ASM Community

hi,all
in one example of tutorial 11,he create a modeless dialog box use below code

invoke CreateDialogParam,hInstance, addr DlgName,hWnd,OFFSET DlgProc,NULL

mov hwndDlg,eax

but made the produce as below which to process model dialog box's message.

DlgProc PROC hWnd:HWND,iMsg:DWORD,wParam:WPARAM, lParam:LPARAM

        .if iMsg==WM_INITDIALOG

		invoke GetDlgItem,hWnd,IDC_EDIT

		invoke SetFocus,eax

        .elseif iMsg==WM_CLOSE

		invoke EndDialog,hWnd,NULL

		mov hwndDlg,0

        .elseif iMsg==WM_COMMAND

		mov eax,wParam

		mov edx,eax

		shr edx,16

		.if dx==BN_CLICKED

			.if eax==IDC_EXIT

				invoke SendMessage,hWnd,WM_CLOSE,NULL,NULL

			.elseif eax==IDC_BUTTON

				invoke SetDlgItemText,hWnd,IDC_EDIT,ADDR TestString

			.endif

		.endif		   

        .else

		mov eax,FALSE

		ret

        .endif

        mov  eax,TRUE

        ret

DlgProc endp

it seems wrong,but the code run well?that puzzled me.

The code has some problems.

invoke CreateDialogParam,hInstance, addr DlgName,hWnd,OFFSET DlgProc,NULL

ADDR should be used when using INVOKE.

        .if iMsg==WM_INITDIALOG

      invoke GetDlgItem,hWnd,IDC_EDIT

      invoke SetFocus,eax 

Should then return FALSE, not TRUE.

        .elseif iMsg==WM_CLOSE

		invoke EndDialog,hWnd,NULL



		mov hwndDlg,0

Should close the dialog using DestroyWindow(), not EndDialog().

        .elseif iMsg==WM_COMMAND

		mov eax,wParam

		mov edx,eax

		shr edx,16

		.if dx==BN_CLICKED

			.if eax==IDC_EXIT

				invoke SendMessage,hWnd,WM_CLOSE,NULL,NULL

Should compare AX, not EAX. Should probably use PostMessage() instead of SendMessage(). Also missing two .elses to return FALSE.

Some of these comments are not correct. You can use OFFSET in an invoke call with no problems as long as the data IS an OFFSET. An OFFSET in code is nothing more than a 32 bit address of the OFFSET of the data in the EXE file, usually but not always in the .DATA section.

The value returned from the WM_INITDIALOG processing depends on if you want to set the focus to the first control in the dialog box or not. Either true OR false are valid depending on the code design.

Even though CreateDialogParam is a modeless dialog function call, if it has no parent, it behaves no differently to a modal dialog box with no parent and you normally close a modal dialog procedure with EndDialog. As it works on versions from win95 up, it appears to be OK and version safe.

Windows code has always had various methods of handling windows. Iczelion's code has proven reliable over many years and he was well aware of the range of variation available.

i find some words in msdn as below:

"
The dialog box procedure should return TRUE to direct the system to set the keyboard focus to the control specified by wParam. Otherwise, it should return FALSE to prevent the system from setting the default keyboard focus.
"


if we return true,what control will the system set focus to?

"default keyboard focus" defined with us in resource file or
microsoft windows?

geegle,

Just pick which return value you want depending on what you want to do, its simple enough. Either set the 1st control focus as a default or manually set the forus with the API.

"invoke" syntax can easily handle a single DWORD value and this is what OFFSET delivers in 32 bit mode. You don't need to determine between ADDR and OFFSET if you know the value is an offset in the file.

All dialogs are originally designed to work as child windows as per documentation, use them without a parent handle and you change the behaviour. When a modal dialog has no parent so it cannot behave as a modal dialog. This is where the distinction breaks down.

The notion of "correct" here is in itself incorrect as the documentation does not handle the case of either type of dialog as a main window but as a child window of another window. Iczelion had no problems distinguishing between the two types, he just happened to know how they behaved when used outside of their documented behaviour.

We also can use DestroyWindow to end a model dialogbox which have
no parent.