Fix typo

Previously programs deallocated their memory before forwarding a
message. If the forwarded message made another program allocate, this
could cause the program code to be overwritten while it is still
running.

README.md

@@ -68,16 +68,5 @@ You don't.
 
 #### How do I install PonyDOS?
 
-At the moment, PonyOS is only offered as a live floppy disk image with no
+At the moment, PonyDOS is only offered as a live floppy disk image with no
 installation option, for your safety.
-
-## TODO
-
-### Basic stuff
-
-* be able to click on asm/text files in file listing to open
-* delete the TODO from release README
-
-### Nice to have
-
-* ponysay

hello.asm

@@ -51,9 +51,14 @@ process_event:
 	push es
 
 	; On entry, ds and es will not be set correctly for us
-	mov bp, cs
-	mov ds, bp
-	mov es, bp
+	; WM_OPEN_FILE needs ds to be left-as is
+	cmp al, WM_OPEN_FILE
+	je .no_set_ds
+	push cs
+	pop ds
+	.no_set_ds:
+	push cs
+	pop es
 
 	cmp al, WM_PAINT
 	jne .not_paint
@@ -79,7 +84,21 @@ process_event:
 	jmp .end
 	.not_unhook:
 
+	cmp al, WM_OPEN_FILE
+	jne .not_open_file
+	call event_open_file
+	jmp .end
+	.not_open_file:
+
 	.end:
+	cmp byte [exiting], 0
+	je .not_exiting
+	; Once we have deallocated our own memory, we may not call any
+	; external functions that might allocate. Safest place to do the
+	; deallocation is just before returning control to our caller
+	call deallocate_own_memory
+	.not_exiting:
+
 	pop es
 	pop ds
 	pop bp
@@ -278,10 +297,7 @@ event_click:
 		jne .not_close
 		.close:
 			call unhook_self_from_window_chain
-			; Nothing can call into us again after we unhook
-			; the window, so deallocate the memory we have
-			; reserved
-			call deallocate_own_memory
+			mov byte [exiting], 1
 			; We don't need to call request_redraw here, since
 			; it will be called unconditionally above
 			jmp .title_bar_end
@@ -316,7 +332,7 @@ event_click:
 ; out:
 ;  clobbers everything
 event_keyboard:
-	; Unlike other events, keyboard events are not forwarded
+	; Unlike most other events, keyboard events are not forwarded
 	; Since we do not care about the keyboard for this app, we just
 	; swallow the event
 	ret
@@ -353,6 +369,24 @@ event_unhook:
 		mov ax, [window_next]
 		ret
 
+; in:
+;  al = WM_OPEN_FILE
+;  ds:cx = filename
+;  ds ≠ cs
+; out:
+;  ds = cs
+;  clobbers everything
+event_open_file:
+	; File open events are sent specifically to a process, so we don't
+	; need to forward it
+	; Unlike other event handlers, event_open_file is called with ds
+	; still set to calling process's segment, so that it can read the
+	; passed-in filename. For simplicity of code running after the,
+	; event handlers, we set ds to point to our own segment on return
+	push cs
+	pop ds
+	ret
+
 ; ------------------------------------------------------------------
 ; Event handler subroutines
 ; ------------------------------------------------------------------
@@ -643,6 +677,8 @@ request_redraw:
 ; Variables
 ; ------------------------------------------------------------------
 
+exiting db 0
+
 window_title db 'Hello'
 	.end:
 WINDOW_TITLE_LEN equ window_title.end - window_title

memory.asm

@@ -72,7 +72,21 @@ process_event:
 	jmp .end
 	.not_unhook:
 
+	cmp al, WM_OPEN_FILE
+	jne .not_open_file
+	call event_open_file
+	jmp .end
+	.not_open_file:
+
 	.end:
+	cmp byte [exiting], 0
+	je .not_exiting
+	; Once we have deallocated our own memory, we may not call any
+	; external functions that might allocate. Safest place to do the
+	; deallocation is just before returning control to our caller
+	call deallocate_own_memory
+	.not_exiting:
+
 	pop es
 	pop ds
 	pop bp
@@ -267,10 +281,7 @@ event_click:
 		jne .not_close
 		.close:
 			call unhook_self_from_window_chain
-			; Nothing can call into us again after we unhook
-			; the window, so deallocate the memory we have
-			; reserved
-			call deallocate_own_memory
+			mov byte [exiting], 1
 			; We don't need to call request_redraw here, since
 			; it will be called unconditionally above
 			jmp .title_bar_end
@@ -297,7 +308,7 @@ event_click:
 ; out:
 ;  clobbers everything
 event_keyboard:
-	; Unlike other events, keyboard events are not forwarded
+	; Unlike most other events, keyboard events are not forwarded
 	; Since we do not care about the keyboard for this app, we just
 	; swallow the event
 	ret
@@ -334,6 +345,24 @@ event_unhook:
 		mov ax, [window_next]
 		ret
 
+; in:
+;  al = WM_OPEN_FILE
+;  ds:cx = filename
+;  ds ≠ cs
+; out:
+;  ds = cs
+;  clobbers everything
+event_open_file:
+	; File open events are sent specifically to a process, so we don't
+	; need to forward it
+	; Unlike other event handlers, event_open_file is called with ds
+	; still set to calling process's segment, so that it can read the
+	; passed-in filename. For simplicity of code running after the,
+	; event handlers, we set ds to point to our own segment on return
+	push cs
+	pop ds
+	ret
+
 ; ------------------------------------------------------------------
 ; Event handler subroutines
 ; ------------------------------------------------------------------
@@ -530,6 +559,8 @@ request_redraw:
 ; Variables
 ; ------------------------------------------------------------------
 
+exiting db 0
+
 window_next dw 0xffff
 window_x dw 65
 window_y dw 3

ponydos.asm

@@ -8,8 +8,8 @@ bits 16
 
 org 0x7c00
 
-X_SENSITIVITY equ 1
-Y_SENSITIVITY equ 2
+X_SENSITIVITY equ 3
+Y_SENSITIVITY equ 3
 
 jmp 0:start
 
@@ -328,7 +328,8 @@ shell_name db 'shell.bin', 0
 ;  ds:si = file name
 ;  dx = non-zero => do not create new file
 ; out:
-;  ax = LBA of first sector, 0 if no space left
+;  ax = LBA of first sector, 0 if no space left or if dx non-zero and the
+;       specified file was not found
 ;  cx = length in sectors
 ;  di = dirent address (in GLOBAL_DIRENTS)
 ; [Far calls only]
@@ -386,7 +387,7 @@ open_file:
 
 	.create_file:
 		test dx, dx
-		jnz .return
+		jnz .error
 
 		; TODO: zero out the sector for this file?
 		inc word [es:di]

ponydos_static.inc

@@ -16,6 +16,7 @@ WM_PAINT equ 0
 WM_MOUSE equ 1
 WM_KEYBOARD equ 2
 WM_UNHOOK equ 3
+WM_OPEN_FILE equ 4
 
 MOUSE_PRIMARY equ 0x01
 MOUSE_SECONDARY equ 0x02

shell.asm

@@ -150,8 +150,11 @@ process_event:
 	cmp al, WM_UNHOOK
 	jne .not_remove
 	call unhook
+	jmp .end
 	.not_remove:
 
+	; We ignore WM_OPEN_FILE
+
 	.end:
 	cmp byte [open_windows], 0
 	jne .windows_open
@@ -181,7 +184,7 @@ paint:
 	call get_window
 
 	mov bx, [si + window.next]
-	call forward_event
+	call send_event
 
 	cmp si, windows + WINDOW_ID_FILE_WINDOW*window.size
 	jne .not_file_window
@@ -308,7 +311,7 @@ mouse:
 		mov cx, 0xffff
 		mov bx, [si + window.next]
 		mov al, WM_MOUSE
-		call forward_event
+		call send_event
 		ret
 
 	.outside:
@@ -316,7 +319,7 @@ mouse:
 		pop cx
 		mov bx, [si + window.next]
 		mov al, WM_MOUSE
-		call forward_event
+		call send_event
 		ret
 
 ; in:
@@ -442,10 +445,10 @@ unhook:
 
 	; Forward the event
 	mov bx, [si + window.next]
-	call forward_event
+	call send_event
 
 	; Update next ID
-	; If window.next was zero, forward_event will also return zero so
+	; If window.next was zero, send_event will also return zero so
 	; this is safe in all cases
 	mov [si + window.next], ax
 
@@ -542,49 +545,129 @@ move:
 	pop dx
 	ret
 
+; ------------------------------------------------------------------
+; Launching
+; ------------------------------------------------------------------
+
 ; out:
 ;  clobbers everything
 launch:
 	mov si, launch_filename
 
-	; Is it a .wall file?
+	; 4 letter file extension?
 	call strlen
 	cmp cx, 5
-	jb .not_wall
+	jb .less_than_5_chars
 	add si, cx
 	sub si, 5
+	; .text
+	mov di, text_extension
+	call strcmp
+	je .text_file
+	; .wall
 	mov di, wall_extension
 	call strcmp
-	jne .not_wall
+	je .wallpaper
+	.less_than_5_chars:
 
-	mov ax, cs
-	mov es, ax
-	mov si, launch_filename
-	mov di, wallpaper_name
-	mov cx, FS_DIRENT_NAME_SIZE
-	rep movsb
-
-	call set_wallpaper
-	call request_redraw
-	jmp .end
-
-	.not_wall:
-
-	; Is it a .bin file?
+	; 3 letter file extension?
 	cmp cx, 4
 	jb .not_launchable ; No, too short
 	mov si, launch_filename
 	add si, cx
 	sub si, 4
+	; .asm
+	mov di, asm_extension
+	call strcmp
+	je .text_file
+	; .txt
+	mov di, txt_extension
+	call strcmp
+	je .text_file
+	; .bin
 	mov di, bin_extension
 	call strcmp
-	jne .not_launchable ; No, wrong extension
+	jne .not_launchable ; No extension matched
 
 	mov si, launch_filename
+	call launch_binary
+
+	ret
+
+	.wallpaper:
+		mov ax, cs
+		mov es, ax
+		mov si, launch_filename
+		mov di, wallpaper_name
+		mov cx, FS_DIRENT_NAME_SIZE
+		rep movsb
+
+		call set_wallpaper
+		call request_redraw
+
+		ret
+
+	.not_launchable:
+		; Copy filename into the launch error dialog
+		mov si, launch_filename
+		call show_launch_error
+		ret
+
+	.text_file:
+		; Launch viewer.bin if it exists
+		mov si, viewer_file_name
+		call launch_binary
+		jc .viewer_not_found
+
+		; Send the WM_OPEN_FILE event to tell viewer the file we
+		; want it to open. launch_binary returned its segment in bx
+		; so we can just pass that to send_event, as window IDs are
+		; of the form segment | internal_id.
+		mov al, WM_OPEN_FILE
+		mov cx, launch_filename
+		call send_event
+
+		.viewer_not_found:
+		ret
+
+; in:
+;  si = name of file not launchable
+; out:
+;  clobbers everything
+show_launch_error:
+	mov di, launch_error_dialog.filename
+	mov cx, FS_DIRENT_NAME_SIZE-1
+	mov ah, 0xf0
+	.copy:
+		lodsb
+		test al, al
+		je .copy_end
+		stosw
+		loop .copy
+	.copy_end:
+	; Zero out the rest
+	xor al, al
+	rep stosw
+
+	; Show dialog
+	mov ax, cs
+	add ax, WINDOW_ID_LAUNCH_ERROR
+	mov si, windows + WINDOW_ID_LAUNCH_ERROR*window.size
+	call show_window
+
+	ret
+
+; in:
+;  si = name of the binary to launch
+; out:
+;  cf = error occured when launching binary
+;  bx = segment of the launched binary
+;  clobbers everything else
+launch_binary:
 	mov dx, 1 ; Don't create a new file if not found
 	call PONYDOS_SEG:SYS_OPEN_FILE
 	test ax, ax
-	jz .not_launchable
+	jz .file_not_found
 
 	push ax
 	push cx
@@ -600,14 +683,7 @@ launch:
 		jz .found_free_segment
 		inc si
 		loop .find_free_segment
-	; Display an error dialog if we can't allocate a segment
-	mov ax, cs
-	add ax, WINDOW_ID_OOM_ERROR
-	mov si, windows + WINDOW_ID_OOM_ERROR*window.size
-	call show_window
-	pop cx
-	pop ax
-	jmp .end
+	jmp .out_of_memory
 	.found_free_segment:
 	mov byte [es:si], 1 ; Mark as used
 
@@ -623,34 +699,37 @@ launch:
 	xor di, di ; Read
 	call PONYDOS_SEG:SYS_MODIFY_SECTORS
 
+	push es ; Save the segment for return value
+
 	; Transfer control to the newly loaded binary
 	push cs ; Return segment
-	mov ax, .end
+	mov ax, .success
 	push ax ; Return offset
 	push es ; Call segment
 	mov ax, PROC_INITIALIZE_ENTRYPOINT
 	push ax ; Call offset
 	retf
 
-	.end:
+	.success:
+	pop bx
+	clc
 	ret
 
-	.not_launchable:
-		; Copy filename into the launch error dialog
-		mov si, launch_filename
-		mov di, launch_error_dialog.filename
-		mov cx, FS_DIRENT_NAME_SIZE-1
-		.loop:
-			lodsb
-			stosb
-			inc di
-			loop .loop
+	.file_not_found:
+		call show_launch_error
+		jmp .error
 
-		; Show dialog
+	.out_of_memory:
+		; Display an error dialog if we can't allocate a segment
 		mov ax, cs
-		add ax, WINDOW_ID_LAUNCH_ERROR
-		mov si, windows + WINDOW_ID_LAUNCH_ERROR*window.size
+		add ax, WINDOW_ID_OOM_ERROR
+		mov si, windows + WINDOW_ID_OOM_ERROR*window.size
 		call show_window
+		pop cx
+		pop ax
+
+	.error:
+		stc
 		ret
 
 ; out:
@@ -675,7 +754,7 @@ set_wallpaper:
 ;  bx = window ID
 ; out:
 ;  ax = return value of event handler; 0 if window ID is 0
-forward_event:
+send_event:
 	push bp
 
 	cmp bx, 0
@@ -796,7 +875,7 @@ unhook_window:
 	mov bx, [es:GLOBAL_WINDOW_CHAIN_HEAD]
 
 	mov al, WM_UNHOOK
-	call forward_event
+	call send_event
 
 	mov [es:GLOBAL_WINDOW_CHAIN_HEAD], ax
 
@@ -1130,14 +1209,20 @@ strcmp:
 	ret
 
 ; ------------------------------------------------------------------
-; Variables
+; Constants
 ; ------------------------------------------------------------------
 
+asm_extension db '.asm', 0
 bin_extension db '.bin', 0
+txt_extension db '.txt', 0
+text_extension db '.text', 0
 wall_extension db '.wall', 0
 
-wallpaper_name db 'ponydos.wall'
-	times FS_DIRENT_NAME_SIZE-12 db 0
+viewer_file_name db 'viewer.bin', 0
+
+; ------------------------------------------------------------------
+; Variables
+; ------------------------------------------------------------------
 
 disk_icon:
 	db 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f, 0x00, 0x0f
@@ -1171,6 +1256,9 @@ windows:
 
 open_windows db 0
 
+wallpaper_name db 'ponydos.wall'
+	times FS_DIRENT_NAME_SIZE-12 db 0
+
 launch_filename times FS_DIRENT_NAME_SIZE db 0
 
 section .bss

viewer.asm

@@ -51,9 +51,14 @@ process_event:
 	push es
 
 	; On entry, ds and es will not be set correctly for us
-	mov bp, cs
-	mov ds, bp
-	mov es, bp
+	; WM_OPEN_FILE needs ds to be left-as is
+	cmp al, WM_OPEN_FILE
+	je .no_set_ds
+	push cs
+	pop ds
+	.no_set_ds:
+	push cs
+	pop es
 
 	cmp al, WM_PAINT
 	jne .not_paint
@@ -79,7 +84,18 @@ process_event:
 	jmp .end
 	.not_unhook:
 
+	cmp al, WM_OPEN_FILE
+	jne .not_open_file
+	call event_open_file
+	jmp .end
+	.not_open_file:
+
 	.end:
+	cmp byte [exiting], 0
+	je .not_exiting
+	call deallocate_own_memory
+	.not_exiting:
+
 	pop es
 	pop ds
 	pop bp
@@ -579,7 +595,7 @@ event_click:
 		jne .not_cancel
 		.cancel:
 			call unhook_self_from_window_chain
-			call deallocate_own_memory
+			mov byte [exiting], 1
 			jmp .end
 		.not_cancel:
 		cmp byte [bx], OK_COLOR
@@ -735,6 +751,39 @@ event_unhook:
 		mov ax, [window_next]
 		ret
 
+; in:
+;  al = WM_OPEN_FILE
+;  ds:cx = filename
+;  ds ≠ cs
+; out:
+;  ds = cs
+;  clobbers everything
+event_open_file:
+	; Copy the file name over
+	mov si, cx
+	mov di, [es:cur_filename_address]
+	.copy_filename:
+		lodsb
+		test al, al
+		jz .copy_end
+
+		stosb
+		inc di
+		jmp .copy_filename
+	.copy_end:
+	mov [es:cur_filename_address], di
+
+	; Set ds to be as expected by most of the program
+	push cs
+	pop ds
+
+	; Mark that the filename came from WM_OPEN_FILE
+	mov byte [filename_from_wm_open_file], 1
+
+	call filename_ok
+
+	ret
+
 ; ------------------------------------------------------------------
 ; Event handler subroutines
 ; ------------------------------------------------------------------
@@ -742,15 +791,20 @@ event_unhook:
 ; out:
 ;  clobbers si, di, cx
 close_window:
+	; If filename was from WM_OPEN_FILE event instead of user input,
+	; exit the app instead of going to name input dialog
+	cmp byte [filename_from_wm_open_file], 0
+	jne .exit_app
 	cmp word [window.data_address], oom_window_data
 	je .error_window
 	cmp word [window.data_address], ood_window_data
 	je .error_window
-	.not_error_window:
-		; Shut off app
+
+	.exit_app:
 		call unhook_self_from_window_chain
-		call deallocate_own_memory
+		mov byte [exiting], 1
 		ret
+
 	.error_window:
 		mov si, filename_window
 		mov di, window
@@ -1116,10 +1170,13 @@ request_redraw:
 ; Variables
 ; ------------------------------------------------------------------
 
+filename_from_wm_open_file db 0
+exiting db 0
+
 window_title times FS_DIRENT_NAME_SIZE db 0
 
-cur_file_address: dw 0 ; Segment
-	dw 0
+cur_file_address: dw 0
+	dw 0 ; Segment
 beg_file_address dw 0
 end_file_address dw 0