Microsoft KB Archive/140722

{|
 * width="100%"|

PRB: Cannot Center Explorer-Style FileOpen Common Dialog Box

 * }

Q140722

-

The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK)

-

SYMPTOMS
Generally, an application that attempts to alter the default behavior of a dialog box before it even comes up on the screen, would process the WM_INITDIALOG message. For common dialogs, this message is processed in the common dialog's hook procedure. However, attempting to center the new Explorer-Style FileOpen Common Dialog in Windows 95 in the hook procedure's WM_INITDIALOG case will result in an off-center dialog box.

CAUSE
This problem arises with the new Explorer-Style common dialog only when the OFN_ENABLETEMPLATE flag is set in the OPENFILENAME structure, and a dialog template is specified in lpTemplateName that includes the new controls that you want to add to the dialog box.

Typically, the code to center a dialog box would first get the dimensions of the dialog box by using GetWindowRect so it could be centered on the screen appropriately. At WM_INITDIALOG time, the FileOpen dialog has not been resized to accomodate the new controls specified in the lpTemplateName member of the OPENFILENAME struct; therefore, GetWindowRect returns the dimensions of the original FileOpen dialog, not that of the actual customized dialog that comes up on the screen. This then causes the dialog box to come up a few pixels off-center.

RESOLUTION
Call GetWindowRect and the rest of the code to center the dialog box, in the hook procedure's WM_NOTIFY case, with code set to CDN_INITDONE, a new common dialog notification code for Windows 95. By this time, all the controls have been added in, and the dialog has been resized accordingly.

STATUS
This behavior is by design.

MORE INFORMATION
Here's how the Win32 SDK COMDLG32 sample can be modified to do this. Note that COMMDLG creates the dialog specified by lpTemplateName as a child of the standard FileOpen common dialog box. As a result, the hDlg passed to the application's hook function will be the child of the standard FileOpen dialog box. To get a handle to the standard dialog box from the hook function, an application needs to call GetParent (hDlg).

Code Sample Modification of Win32 SDK COMDLG32 Sample
  BOOL NEAR PASCAL TestNotify(HWND hDlg, LPOFNOTIFY pofn) {   switch (pofn->hdr.code) {

case CDN_INITDONE: {          CenterWindow (GetParent (hDlg), NULL); break; }



// Center with respect to another window. // Specifying NULL for hwndParent centers hwndChild relative to the // screen. BOOL CenterWindow(HWND hwndChild, HWND hwndParent) {      RECT    rcChild, rcParent; int    cxChild, cyChild, cxParent, cyParent; int    cxScreen, cyScreen, xNew, yNew; HDC    hdc;

// Get the Height and Width of the child window. GetWindowRect(hwndChild, &rcChild); cxChild = rcChild.right - rcChild.left; cyChild = rcChild.bottom - rcChild.top;

if (hwndParent) {      // Get the Height and Width of the parent window. GetWindowRect(hwndParent, &rcParent); cxParent = rcParent.right - rcParent.left; cyParent = rcParent.bottom - rcParent.top; }

else {         cxParent = GetSystemMetrics (SM_CXSCREEN); cyParent = GetSystemMetrics (SM_CYSCREEN); rcParent.left = 0; rcParent.top = 0; rcParent.right = cxParent; rcParent.bottom= cyParent; }

// Get the display limits. hdc = GetDC(hwndChild); cxScreen = GetDeviceCaps(hdc, HORZRES); cyScreen = GetDeviceCaps(hdc, VERTRES); ReleaseDC(hwndChild, hdc);

// Calculate new X position, then adjust for screen. xNew = rcParent.left + ((cxParent - cxChild) / 2); if (xNew < 0) {          xNew = 0; }      else if ((xNew + cxChild) > cxScreen) {          xNew = cxScreen - cxChild; }

// Calculate new Y position, then adjust for screen. yNew = rcParent.top + ((cyParent - cyChild) / 2); if (yNew < 0) {          yNew = 0; }      else if ((yNew + cyChild) > cyScreen) {          yNew = cyScreen - cyChild; }

// Set it, and return. return SetWindowPos(hwndChild,                          NULL,                           xNew, yNew,                           0, 0,                           SWP_NOSIZE | SWP_NOZORDER); } Additional query words:

Keywords : _IK kbCmnDlg kbCmnDlgFileO kbCmnDlgSave kbOSWinNT400 kbOSWin2000 kbSDKWin32 kbGrpDSUser kbOSWin95 kbOSWin98

Issue type : kbprb

Technology : kbWin32SDKSearch kbAudDeveloper kbSDKSearch kbWin32sSearch