Q87976: HOWTO: Creating a Foundation Classes Dialog Box with Custom Icon
Article: Q87976
Product(s): Microsoft C Compiler
Version(s): winnt:1.0,2.0,2.1
Operating System(s):
Keyword(s): kbDlg kbIcon kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC210 kbGrpDSMFCATL
Last Modified: 22-JUL-2001
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft C/C++ for MS-DOS, version 7.0
- Microsoft Visual C++ for Windows, 16-bit edition, versions 1.0, 1.5, 1.51, 1.52
- Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1
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SUMMARY
=======
Using the Microsoft Foundation Classes supplied with Microsoft C/C++ versions
7.0 and Microsoft Visual C++, you can create a main application window based on
a dialog box. However if a dialog is used as the application's main window, and
the dialog is created with a minimize button and then minimized, the default
application icon will be displayed. This article briefly describes two
approaches that can be taken to change the default icon to a custom
(application-defined) icon.
Starting with Visual C++ 4.0, AppWizard supports creation of dialog based
applications that have custom icons. The method described in this article works
with Visual C++ 4.0, but it is preferred to use the AppWizard generated code.
The CFormView class is a useful alternative to the "dialog as main window
technique" when using Microsoft Foundation Classes, and provides additional
features. For more information on CFormView, see the documentation supplied with
Microsoft Visual C++, the VIEWEX and CHKBOOK samples, and query on the following
words in the Microsoft Knowledge Base:
CFormView
A discussion of CFormView based applications is beyond the scope of this article.
MORE INFORMATION
================
One technique for using a dialog as the main window is documented in the "Class
Libraries User's Guide" which shipped with Microsoft C/C++ version 7.0 on page
334, and in both versions via the TRACER sample application. Neither of these
techniques illustrates how to change the default icon to a custom icon.
The first technique below, illustrated with code fragments, shows the
modifications required to allow the TRACER sample to display a custom icon when
minimized. This is the simplest approach to the problem.
The second technique is illustrated using a sample from the Software/Data
Library. While more complex, it illustrates how to use the Windows
::RegisterClass() API to register a class with an application defined icon.
Add OnPaint to CPromptDlg of the TRACER sample
----------------------------------------------
This technique will work for versions 1.0 and 2.0 of the Microsoft Foundation
Classes.
1. Add the following public declarations to the CPromptDlg class definition in
tracer.cpp:
afx_msg void OnPaint();
afx_msg BOOL OnEraseBkgnd(CDC* pDC);
afx_msg HCURSOR OnQueryDragIcon();
2. Add the following macros to the CPromptDlg message map in tracer.cpp:
ON_WM_PAINT()
ON_WM_ERASEBKGND()
ON_WM_QUERYDRAGICON()
3. Add the following function definitions in tracer.cpp:
void CPromptDlg::OnPaint()
{
CPaintDC dc(this); // device context for painting
if (IsIconic())
{
// Erase the icon background when placed over other app window
DefWindowProc(WM_ICONERASEBKGND, (WORD)dc.m_hDC, 0L);
// Center the icon
CRect rc;
GetClientRect(&rc);
rc.left = (rc.right - ::GetSystemMetrics(SM_CXICON)) >> 1;
rc.top = (rc.bottom - ::GetSystemMetrics(SM_CYICON)) >> 1;
// Draw the icon
HICON hIcon = AfxGetApp()->LoadIcon(AFX_IDI_STD_FRAME);
dc.DrawIcon(rc.left, rc.top, hIcon);
}
// Do not call CDialog::OnPaint() for painting messages
}
BOOL CPromptDlg::OnEraseBkgnd(CDC* pDC)
{
if (IsIconic())
return TRUE;
else
return CDialog::OnEraseBkgnd(pDC);
}
HCURSOR CPromptDlg::OnQueryDragIcon()
{
return AfxGetApp()->LoadIcon(AFX_IDI_STD_FRAME);
}
In this example, AFX_IDI_STD_FRAME is the ID of an icon contained in the
application's resource file, and the dialog template contains the
WS_MINIMIZEBOX style.
The PRIVDLG sample program from the Software/Data Library
---------------------------------------------------------
An example can be found in the Software/Data Library by searching on the word
PRIVDLG, the Q number of this article, or S13583. PRIVDLG was archived using the
PKware file-compression utility.
If you are creating a standard frame window, the only step required for your
application to use a custom icon is to define an icon resource in your .RC file
with the constant AFX_IDI_STD_FRAME. When the Microsoft Foundation Classes
libraries register the window class for your frame window, they will use this
icon as the window icon.
Alternatively, if your application uses a dialog box as its main window, the
procedure for using a custom icon is a bit more involved. The main reason you
can't simply use AFX_IDI_STD_FRAME for MFC 1.0 or IDR_MAINFRAME for MFC 2.0 and
MFC 2.5 is that all Windows dialog boxes use a pre-registered window class, and
the icon used for this class cannot be changed easily.
The solution is to register a private window class to be used for your dialog
box. Because the name of this window class must be specified in the dialog
template, the Microsoft Foundation Classes function AfxRegisterWndClass will not
work, because it creates a new class name dynamically at run time.
The restrictions on registering your own private dialog class in Microsoft
Foundation Classes are the same as in standard C Windows programming. For more
information, query on the following words in the Microsoft Knowledge Base:
private and dialog and class
To register a private dialog class with a custom icon, do the following three
steps:
1. Register a new private dialog class using the ::RegisterClass() function with
a unique class name. Fill in your own icon for the hIcon field of the
WNDCLASS structure, and add your custom icon to the .RC file. This class
should only be registered once for your application. Be sure to follow the
standard Windows rules for registering a private dialog class (see the
Knowledge Base reference above).
2. Add the CLASS "classname" directive to your dialog box resource file, using
the unique class name you registered in step 1. Make sure your dialog
contains the WS_MINIMIZEBOX style bit if you want to allow the dialog to be
minimized.
3. Create a dialog using the template from step 2.
Additional query words: kbinf 7.00 1.00 1.50 2.00 2.50 2.51 2.52
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Keywords : kbDlg kbIcon kbMFC KbUIDesign kbVC100 kbVC150 kbVC200 kbVC210 kbGrpDSMFCATL
Technology : kbAudDeveloper kbMFC
Version : winnt:1.0,2.0,2.1
Issue type : kbhowto
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