MessageBox
The MessageBox function creates,displays,and operates a message box,The message box contains an application-defined message and title,plus any combination of predefined icons and push buttons,
int MessageBox(
HWND hWnd, // handle of owner window
LPCTSTR lpText, // address of text in message box
LPCTSTR lpCaption, // address of title of message box
UINT uType // style of message box
);
Parameters
hWnd
Identifies the owner window of the message box to be created,If this parameter is NULL,the message box has no owner window,
lpText
Points to a null-terminated string containing the message to be displayed,
lpCaption
Points to a null-terminated string used for the dialog box title,If this parameter is NULL,the default title Error is used,
uType
Specifies the contents and behavior of the dialog box,This parameter can be a combination of the following values,
Value Meaning
MB_ABORTRETRYIGNORE The message box contains three push buttons,Abort,Retry,and Ignore.
MB_APPLMODAL The user must respond to the message box before continuing work in the window identified by the hWnd parameter,However,the user can move to the windows of other applications and work in those windows,Depending on the hierarchy of windows in the application,the user may be able to move to other windows within the application,All child windows of the parent of the message box are automatically disabled,but popup windows are not,MB_APPLMODAL is the default value if neither MB_SYSTEMMODAL nor MB_TASKMODAL is specified.
MB_DEFAULT_DESKTOP_ONLY The desktop currently receiving input must be a default desktop; otherwise,the function fails,A default desktop is one an application runs on after the user has logged on.
MB_DEFBUTTON1 The first button is the default button,Note that the first button is always the default unless MB_DEFBUTTON2,MB_DEFBUTTON3,or MB_DEFBUTTON4 is specified.
MB_DEFBUTTON2 The second button is a default button.
MB_DEFBUTTON3 The third button is a default button.
MB_DEFBUTTON4 The fourth button is a default button.
MB_HELP Windows 95,Adds a Help button to the message box,Choosing the Help button or pressing F1 generates a Help event.
MB_ICONASTERISK Same as MB_ICONINFORMATION.
MB_ICONERROR Windows 95,Same as MB_ICONHAND.
MB_ICONEXCLAMATION An exclamation-point icon appears in the message box.
MB_ICONHAND Same as MB_ICONSTOP.
MB_ICONINFORMATION An icon consisting of a lowercase letter i in a circle appears in the message box.
MB_ICONQUESTION A question-mark icon appears in the message box.
MB_ICONSTOP A stop-sign icon appears in the message box.
MB_ICONWARNING Windows 95,Same as MB_ICONEXCLAMATION.
MB_OK The message box contains one push button,OK.
MB_OKCANCEL The message box contains two push buttons,OK and Cancel.
MB_RETRYCANCEL The message box contains two push buttons,Retry and Cancel.
MB_RIGHT Windows 95,The text is right-justified.
MB_RTLREADING Windows 95,Displays message and caption text using right-to-left reading order on Hebrew and Arabic systems,
MB_SERVICE_NOTIFICATION Windows NT,The caller is a service notifying the user of an event,The function displays a message box on the current active desktop,even if there is no user logged on to the computer.If this flag is set,the hWnd parameter must be NULL,This is so the message box can appear on a desktop other than the desktop corresponding to the hWnd.
MB_SETFOREGROUND The message box becomes the foreground window,Internally,Windows calls the SetForegroundWindow function for the message box.
MB_SYSTEMMODAL All applications are suspended until the user responds to the message box,Unless the application specifies MB_ICONHAND,the message box does not become modal until after it is created; consequently,the owner window and other windows continue to receive messages resulting from its activation,Use system-modal message boxes to notify the user of serious,potentially damaging errors that require immediate attention (for example,running out of memory).
MB_TASKMODAL Same as MB_APPLMODAL except that all the top-level windows belonging to the current task are disabled if the hWnd parameter is NULL,Use this flag when the calling application or library does not have a window handle available but still needs to prevent input to other windows in the current application without suspending other applications.
MB_YESNO The message box contains two push buttons,Yes and No.
MB_YESNOCANCEL The message box contains three push buttons,Yes,No,and Cancel.
Return Value
The return value is zero if there is not enough memory to create the message box.
If the function succeeds,the return value is one of the following menu-item values returned by the dialog box,
Value Meaning
IDABORT Abort button was selected.
IDCANCEL Cancel button was selected.
IDIGNORE Ignore button was selected.
IDNO No button was selected.
IDOK OK button was selected.
IDRETRY Retry button was selected.
IDYES Yes button was selected.
If a message box has a Cancel button,the function returns the IDCANCEL value if either the ESC key is pressed or the Cancel button is selected,If the message box has no Cancel button,pressing ESC has no effect,
Remarks
When you use a system-modal message box to indicate that the system is low on memory,the strings pointed to by the lpText and lpCaption parameters should not be taken from a resource file,because an attempt to load the resource may fail,
When an application calls MessageBox and specifies the MB_ICONHAND and MB_SYSTEMMODAL flags for the uType parameter,Windows displays the resulting message box regardless of available memory,When these flags are specified,Windows limits the length of the message box text to three lines,Windows does not automatically break the lines to fit in the message box,however,so the message string must contain carriage returns to break the lines at the appropriate places,
If you create a message box while a dialog box is present,use the handle of the dialog box as the hWnd parameter,The hWnd parameter should not identify a child window,such as a control in a dialog box,
Windows 95 only,The system can support a maximum of 16,364 window handles.
The MessageBox function creates,displays,and operates a message box,The message box contains an application-defined message and title,plus any combination of predefined icons and push buttons,
int MessageBox(
HWND hWnd, // handle of owner window
LPCTSTR lpText, // address of text in message box
LPCTSTR lpCaption, // address of title of message box
UINT uType // style of message box
);
Parameters
hWnd
Identifies the owner window of the message box to be created,If this parameter is NULL,the message box has no owner window,
lpText
Points to a null-terminated string containing the message to be displayed,
lpCaption
Points to a null-terminated string used for the dialog box title,If this parameter is NULL,the default title Error is used,
uType
Specifies the contents and behavior of the dialog box,This parameter can be a combination of the following values,
Value Meaning
MB_ABORTRETRYIGNORE The message box contains three push buttons,Abort,Retry,and Ignore.
MB_APPLMODAL The user must respond to the message box before continuing work in the window identified by the hWnd parameter,However,the user can move to the windows of other applications and work in those windows,Depending on the hierarchy of windows in the application,the user may be able to move to other windows within the application,All child windows of the parent of the message box are automatically disabled,but popup windows are not,MB_APPLMODAL is the default value if neither MB_SYSTEMMODAL nor MB_TASKMODAL is specified.
MB_DEFAULT_DESKTOP_ONLY The desktop currently receiving input must be a default desktop; otherwise,the function fails,A default desktop is one an application runs on after the user has logged on.
MB_DEFBUTTON1 The first button is the default button,Note that the first button is always the default unless MB_DEFBUTTON2,MB_DEFBUTTON3,or MB_DEFBUTTON4 is specified.
MB_DEFBUTTON2 The second button is a default button.
MB_DEFBUTTON3 The third button is a default button.
MB_DEFBUTTON4 The fourth button is a default button.
MB_HELP Windows 95,Adds a Help button to the message box,Choosing the Help button or pressing F1 generates a Help event.
MB_ICONASTERISK Same as MB_ICONINFORMATION.
MB_ICONERROR Windows 95,Same as MB_ICONHAND.
MB_ICONEXCLAMATION An exclamation-point icon appears in the message box.
MB_ICONHAND Same as MB_ICONSTOP.
MB_ICONINFORMATION An icon consisting of a lowercase letter i in a circle appears in the message box.
MB_ICONQUESTION A question-mark icon appears in the message box.
MB_ICONSTOP A stop-sign icon appears in the message box.
MB_ICONWARNING Windows 95,Same as MB_ICONEXCLAMATION.
MB_OK The message box contains one push button,OK.
MB_OKCANCEL The message box contains two push buttons,OK and Cancel.
MB_RETRYCANCEL The message box contains two push buttons,Retry and Cancel.
MB_RIGHT Windows 95,The text is right-justified.
MB_RTLREADING Windows 95,Displays message and caption text using right-to-left reading order on Hebrew and Arabic systems,
MB_SERVICE_NOTIFICATION Windows NT,The caller is a service notifying the user of an event,The function displays a message box on the current active desktop,even if there is no user logged on to the computer.If this flag is set,the hWnd parameter must be NULL,This is so the message box can appear on a desktop other than the desktop corresponding to the hWnd.
MB_SETFOREGROUND The message box becomes the foreground window,Internally,Windows calls the SetForegroundWindow function for the message box.
MB_SYSTEMMODAL All applications are suspended until the user responds to the message box,Unless the application specifies MB_ICONHAND,the message box does not become modal until after it is created; consequently,the owner window and other windows continue to receive messages resulting from its activation,Use system-modal message boxes to notify the user of serious,potentially damaging errors that require immediate attention (for example,running out of memory).
MB_TASKMODAL Same as MB_APPLMODAL except that all the top-level windows belonging to the current task are disabled if the hWnd parameter is NULL,Use this flag when the calling application or library does not have a window handle available but still needs to prevent input to other windows in the current application without suspending other applications.
MB_YESNO The message box contains two push buttons,Yes and No.
MB_YESNOCANCEL The message box contains three push buttons,Yes,No,and Cancel.
Return Value
The return value is zero if there is not enough memory to create the message box.
If the function succeeds,the return value is one of the following menu-item values returned by the dialog box,
Value Meaning
IDABORT Abort button was selected.
IDCANCEL Cancel button was selected.
IDIGNORE Ignore button was selected.
IDNO No button was selected.
IDOK OK button was selected.
IDRETRY Retry button was selected.
IDYES Yes button was selected.
If a message box has a Cancel button,the function returns the IDCANCEL value if either the ESC key is pressed or the Cancel button is selected,If the message box has no Cancel button,pressing ESC has no effect,
Remarks
When you use a system-modal message box to indicate that the system is low on memory,the strings pointed to by the lpText and lpCaption parameters should not be taken from a resource file,because an attempt to load the resource may fail,
When an application calls MessageBox and specifies the MB_ICONHAND and MB_SYSTEMMODAL flags for the uType parameter,Windows displays the resulting message box regardless of available memory,When these flags are specified,Windows limits the length of the message box text to three lines,Windows does not automatically break the lines to fit in the message box,however,so the message string must contain carriage returns to break the lines at the appropriate places,
If you create a message box while a dialog box is present,use the handle of the dialog box as the hWnd parameter,The hWnd parameter should not identify a child window,such as a control in a dialog box,
Windows 95 only,The system can support a maximum of 16,364 window handles.
