Vertical Text Centering in an Edit Control

I have come across many posts asking about the ability to center text vertically in a simple, single-line edit control. Therefore, I decided to sit down and write a code that demonstrates how to achieve this. I have used a WM_NCCALCSIZE message to adjust the NC area.

Because a control in a dialog is subclassed, all messages needed to create a window and calculate window areas were already handled before subclassing occurs. To force the WM_NCCALCSIZE NC area, I decided to call SetWindowPos once, from the WM_CTLCOLOR reflection message handler (WM_CTLCOLOR_REFLECT) to establish new NC area dimensions.

WM_CTLCOLOR is received by the control after subclassing, before the control is visible. You can use any other message handler to call SetWindowPos; make sure it occurs before the control is shown. Of course, because the NC area has changed, I had to handle WM_NCPAINT to paint a new NC area that the edit control does not handle because it has no idea about its existence whatsoever.

For that, I have added two member variables of the CRect type that hold calculated bottom and top rectangles of the new NC area after calculating the client area height that is needed to accommodate the font. Computation of the new NC is handled in the WM_NCCALCSIZE handler. Because the control is not resized, this computation has to be performed once only. In WM_NCPAINT, I simply use rectangles to tell DC what to fill with a color of the default system brush, so be careful when changing background color.

To use this class:

1. Copy the CVEdit header and implementation file to your project directory (or central repository of your custom classes).
2. Include both files in a project. Delete the .clw file and invoke a class wizard to re-create it.
3. In the dialog containing the edit control, use the wizard to subclass the control (add member variable). Make sure you choose the control type and CVEdit class from the combo.

THIS CODE IS DESIGNED TO WORK WITH A SINGLE-LINE EDIT CONTROL. It just illustrates how to use WM_NCCALCSIZE to adjust the vertical margins of the edit control. Modify it to your needs.