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Fast Ensure Visible for CGridCtrl

, 5 Mar 2012 CPOL
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This tip shows a very fast algorithm (with some constraints enforced for it to work) to EnsureVisible a row in CGridCtrl by Chris Maunder

Introduction

 

In one of my projects, I had to load around 200000 rows in the CGridCtrl and then had to provide the functionalitiy of EnsureVisible to scroll to and highlight a row. So I had to come up with a reasonably fast algorithm. 

 

The code

 
// This function will only work if all the grid control rows are same in size

void GVEnsureVisible(CGridCtrl* pGridCtrl, int nRow)
{
	if(pGridCtrl== NULL)
		return;
 
	pGridCtrl->ResetScrollBars();
 
	int nItems = pGridCtrl->GetItemCount();
 
	int nPos = nRow;
 
	if(nItems > 0)
	{
		SCROLLINFO si;
 
		pGridCtrl->GetScrollInfo(SB_VERT, &si);
 
		double dx = (double)si.nMax / (double)nItems;
 
		si.cbSize = sizeof(SCROLLINFO);
 
		si.fMask = SIF_POS;
 
		si.nPos = (int)(dx * nPos) - si.nPage/2;
 
		pGridCtrl->SetScrollInfo(SB_VERT, &si, TRUE); 
		
	}
 
}
 

 

Points of Interest

 

This code will only work if all the rows of the Grid are of same size.

 

History

 

Article Uploaded : 5th March, 2012.

License

This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

Mukit, Ataul
Chief Technology Officer Rational Technologies
Bangladesh Bangladesh
C++ is not C with classes, JQuery is not Javascript, Google Search is not Learning, Design Patterns are not fashion, A code written in 2005 is not backdated just because it's 2015
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Comments and Discussions

 
QuestionCan you explain how this makes fast scroll? Also compare it with EnsureVisible, too. Pinmemberehaerim24-Oct-13 10:56 
AnswerRe: Can you explain how this makes fast scroll? Also compare it with EnsureVisible, too. PinmemberMukit, Ataul25-Oct-13 22:34 

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