BUG: Print Preview Scroll Bar Disappears after Zoom In, Zoom Out

ID: Q189580

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1, 4.2, 5.0

SYMPTOMS

In MFC's Print Preview, there is a toolbar that contains zoom-in and zoom- out buttons, and there may be a vertical scroll bar. The scroll bar allows the user to scroll within a page when zoomed in, or it can be used to move between pages when zoomed out. When completely zoomed out, the arrow buttons on the scroll bar allow the user to move from one page to another. If the user presses the zoom-in button, and then zooms out completely, the scroll bar disappears and does not reappear until the user exits Print Preview and starts it up again from the menu.

CAUSE

The scroll bars are not being re-enabled after zooming out.

RESOLUTION

There is no easy workaround, but an approximate workaround below allows the user to scroll through pages using the up/down arrows of the scroll bars, but the "thumbs" will not appear proportionally.

Derive a class from CPreviewView (you need to include Afxpriv.h) and override PositionPage(). You can use code similar to the following:

Sample Code


   //MyPreviewView.h

   #include <afxpriv.h>

   class CMyPreviewView : public CPreviewView
   {

   private:
      DECLARE_DYNCREATE(CMyPreviewView)

   protected:
      virtual void PositionPage(UINT nPage);
   };

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

   //MyPreviewView.cpp
   #include "stdafx.h"
   #include "MyPreviewView.h"

   IMPLEMENT_DYNCREATE(CMyPreviewView, CPreviewView )

   /////////////////////////////////////////////////////////////////// 
   void  CMyPreviewView::PositionPage(UINT nPage)
   {
      CPreviewView::PositionPage(nPage);

      if(m_nZoomState == ZOOM_OUT)
         EnableScrollBarCtrl(SB_VERT, TRUE);
   }
   ================================================================

Add OnFilePrintPreview() to your application's view class, and put your CPreviewView-derived class name in the call to DoPrintPreview:

Sample Code


   void CScribbleView::OnFilePrintPreview()
   {
      // In derived classes, implement special window handling here.
      // Be sure to Unhook Frame Window close if hooked.
      // Must not create this on the frame. Must outlive this function.

      CPrintPreviewState* pState = new CPrintPreviewState;

      // DoPrintPreview's return value does not necessarily indicate that
      // Print Preview succeeded or failed, but rather what actions are
      // necessary at this point. If DoPrintPreview returns TRUE, it means
      // that OnEndPrintPreview will be (or has already been) called and
      // the pState structure will be/has been deleted.
      // If DoPrintPreview returns FALSE, it means that OnEndPrintPreview
      // WILL NOT be called and that cleanup, including deleting pState,
      // must be done here.

      if (!DoPrintPreview(AFX_IDD_PREVIEW_TOOLBAR, this,
         RUNTIME_CLASS(CMyPreviewView), pState))
      {
         // In derived classes, reverse special window handling here for
         // Preview failure case.

         TRACE0("Error: DoPrintPreview failed.\n");
         AfxMessageBox(AFX_IDP_COMMAND_FAILURE);
         delete pState; // Preview failed to initialize, delete State now.
      }
   }
   ==============================================================

Change your view's message map so that it has OnFilePrintPreview() in it:


   ON_COMMAND(ID_FILE_PRINT_PREVIEW, OnFilePrintPreview)

Add the appropriate #include to your applications's view class, such as:


   #include "MyPreviewView.h"

Add the following line to your view class's header file:


   void OnFilePrintPreview();

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

To reproduce this behavior:

Run the SCRIBBLE sample application (specifically, step 7). (From the Visual C++ Help menu, click Search, and type "scribble" in the Index Tab of the Search dialog box.)

Draw a scribble in the view.

On the File menu, click Print Preview. Notice that there is a vertical scroll bar that allows you to go through the pages.

Select "Zoom in" from the toolbar.

Select "Zoom out" from the toolbar. Notice that the vertical scroll bar no longer exists.

REFERENCES

For more information on Print Preview, see the MFC Technote in the Visual C++ documentation:

TN030: "Customizing Printing and Print Preview"

Additional query words: scrollbar kbprinting kbmfc400bug kbmfc410bug kbmfc420bug kbmfc500bug


Keywords          : 
Version           : WINNT:4.0,4.1,4.2,5.0
Platform          : winnt 
Issue type        : kbbug

Last Reviewed: August 2, 1999