From 313453f5b364d43b4d9dae68937816292c1035f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Juhani=20Krekel=C3=A4?= <juhani@krekelä.fi>
Date: Mon, 20 Mar 2023 21:42:59 +0200
Subject: [PATCH] Implement window unhooking

---
 debug.inc          |   7 +++
 ponydos_static.inc |   1 +
 shell.asm          | 103 ++++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 106 insertions(+), 5 deletions(-)

diff --git a/debug.inc b/debug.inc
index f7be956..8845139 100644
--- a/debug.inc
+++ b/debug.inc
@@ -27,6 +27,13 @@ hexprint4:
 	pop ax
 	ret
 
+space:
+	push ax
+	mov ax, 0x0e00 + ' '
+	int 0x10
+	pop ax
+	ret
+
 hang:
 	hlt
 	jmp hang
diff --git a/ponydos_static.inc b/ponydos_static.inc
index 280b9af..acefa99 100644
--- a/ponydos_static.inc
+++ b/ponydos_static.inc
@@ -9,6 +9,7 @@ FS_FILE_MAX_SIZE equ 128
 WM_PAINT equ 0
 WM_MOUSE equ 1
 WM_KEYBOARD equ 2
+WM_UNHOOK equ 3
 
 MOUSE_PRIMARY equ 0x01
 MOUSE_SECONDARY equ 0x02
diff --git a/shell.asm b/shell.asm
index c83b9e6..d5e013b 100644
--- a/shell.asm
+++ b/shell.asm
@@ -77,7 +77,6 @@ initialize:
 	retf
 
 process_event:
-	push ax
 	push bx
 	push cx
 	push dx
@@ -106,7 +105,13 @@ process_event:
 	cmp al, WM_KEYBOARD
 	jne .not_keyboard
 	call keyboard
-	.not_keyboard
+	jmp .end
+	.not_keyboard:
+
+	cmp al, WM_UNHOOK
+	jne .not_remove
+	call unhook
+	.not_remove:
 
 	.end:
 	pop es
@@ -117,7 +122,6 @@ process_event:
 	pop dx
 	pop cx
 	pop bx
-	pop ax
 	retf
 
 paint:
@@ -142,6 +146,8 @@ mouse:
 
 	push cx
 
+	push bx
+
 	; Y
 	xor bx, bx
 	mov bl, ch
@@ -161,11 +167,15 @@ mouse:
 	cmp [si + window.height], bx
 	jle .outside
 
+	pop bx
+
 	mov si, [si + window.data]
 	add si, 18
 	test dl, MOUSE_PRIMARY
 	jz .not_clicking
 	.clicking:
+		call raise_window
+
 		mov al, '*'
 		xchg byte [si], al
 		cmp al, '*'
@@ -184,6 +194,7 @@ mouse:
 		ret
 
 	.outside:
+		pop bx
 		pop cx
 		mov bx, [si + window.next]
 		call forward_event
@@ -197,11 +208,40 @@ keyboard:
 	call request_redraw
 	ret
 
+unhook:
+	call get_window
+
+	cmp bx, cx
+	je .match
+
+	push bx
+
+	; Forward the event
+	mov bx, [si + window.next]
+	call forward_event
+
+	; Update next ID
+	; If window.next was zero, forward_event will also return zero so
+	; this is safe in all cases
+	mov [si + window.next], ax
+
+	; Return own ID to keep self in the chain
+	pop ax
+
+	ret
+
+	.match:
+		; Return next ID in the chain to unhook
+		mov ax, [si + window.next]
+		ret
+
 ; in:
 ;  bx = valid window id for this process
 ; out:
 ;  si = pointer to window's data block
 get_window:
+	push bx
+
 	mov si, cs
 	sub bx, si
 
@@ -215,6 +255,7 @@ get_window:
 	pop dx
 	pop ax
 
+	pop bx
 	ret
 
 request_redraw:
@@ -229,6 +270,50 @@ request_redraw:
 	pop es
 	ret
 
+; in:
+;  cx = window ID to unhook
+unhook_window:
+	push ax
+	push bx
+	push es
+
+	mov bx, PONYDOS_SEG
+	mov es, bx
+	mov bx, [es:GLOBAL_WINDOW_CHAIN_HEAD]
+
+	mov al, WM_UNHOOK
+	call forward_event
+
+	mov [es:GLOBAL_WINDOW_CHAIN_HEAD], ax
+
+	pop es
+	pop bx
+	pop ax
+	ret
+
+; in:
+;  bx = window ID to raise
+raise_window:
+	push cx
+	push si
+	push es
+
+	call get_window
+
+	mov cx, bx
+	call unhook_window
+
+	mov cx, PONYDOS_SEG
+	mov es, cx
+	mov cx, bx
+	xchg [es:GLOBAL_WINDOW_CHAIN_HEAD], cx
+	mov [si + window.next], cx
+
+	pop es
+	pop si
+	pop cx
+	ret
+
 ; in
 ;  cx = height of window (>= 1)
 ;  dx = width of window in characters
@@ -388,10 +473,12 @@ strlen:
 ; in:
 ;  bx = window ID
 ; out:
-;  clobbers bp
+;  ax = return value of event handler; 0 if window ID is 0
 forward_event:
+	push bp
+
 	cmp bx, 0
-	je .end
+	je .id_is_zero
 
 	push cs ; Return segment
 	mov bp, .end
@@ -404,7 +491,13 @@ forward_event:
 	push bp ; Call offset
 	retf
 
+	.id_is_zero:
+		; This gets skipped over in normal execution, because it
+		; explicitly returns to .end
+		xor ax, ax
+
 	.end:
+	pop bp
 	ret
 
 wallpaper_name db 'wallpaper.bin', 0