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PageCounter Object for ScrollViews

  • April 16, 1999
  • By Volker Voecking
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Environment: The demo project was created with VC++ 6.0 SP1

When scrolling in a document that consists of quite a lot pages it might be helpful for the user to get an information which page of the document would be displayed if he/she >would release to slider of the scrollbar at a certain position.
Microsoft Word has such a feature. It's a tooltip-like window that displays the page number that corresponds to the current position of the slider during scrolling.

I implemented a class named CScrollViewPageCounter that displays such a page number in a window that looks like a tooltip-window. If you have a look at the source code you'll find out that it was quite easy to implement. The code itself is self-explanatory...

HOW TO USE

To use the ScrollViewPageCounter-Object you have to perform the following steps:

1. Add the files ScrollViewPageCounter.h and ScrollViewPageCounter.cpp to your project.

2. Add a new member m_pScrollViewPageCounter to your scroll view class.

 
CScrollViewPageCounter*
m_pScrollViewPageCounter;
Of course your have to include the corresponding header file here as well:

 #include "ScrollViewPageCounter.h"

3. Create the page counter object in CYourScrollView::OnInitialUpdate()

 
BOOL CYourScrollView::PreCreateWindow(CREATESTRUCT& cs)
{
 CScrollView::OnInitialUpdate();

 // Instantiate the counter object
 m_pScrollViewPageCounter = new CScrollViewPageCounter( this );
 }

4. Add a command handler for the message WM_VSCROLL:

 void CYourScrollView::OnVScroll(UINT SBCode, UINT nPos, CScrollBar* pScrollBar) 
{
 if ( nSBCode == SB_THUMBTRACK )
 {
  // calculate page number (insert your algorithm here)
 UINT uiPageNumber = (UINT) (nPos / 10) + 1;

  // display page number 
  m_pScrollViewPageCounter->DisplayPageNumber( uiPageNumber );
 }

 // when scrolling is finished we have to hide the page counter
 if ( nSBCode == SB_ENDSCROLL )
 m_pScrollViewPageCounter->Reset();
 
 CScrollView::OnVScroll(nSBCode, nPos, pScrollBar);
}
That's it.
Now compile and enjoy...

Download demo project - 33 KB

Download source - 3 KB

Date Last Updated: April 16, 1999






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