Tutorial 11: More about Dialog Box
Download the dialog box examples here and here. Download Common Dialog Box example here.
GetOpenFileName proto lpofn:DWORDYou can see that it receives only one parameter, a pointer to an OPENFILENAME structure. The return value TRUE means the user selected a file to open, it's FALSE otherwise. We will look at OPENFILENAME structure next.
OPENFILENAME STRUCTLet's see the meaning of the frequently used members.lStructSize DWORD ?OPENFILENAME ENDS
hwndOwner HWND ?
hInstance HINSTANCE ?
lpstrFilter LPCSTR ?
lpstrCustomFilter LPSTR ?
nMaxCustFilter DWORD ?
nFilterIndex DWORD ?
lpstrFile LPSTR ?
nMaxFile DWORD ?
lpstrFileTitle LPSTR ?
nMaxFileTitle DWORD ?
lpstrInitialDir LPCSTR ?
lpstrTitle LPCSTR ?
Flags DWORD ?
nFileOffset WORD ?
nFileExtension WORD ?
lpstrDefExt LPCSTR ?
lCustData LPARAM ?
lpfnHook DWORD ?
lpTemplateName LPCSTR ?
lStructSize | The size of the OPENFILENAME structure , in bytes |
hwndOwner | The window handle of the open file dialog box. |
hInstance | Instance handle of the application that creates the open file dialog box |
lpstrFilter | The filter strings in the format of pairs of null terminated strings.
The first string in each pair is the description. The second string is
the filter pattern. for example: FilterString db "All Files (*.*)",0, "*.*",0 db "Text Files (*.txt)",0,"*.txt",0,0 Note that only the pattern in the second string in each pair is actually used by Windows to filter out the files. Also noted that you have to put an extra 0 at the end of the filter strings to denote the end of it. |
nFilterIndex | Specify which pair of the filter strings will be initially used when the open file dialog is first displayed. The index is 1-based, that is the first pair is 1, the second pair is 2 and so on. So in the above example, if we specify nFilterIndex as 2, the second pattern, "*.txt" will be used. |
lpstrFile | Pointer to the buffer that contains the filename used to initialize
the filename edit control on the dialog box. The buffer should be at least
260 bytes long. After the user selects a file to open, the filename with full path is stored in this buffer. You can extract the information from it later. |
nMaxFile | The size of the lpstrFile buffer. |
lpstrTitle | Pointer to the title of the open file dialog box |
Flags | Determine the styles and characteristics of the dialog box. |
nFileOffset | After the user selects a file to open, this member contains the index to the first character of the actual filename. For example, if the full name with path is "c:\windows\system\lz32.dll", the this member will contain the value 18. |
nFileExtension | After the user selects a file to open, this member contains the index to the first character of the file extension |
.386
.model flat,stdcall
option casemap:none
WinMain proto :DWORD,:DWORD,:DWORD,:DWORD
include \masm32\include\windows.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
include \masm32\include\comdlg32.inc
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
includelib \masm32\lib\comdlg32.lib
.const
IDM_OPEN equ 1
IDM_EXIT equ 2
MAXSIZE equ 260
OUTPUTSIZE equ 512
.data
ClassName db "SimpleWinClass",0
AppName db "Our Main Window",0
MenuName db "FirstMenu",0
ofn OPENFILENAME <>
FilterString db "All Files",0,"*.*",0
db "Text Files",0,"*.txt",0,0
buffer db MAXSIZE dup(0)
OurTitle db "-=Our First Open File Dialog Box=-: Choose the file to open",0
FullPathName db "The Full Filename with Path is: ",0
FullName db "The Filename is: ",0
ExtensionName db "The Extension is: ",0
OutputString db OUTPUTSIZE dup(0)
CrLf db 0Dh,0Ah,0
.data?
hInstance HINSTANCE ?
CommandLine LPSTR ?
.code
start:
invoke GetModuleHandle, NULL
mov hInstance,eax
invoke GetCommandLine
mov CommandLine,eax
invoke WinMain, hInstance,NULL,CommandLine, SW_SHOWDEFAULT
invoke ExitProcess,eax
WinMain proc hInst:HINSTANCE,hPrevInst:HINSTANCE,CmdLine:LPSTR,CmdShow:DWORD
LOCAL wc:WNDCLASSEX
LOCAL msg:MSG
LOCAL hwnd:HWND
mov wc.cbSize,SIZEOF WNDCLASSEX
mov wc.style, CS_HREDRAW or CS_VREDRAW
mov wc.lpfnWndProc, OFFSET WndProc
mov wc.cbClsExtra,NULL
mov wc.cbWndExtra,NULL
push hInst
pop wc.hInstance
mov wc.hbrBackground,COLOR_WINDOW+1
mov wc.lpszMenuName,OFFSET MenuName
mov wc.lpszClassName,OFFSET ClassName
invoke LoadIcon,NULL,IDI_APPLICATION
mov wc.hIcon,eax
mov wc.hIconSm,eax
invoke LoadCursor,NULL,IDC_ARROW
mov wc.hCursor,eax
invoke RegisterClassEx, addr wc
invoke CreateWindowEx,WS_EX_CLIENTEDGE,ADDR ClassName,ADDR
AppName,\
WS_OVERLAPPEDWINDOW,CW_USEDEFAULT,\
CW_USEDEFAULT,300,200,NULL,NULL,\
hInst,NULL
mov hwnd,eax
invoke ShowWindow, hwnd,SW_SHOWNORMAL
invoke UpdateWindow, hwnd
.WHILE TRUE
invoke GetMessage, ADDR msg,NULL,0,0
.BREAK .IF (!eax)
invoke TranslateMessage, ADDR
msg
invoke DispatchMessage, ADDR msg
.ENDW
mov eax,msg.wParam
ret
WinMain endp
WndProc proc hWnd:HWND, uMsg:UINT, wParam:WPARAM, lParam:LPARAM
.IF uMsg==WM_DESTROY
invoke PostQuitMessage,NULL
.ELSEIF uMsg==WM_COMMAND
mov eax,wParam
.if ax==IDM_OPEN
mov ofn.lStructSize,SIZEOF
ofn
push hWnd
pop
ofn.hwndOwner
push hInstance
pop
ofn.hInstance
mov
ofn.lpstrFilter, OFFSET FilterString
mov
ofn.lpstrFile, OFFSET buffer
mov
ofn.nMaxFile,MAXSIZE
mov
ofn.Flags, OFN_FILEMUSTEXIST or \
OFN_PATHMUSTEXIST or OFN_LONGNAMES or\
OFN_EXPLORER or OFN_HIDEREADONLY
mov
ofn.lpstrTitle, OFFSET OurTitle
invoke
GetOpenFileName, ADDR ofn
.if eax==TRUE
invoke lstrcat,offset OutputString,OFFSET FullPathName
invoke lstrcat,offset OutputString,ofn.lpstrFile
invoke lstrcat,offset OutputString,offset CrLf
invoke lstrcat,offset OutputString,offset FullName
mov eax,ofn.lpstrFile
push ebx
xor ebx,ebx
mov bx,ofn.nFileOffset
add eax,ebx
pop ebx
invoke lstrcat,offset OutputString,eax
invoke lstrcat,offset OutputString,offset CrLf
invoke lstrcat,offset OutputString,offset ExtensionName
mov eax,ofn.lpstrFile
push ebx
xor ebx,ebx
mov bx,ofn.nFileExtension
add eax,ebx
pop ebx
invoke lstrcat,offset OutputString,eax
invoke MessageBox,hWnd,OFFSET OutputString,ADDR AppName,MB_OK
invoke RtlZeroMemory,offset OutputString,OUTPUTSIZE
.endif
.else
invoke
DestroyWindow, hWnd
.endif
.ELSE
invoke DefWindowProc,hWnd,uMsg,wParam,lParam
ret
.ENDIF
xor eax,eax
ret
WndProc endp
end start
We fill in the routine members of ofn structures.
mov ofn.lpstrFilter, OFFSET FilterString
This FilterString is the filename filter that we specify as follows:
FilterString db "All Files",0,"*.*",0Note that All four strings are zero terminated. The first string is the description of the following string. The actual pattern is the even number string, in this case, "*.*" and "*.txt". Actually we can specify any pattern we want here. We MUST put an extra zero after the last pattern string to denote the end of the filter string. Don't forget this else your dialog box will behave strangely.
db "Text Files",0,"*.txt",0,0
mov
ofn.lpstrFile, OFFSET buffer
mov
ofn.nMaxFile,MAXSIZE
We specify where the dialog box will put the filename that the user selects. Note that we must specify its size in nMaxFile member. We can later extract the filename from this buffer.
mov
ofn.Flags, OFN_FILEMUSTEXIST or \
OFN_PATHMUSTEXIST or OFN_LONGNAMES or\
OFN_EXPLORER or OFN_HIDEREADONLY
Flags specifies the characteristics of the dialog box.
OFN_FILEMUSTEXIST and OFN_PATHMUSTEXIST flags demand that the filename
and path that the user types in the filename edit control MUST exist.
OFN_LONGNAMES flag tells the dialog box to show long filenames.
OFN_EXPLORER flag specifies that the appearance of the dialog box must be explorer-like.
OFN_HIDEREADONLY flag hides the read-only checkbox on the dialog box.
There are many more flags that you can use. Consult your Win32 API reference.
mov ofn.lpstrTitle, OFFSET OurTitle
Specify the title of the dialog box.
invoke GetOpenFileName, ADDR ofn
Call the GetOpenFileName function. Passing the pointer to the ofn structure
as its parameter.
At this time, the open file dialog box is displayed on the screen. The function
will not return until the user selects a file to open or presses the cancel
button or closes the dialog box.
It 'll return the value TRUE in eax if the user selects a file to open. It returns
FALSE otherwise.
.if eax==TRUE
invoke lstrcat,offset OutputString,OFFSET FullPathName
invoke lstrcat,offset OutputString,ofn.lpstrFile
invoke lstrcat,offset OutputString,offset CrLf
invoke lstrcat,offset OutputString,offset FullName
In case the user selects a file to open, we prepare an output string to be displayed in a message box. We allocate a block of memory in OutputString variable and then we use an API function, lstrcat, to concatenate the strings together. In order to put the strings into several lines, we must separate each line with a carriage return-line feed pair.
mov eax,ofn.lpstrFile
push ebx
xor ebx,ebx
mov bx,ofn.nFileOffset
add eax,ebx
pop ebx
invoke lstrcat,offset OutputString,eax
The above lines require some explanation. nFileOffset contains the index into the ofn.lpstrFile. But you cannot add them together directly since nFileOffset is a WORD-sized variable and lpstrFile is a DWORD-sized one. So I have to put the value of nFileOffset into the low word of ebx and add it to the value of lpstrFile.
invoke MessageBox,hWnd,OFFSET OutputString,ADDR AppName,MB_OK
We display the string in a message box.
invoke RtlZerolMemory,offset OutputString,OUTPUTSIZE
We must *clear* the OutputString before we can fill in another string. So we
use RtlZeroMemory function to do the job.