?
Solved

Drag & Drop in a CScrollView

Posted on 1998-07-04
1
Medium Priority
?
394 Views
Last Modified: 2013-11-20
I'm implementing my own drag and drop of bitmaps in a CScrollView window. Right now I redraw the entire view for each movement, but this is not a good solution since I'm going to have quite a lot of graphics in this window. What is the most efficient way to do this? Can I somehow read a section of the view into memory, draw my bitmap there, and the next time redraw only that section and so on.
0
Comment
Question by:zingo
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
1 Comment
 
LVL 3

Accepted Solution

by:
eugenem earned 300 total points
ID: 1318732
First thing you need is clipping. This means you need to repaint only what you need, not the whole view. For example, when you drag a bitmap, you take previous rectangle of the bitmap and current rectangle of bitmap and compute the smallest rectangle that contains both of these. Then you set this rectangle as a clipping rectangle and draw your view. It will automatically prevent any output to any place of your DC outside this rectangle.
To set clipping rectangle you can use
void CWnd::InvalidateRect( LPCRECT lpRect, BOOL bErase = TRUE );
If you want to get this rectangle from OnPaint, use
CPaintDC dc( this );
CRect rectUpdate;
dc.GetClipBox(&rectUpdate);

If you want some more serious clipping you can use CDC::SelectClipRgn. You should also look for CRgn.

0

Featured Post

VIDEO: THE CONCERTO CLOUD FOR HEALTHCARE

Modern healthcare requires a modern cloud. View this brief video to understand how the Concerto Cloud for Healthcare can help your organization.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction: Dynamic window placements and drawing on a form, simple usage of windows registry as a storage place for information. Continuing from the first article about sudoku.  There we have designed the application and put a lot of user int…
Introduction: Dialogs (1) modal - maintaining the database. Continuing from the ninth article about sudoku.   You might have heard of modal and modeless dialogs.  Here with this Sudoku application will we use one of each type: a modal dialog …
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
Suggested Courses

801 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question