Tutorial 9: Child Window Controls
Download the example here.
WinMain proto :DWORD,:DWORD,:DWORD,:DWORD
include \masm32\include\windows.inc
include \masm32\include\user32.inc
include \masm32\include\kernel32.inc
includelib \masm32\lib\user32.lib
includelib \masm32\lib\kernel32.lib
.data
ClassName db "SimpleWinClass",0
AppName db "Our First Window",0
MenuName db "FirstMenu",0
ButtonClassName db "button",0
ButtonText db "My First Button",0
EditClassName db "edit",0
TestString db "Wow! I'm in an edit box now",0
.data?
hInstance HINSTANCE ?
CommandLine LPSTR ?
hwndButton HWND ?
hwndEdit HWND ?
buffer db 512 dup(?)
; buffer to store the text retrieved from the edit box
.const
ButtonID equ 1
; The control ID of the button control
EditID equ 2
; The control ID of the edit control
IDM_HELLO equ 1
IDM_CLEAR equ 2
IDM_GETTEXT equ 3
IDM_EXIT equ 4
.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_BTNFACE+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_CREATE
invoke CreateWindowEx,WS_EX_CLIENTEDGE,
ADDR EditClassName,NULL,\
WS_CHILD or WS_VISIBLE or WS_BORDER or ES_LEFT or\
ES_AUTOHSCROLL,\
50,35,200,25,hWnd,8,hInstance,NULL
mov hwndEdit,eax
invoke SetFocus, hwndEdit
invoke CreateWindowEx,NULL, ADDR
ButtonClassName,ADDR ButtonText,\
WS_CHILD or WS_VISIBLE or BS_DEFPUSHBUTTON,\
75,70,140,25,hWnd,ButtonID,hInstance,NULL
mov hwndButton,eax
.ELSEIF uMsg==WM_COMMAND
mov eax,wParam
.IF lParam==0
.IF ax==IDM_HELLO
invoke SetWindowText,hwndEdit,ADDR TestString
.ELSEIF
ax==IDM_CLEAR
invoke SetWindowText,hwndEdit,NULL
.ELSEIF
ax==IDM_GETTEXT
invoke GetWindowText,hwndEdit,ADDR buffer,512
invoke MessageBox,NULL,ADDR buffer,ADDR AppName,MB_OK
.ELSE
invoke DestroyWindow,hWnd
.ENDIF
.ELSE
.IF ax==ButtonID
shr eax,16
.IF ax==BN_CLICKED
invoke SendMessage,hWnd,WM_COMMAND,IDM_GETTEXT,0
.ENDIF
.ENDIF
.ENDIF
.ELSE
invoke DefWindowProc,hWnd,uMsg,wParam,lParam
ret
.ENDIF
xor eax,eax
ret
WndProc endp
end start
.ELSEIF uMsg==WM_COMMAND
mov eax,wParam
.IF lParam==0
Recall that a menu also sends WM_COMMAND messages to notify the window about
its state too. How can you differentiate between WM_COMMAND messages originated
from a menu or a control? Below is the answer
Low word of wParam | High word of wParam | lParam | |
Menu | Menu ID | 0 | 0 |
Control | Control ID | Notification code | Child Window Handle |
You can see that you should check lParam. If it's zero, the current WM_COMMAND message is from a menu. You cannot use wParam to differentiate between a menu and a control since the menu ID and control ID may be identical and the notification code may be zero.
.IF ax==IDM_HELLO
invoke SetWindowText,hwndEdit,ADDR TestString
.ELSEIF
ax==IDM_CLEAR
invoke SetWindowText,hwndEdit,NULL
.ELSEIF
ax==IDM_GETTEXT
invoke GetWindowText,hwndEdit,ADDR buffer,512
invoke MessageBox,NULL,ADDR buffer,ADDR AppName,MB_OK
You can put a text string into an edit box by calling SetWindowText. You clear
the content of an edit box by calling SetWindowText with NULL. SetWindowText
is a general purpose API function. You can use SetWindowText to change the caption
of a window or the text on a button.
To get the text in an edit box, you use GetWindowText.
.IF ax==ButtonID
shr eax,16
.IF ax==BN_CLICKED
invoke SendMessage,hWnd,WM_COMMAND,IDM_GETTEXT,0
.ENDIF
.ENDIF
The above code snippet deals with the condition when the user presses the button.
First, it checks the low word of wParam to see if the control ID matches that
of the button. If it is, it checks the high word of wParam to see if it is the
notification code BN_CLICKED which is sent when the button is clicked.
The interesting part is after it's certain that the notification code is BN_CLICKED.
We want to get the text from the edit box and display it in a message box. We
can duplicate the code in the IDM_GETTEXT section above but it doesn't make
sense. If we can somehow send a WM_COMMAND message with the low word of wParam
containing the value IDM_GETTEXT to our own window procedure, we can avoid code
duplication and simplify our program. SendMessage function is the answer. This
function sends any message to any window with any wParam and lParam we want.
So instead of duplicating the code, we call SendMessage with the parent window
handle, WM_COMMAND, IDM_GETTEXT, and 0. This has identical effect to selecting
"Get Text" menu item from the menu. The window procedure doesn't perceive any
difference between the two.
You should use this technique as much as possible to make your code more organized.
Last but not least, do not forget the TranslateMessage function in the message
loop. Since you must type in some text into the edit box, your program must
translate raw keyboard input into readable text. If you omit this function,
you will not be able to type anything into your edit box.