From e900a60d4a51d56b14c44e77f7d284aabb3b4715 Mon Sep 17 00:00:00 2001
From: shikhin <draumr.shikhin@gmail.com>
Date: Sun, 19 Mar 2023 19:00:21 +0530
Subject: [PATCH] Fixed a bunch of bugs in mouse_handler; memoized mouse_column
 in main loop

---
 ponydos.asm | 47 ++++++++++++++++++++++++-----------------------
 1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/ponydos.asm b/ponydos.asm
index efd1a9f..b69d7dc 100644
--- a/ponydos.asm
+++ b/ponydos.asm
@@ -93,16 +93,18 @@ draw:
 	pop es
 
 	call draw_wallpaper
+	
+	mov di, mouse_column
 	call flip_mouse_cursor
 
 mainloop:
-	mov bx, [mouse_x]
+	mov bx, [di - mouse_column + mouse_x]
 	shr bx, 1
-	mov cx, [mouse_y]
+	mov cx, [di - mouse_column + mouse_y]
 	shr cx, 2
-	cmp [mouse_column], bl
+	cmp [di], bl
 	jne .update_cursor
-	cmp [mouse_row], cl
+	cmp [di - mouse_column + mouse_row], cl
 	jne .update_cursor
 
 	hlt
@@ -110,8 +112,8 @@ mainloop:
 
 	.update_cursor:
 		call flip_mouse_cursor
-		mov [mouse_column], bl
-		mov [mouse_row], cl
+		mov [di], bl
+		mov [di - mouse_column + mouse_row], cl
 		call flip_mouse_cursor
 		jmp mainloop
 
@@ -183,6 +185,7 @@ draw_wallpaper:
 	ret
 
 ; requires:
+;  di = mouse_column
 ;  ds = 0
 ;  es = 0xb800
 flip_mouse_cursor:
@@ -190,11 +193,11 @@ flip_mouse_cursor:
 
 	; Column
 	xor bh, bh
-	mov bl, [mouse_column]
+	mov bl, [di]
 	shl bx, 1
 
 	; Row
-	mov al, [mouse_row]
+	mov al, [di - mouse_column + mouse_row]
 	mov cl, COLUMNS*2
 	mul cl
 	add bx, ax
@@ -377,10 +380,9 @@ Y_MAX_VALUE equ 4*ROWS-1
 ;  cl = negative bit # in ah
 ;  dx = MAX_VALUE
 ; out
-;  mouse_x/mouse_y updated appropriately
+;  [mouse_x]/[mouse_y] updated appropriately
 ;  si = updated [mouse_x]/[mouse_y]
-;  di = di + 1
-;  clobbers ah
+;  clobbers ax
 xy_handler:
 	; X and Y coördinates are stored as 9-bit signed integers
 	; using two's complement notation. The high bits are called
@@ -408,7 +410,6 @@ xy_handler:
 	.not_overflow:
 
 	mov [cs:di], si
-	inc di
 	ret
 
 mouse_handler:
@@ -418,32 +419,32 @@ mouse_handler:
 
 	mov bx, [bp+2*8+10] ; status
 
+	xor si, si
+	mov di, mouse_x
+	mov dx, X_MAX_VALUE
+
 	test bl, X_OVERFLOW
 	jnz .x_end
 	.x:
-
-	.x_end:
-		xor si, si
-		mov di, mouse_x
 		mov ax, [bp+2*8+8]
 		mov cl, 3
-		mov dx, X_MAX_VALUE
 		call xy_handler
+	.x_end:
+	inc di
+	inc di ; mouse_y
 
 	test bl, Y_OVERFLOW
 	jnz .y_end
 	.y:
-		inc si ; won't be zero
-		inc di ; mouse_y
+		inc si ; will be non-zero
 		mov ax, [bp+2*8+6]
 		mov cl, 2
 		;mov dx
 		mov dl, Y_MAX_VALUE
 		call xy_handler
 	.y_end:
-
 	and bl, BUTTONS
-	mov [cs:di], bl ; mouse_buttons
+	mov [cs:di - mouse_y + mouse_buttons], bl
 
 	popa
 	retf
@@ -467,8 +468,8 @@ section .bss
 _bss_start:
 
 mouse_x resw 1
-mouse_y resw 1 ; mouse_x + 2
-mouse_buttons resb 1 ; mouse_y + 1
+mouse_y resw 1 ; mouse_x + 2, do not touch
+mouse_buttons resb 1
 
 mouse_column resb 1
 mouse_row resb 1