Q80946: RoEdit.exe Implements Read-Only Edit Control in Windows

Article: Q80946
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.0,3.1
Operating System(s): 
Keyword(s): kbfile kbsample kb16bitonly kbCtrl kbEditCtrl kbGrpDSUser kbOSWin310
Last Modified: 10-DEC-1999

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) versions 3.0, 3.1 
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SUMMARY
=======

In some situations, an application may contain text that is displayed for the
user to read, which is undesirable for the user to modify. The application can
use a static control to contain this text if the message is short. However, for
larger amounts of text, which require scrolling to display all the text in the
allotted area, something closer to an edit control is required. This article,
and its associated sample code, details how to make an edit control "read-
only."

MORE INFORMATION
================

The following files are available for download from the Microsoft Download
Center:

RoEdit.exe

For additional information about how to download Microsoft Support files, click
the article number below to view the article in the Microsoft Knowledge Base:

  Q119591 How to Obtain Microsoft Support Files from Online Services

Microsoft used the most current virus detection software available on the date of
posting to scan this file for viruses. Once posted, the file is housed on secure
servers that prevent any unauthorized changes to the file.


An application can create a read-only edit control by subclassing or
superclassing a standard edit control. The subclass procedure filters out
messages that change the contents of the edit control. The following code
fragment demonstrates this process:

     FARPROC gOldProc;
     LONG FAR PASCAL ROEditProc(HWND hWnd, WORD msg,

                                WORD wParam, LONG lParam)
     {
         switch (msg)
         {
             case WM_KEYUP:
             case WM_KEYDOWN:
             case WM_CHAR:
             case WM_CUT:
             case WM_COPY:
             case WM_PASTE:
             case WM_LBUTTONUP:
             case WM_LBUTTONDOWN:
             case WM_LBUTTONDBLCLK:
                 return 1L;
             case WM_GETDLGCODE:
                 return 0L;
         }
         return CallWindowProc(gOldProc, hWnd, msg, wParam, lParam);
     } //*** ROEditProc

In the example above, the subclass procedure traps mouse clicks, keystrokes, and
the cut, copy, and paste commands. It also traps the WM_GETDLGCODE message to
prevent an edit control in a dialog box from receiving the input focus.

The following example demonstrates superclassing an edit control to create a new
ROEDIT-class control that behaves similar to a read-only edit control. A ROEDIT
control implements the window procedure provided above. It also changes the
cursor to an arrow instead of an I-beam, which provides an additional indication
to the user that the contents of the control cannot be changed. Using an ROEDIT
control eliminates the necessity of subclassing each control after it is
created. When the application creates a control from the ROEDIT class, the
read-only behavior is provided automatically.

The following code demonstrates superclassing an edit control as described
above:

     FARPROC gOldProc;
     BOOL RegisterROEdit(HANDLE hInstance)
     {
         WNDCLASS wc;
         if (!GetClassInfo(NULL, "EDIT", &wc))
             return FALSE;
         gOldProc = (FARPROC)wc.lpfnWndProc;
         wc.style        &= ~CS_GLOBALCLASS;
         wc.lpfnWndProc   = ROEditProc;
         wc.hInstance     = hInstance;
         wc.hCursor       = LoadCursor(NULL, IDC_ARROW);
         wc.lpszClassName = "ROEDIT";

         return RegisterClass(&wc);
     } //*** RegisterROEdit

In Windows 3.1, there is a new style bit for the edit control (ES_READONLY) that
removes the editing capabilities of the edit control, leaving only the viewing
capabilities. This style is useful when the application shows the user a body of
static text that the user reads and does not modify.

Additional query words:

======================================================================
Keywords          : kbfile kbsample kb16bitonly kbCtrl kbEditCtrl kbGrpDSUser kbOSWin310 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK300 kbWinSDK310
Version           : WINDOWS:3.0,3.1

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