	push ax
+	push bx
+	push cx
+	push es
+
+	mov bx, 0xb800
+	mov es, bx
+
+	; Column
+	xor bh, bh
+	mov bl, ah
+	shl bx, 1
+
+	; Row
+	mov cl, COLUMNS*2
+	mul cl
+	add bx, ax
+
+	; Swap foreground and background colours
+	inc bx
+	mov al, [es:bx]
+	mov cl, 4
+	ror al, cl
+	mov [es:bx], al
+
+	pop es
+	pop cx
+	pop bx
+	pop ax
+	ret
 
 Y_OVERFLOW equ 0x80
 X_OVERFLOW equ 0x40
@@ -70,8 +146,6 @@ Y_NEGATIVE equ 0x20
 X_NEGATIVE equ 0x10
 BUTTONS equ 0x03
 
-COLUMNS equ 80
-ROWS equ 25
 X_MAX_VALUE equ COLUMNS-1
 Y_MAX_VALUE equ ROWS-1
 
@@ -108,10 +182,6 @@ mouse_handler:
 			jnc .x_end
 			mov word [mouse_x], 0
 	.x_end:
-	mov ax, [mouse_x];debg
-	call hexprint16;debg
-	mov ax, 0x0e00 + ' ';debg
-	int 0x10;debg
 
 	test bl, Y_OVERFLOW
 	jnz .y_end
@@ -134,21 +204,10 @@ mouse_handler:
 			jb .y_end
 			mov word [mouse_y], Y_MAX_VALUE
 	.y_end
-	mov ax, [mouse_y];debg
-	call hexprint16;debg
-	mov ax, 0x0e00 + ' ';debg
-	int 0x10;debg
 
 	and bl, BUTTONS
 	mov [mouse_buttons], bl
 
-	mov al, [mouse_buttons];debg
-	call hexprint8;debg
-	mov ax, 0x0e00 + 13;debg
-	int 0x10;debg
-	mov ax, 0x0e00 + 10;debg
-	int 0x10;debg
-
 	pop ds
 	pop bp
 	pop bx
@@ -195,4 +254,7 @@ mouse_x resw 1
 mouse_y resw 1
 mouse_buttons resb 1
 
+mouse_x_old resw 1
+mouse_y_old resw 1
+
 _bss_end: