From 3c7741bdc92b29982456f6dbb80e353577c1a628 Mon Sep 17 00:00:00 2001
From: shikhin <draumr.shikhin@gmail.com>
Date: Sun, 26 Mar 2023 05:24:39 +0530
Subject: [PATCH] Add scroll up/down buttons, space handling

---
 viewer.asm | 127 ++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 96 insertions(+), 31 deletions(-)

diff --git a/viewer.asm b/viewer.asm
index a36e0db..038a68b 100644
--- a/viewer.asm
+++ b/viewer.asm
@@ -8,7 +8,7 @@ WINDOW_STATUS_RESIZE equ 2
 
 ; Resize button, title, space, close button
 WINDOW_MIN_WIDTH equ 1 + 8 + 1 + 1
-WINDOW_MIN_HEIGHT equ 2
+WINDOW_MIN_HEIGHT equ 3
 
 ; 0x0000
 jmp near process_event
@@ -52,15 +52,9 @@ initialize:
 	mov [cur_file_address + 2], ax
 	mov [cur_file_address], bx
 	mov [beg_file_address], bx
-	shl cx, 1 ; 2
-	shl cx, 1 ; 4
-	shl cx, 1 ; 8
-	shl cx, 1 ; 16
-	shl cx, 1 ; 32
-	shl cx, 1 ; 64
-	shl cx, 1 ; 128
-	shl cx, 1 ; 256
-	shl cx, 1 ; 512
+	mov ch, cl
+	xor cl, cl
+	shl cx, 1 ; Multiply by 512
 	add bx, cx
 	mov [end_file_address], bx
 
@@ -484,7 +478,7 @@ event_click:
 			call deallocate_own_memory
 			; We don't need to call request_redraw here, since
 			; it will be called unconditionally above
-			jmp .title_bar_end
+			jmp .end
 		.not_close:
 
 		; Did the user click on the resize button?
@@ -492,7 +486,7 @@ event_click:
 		jne .not_resize
 		.resize:
 			mov byte [window_status], WINDOW_STATUS_RESIZE
-			jmp .title_bar_end
+			jmp .end
 		.not_resize:
 
 		; Clicking on the title bar signals beginning of a window
@@ -501,9 +495,46 @@ event_click:
 		mov ax, [window_x]
 		sub ax, cx
 		mov [window_move_x_offset], ax
-	.title_bar_end:
-	.not_title_bar:
+		jmp .end
 
+	.not_title_bar:
+	mov ax, [window_x]
+	add ax, [window_width]
+	dec ax
+	cmp ax, cx
+	jne .not_scroll_bar
+
+	; Scroll up button?
+	mov ax, [window_y]
+	inc ax
+	cmp ax, bx
+	jne .not_scroll_up
+	.scroll_up:
+		call file_prev_line
+		test dx, dx
+		jz .end
+
+		call render_window
+		call request_redraw
+		jmp .end
+	.not_scroll_up:
+
+	; Scroll down button?
+	add ax, [window_height]
+	dec ax
+	dec ax
+	cmp ax, bx
+	jne .not_scroll_down
+	.scroll_down:
+		call file_next_line
+		test dx, dx
+		jz .end
+
+		call render_window
+		call request_redraw
+	.not_scroll_down:
+
+	.not_scroll_bar:
 	.end:
 	pop ax
 	ret
@@ -518,23 +549,44 @@ event_click:
 event_keyboard:
 	cmp ch, 0x50 ; down key
 	jne .up_key_check
-	call file_next_line
-	test dx, dx
-	jz .ret
+	.down_key:
+		call file_next_line
+		test dx, dx
+		jz .ret
+
+		call render_window
+		call request_redraw
+		ret
 
-	call render_window
-	call request_redraw
-	
 	.up_key_check:
 	cmp ch, 0x48 ; up key
+	jne .space_check
+	.up_key:
+		call file_prev_line
+		test dx, dx
+		jz .ret
+		
+		call render_window
+		call request_redraw
+		ret
+
+	.space_check:
+	cmp cl, ' '
 	jne .ret
-	call file_prev_line
-	test dx, dx
-	jz .ret
-	
-	call render_window
-	call request_redraw
-	
+	.space:
+		; Go down eight lines
+		xor ax, ax
+		mov cx, 8
+		.loop:
+			call file_next_line
+			or ax, dx
+			loop .loop
+		test ax, ax
+		jz .ret
+
+		call render_window
+		call request_redraw
+
 	.ret:
 	ret
 
@@ -720,6 +772,19 @@ render_window:
 	add di, [window_width]
 	call print_file
 
+	add di, [window_width]
+	add di, [window_width]
+	sub di, 2
+	mov byte [di], 0x1E ; up
+
+	mov ax, [window_width]
+	mov cx, [window_height]
+	sub cx, 2
+	shl cx, 1
+	mul cx
+	add di, ax
+	mov byte [di], 0x1F ; down
+
 	pop di
 	pop si
 	pop dx
@@ -893,10 +958,10 @@ beg_file_address: dw 0
 end_file_address: dw 0
 
 window_next dw 0xffff
-window_x dw 4
-window_y dw 12
-window_width dw 32
-window_height dw 8
+window_x dw 17
+window_y dw 7
+window_width dw 52
+window_height dw 16
 
 window_mouse_released_inside db 0
 window_status db WINDOW_STATUS_NORMAL