KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q80553: ExpEdit.exe Changes Size of an Edit Control

Article: Q80553
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:3.1
Operating System(s): 
Keyword(s): kbfile kbsample kb16bitonly kbCtrl kbEditCtrl kbSDKPlatform kbGrpDSUser _IK
Last Modified: 05-DEC-1999

-------------------------------------------------------------------------------
The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
-------------------------------------------------------------------------------

SUMMARY
=======

ExpEdit.exe is a sample file that demonstrates how to change the size of an edit
control in response to an EN_UPDATE message. In the sample, when the typed text
reaches the end of a line, the edit control expands to allow the user to
continue typing on a new line.

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

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

ExpEdit.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.

Windows sends the EN_UPDATE notification message to the parent of the edit
control whenever the contents of the edit control have been altered, but before
the display is updated. The notification is sent to the parent window as the
HIWORD of the lParam parameter of a WM_COMMAND message. The ID of the control is
in the wParam.

Therefore, for an application to determine when it is necessary to change the
size of the edit control, it must handle the WM_COMMAND case in which the wParam
is the ID of the control and the HIWORD of the lParam is EN_UPDATE. When EXPEDIT
receives an EN_UPDATE notification message, it performs the following eight
actions:

1. Sends an EM_FMTLINES message to the edit control (wParam = 1). When the
  control processes this message, it modifies its buffer to have the character
  sequence carriage return-carriage return-linefeed (CR-CR-LF) at the end of
  each line.

2. Retrieves the length of the edit control's buffer.

3. Passes a handle to the (nonempty) buffer of the DrawText() function, which
  calculates the size of the rectangle required to hold all the text.

4. Adjusts the text height returned by DrawText because DrawText interprets the
  CR-CR-LF sequence at the end of each buffer line as two lines instead of one.

5. Compares the right edge of the rectangle returned from DrawText with the
  "limit." DrawText will extend the right edge of the rectangle if the text is
  too long. If the right edge of the last line exceeds the limit, then the edit
  control needs an additional line. EXPEDIT performs all the obvious limit
  checks.

6. If the height has not changed, then it is not necessary to change the size of
  the edit control, and EXPEDIT returns. Otherwise, the size of the edit
  control must be changed.

7. Updates the size of the edit control with MoveWindow() and UpdateWindow().

8. Returns FALSE so that the Dialog Manager will not do anything when it
  receives the EN_UPDATE message.

NOTE: The key idea of this implementation is to "predict" whether the next
character will fit in the edit control; if it will not, then add a new line to
the control so that the character will fit. This prediction is accomplished by
subtracting the width of "W" from the edge of the edit control's rectangle to
get the limit.

Additional query words:

======================================================================
Keywords          : kbfile kbsample kb16bitonly kbCtrl kbEditCtrl kbSDKPlatform kbGrpDSUser _IK 
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : WINDOWS:3.1
Issue type        : kbinfo

=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. SOME STATES DO NOT ALLOW THE EXCLUSION OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES SO THE FOREGOING LIMITATION MAY NOT APPLY.