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Hey guys,
I am using a CListBoxEBX control from this project, DrawItem function is overriden.
http://www.codeguru.com/cpp/controls...cle.php/c4745/
When I fill this list box intensively with lots of items per second i see a lot of
flickering.
What are usual techniques in GDI area to reduce flickering as much as possible?
thanks
One common technique is Double Buffering. You should find a lot of material on the Internet regarding this topic.
For controls like the Listbox, you can suspend updates while making multiple changes. I haven't tested this myself, but CWnd::LockWindowUpdate() and CWnd:UnlockWindowUpdate() seem to be what you're looking for. I'd be curious if this worked for you.
In .NET-land, you would use SuspendLayout() and ResumeLayout(), but there doesn't seem to be an equivalent in MFC.
Double Buffering of what, PadexArt?Quote:
Originally Posted by PadexArt
You might want to try CWnd::SetRedraw ().
yes, before updating the list (either removal or adding an item) I disable redrawing and enable it afterQuote:
Originally Posted by Mike Harnad
double buffering of your drawings. ..Quote:
Originally Posted by nazgul27
First do all the drawings to a temp buffer. . and then. . write the tempbuffer to the DC. Result : no more filckering.
Double buffering (or rather, offscreen drawing - double buffering is something else, strictly speaking ;) ) would be overkill in this case, and totally unnecessary.
Like Mike said: Call SetRedraw(false) before inserting / removing items, and SetRedraw(true), follwed by Invalidate(), after you're done with your bulk item operation.
Some form of optimizied drawing should be employed to ensure flickering is not affecting other operations ( such as scrolling). In some cases it is desirable to see something is happening but with a minimal flicker and SetRedraw cannot help there.
Have you tried using int InitStorage( int nItems, UINT nBytes ) with the number of items to speed up the loading process.
actually there is no bulk operation. The items are inserted on run time one by one. But there are times when the number of those items is huge, about 100 items per second.Quote:
Originally Posted by gstercken
This control is a self redrawing control. Before any Remove/Add operation I disable redraw and enable it after but it does not help.
When I added OnEraseBackground handler and return FALSE from there the flickering is gone. but the only disadvantage is when the listbox is not full the background is not invalidated in case it's overlapped with something but it's not that nasty since the control gets filled pretty quickly
Did you try my above suggestion ??
if the number of items is not know before their insertion, he cannot use InitStorage.Quote:
Originally Posted by Vanaj
When an item is inserted, disable Redraw, and start a timer (restart timer if already started). When timer expires, enable re-draw and invalidate. A timer of about 0.75 seconds is what I like.Quote:
The items are inserted on run time one by one. But there are times when the number of those items is huge, about 100 items per second.
No "flicker" but fairly quick updates :D :D :D
One can make an educated guess...but he has not said this value is unknown and anything greater than 100 WILL help and 500 is better even if only 150 is loaded. Mine loads 4,000+ with NO flicker and InitStorage() is run before loading using values from database returns.Quote:
Originally Posted by Alin
Quote:
Originally Posted by Vanaj
this means that he does not know the number of items he's gonna have, or so i understand...Quote:
Originally Posted by nazgul27