[KPhotoAlbum] Using STL-containers in kphotoalbum code ?

Jesper K. Pedersen blackie at blackie.dk
Tue May 1 10:56:36 CEST 2007


I agree that stl is everywhere.
I have no strong reasons against STL, except that it is one more thing to 
learn when programming Qt. (Actually I dont personally know much STL, so I 
would have a hard time with STL code).

Are you sure that QMap<ImageRequest*, whatever> doesn't do the job?

On Tuesday 01 May 2007 10:26, Henner Zeller wrote:
| Hi,
|
| I haven't seen any use of STL containers in the kphotoalbum code, so I
| was wondering if it was 'allowed' ? Are there reasons only to use the
| QT-containers ?
| (Yes, STL really is available everywhere!)
|
| The reasons why I am asking is because I need a set of elements, but
| don't want to store the values (unecessary call to the copy
| constructor), but only the pointers to it; the way you would do this
| using the STL would be to write a comparator that takes the pointers
| but compares the instances:
|
| struct FooPtrLessThan
| {
|   bool operator()(const Foo* a, const Foo *b) const
|   {
|     return *a < *b;
|   }
| };
|
| I don't see a way to do this with QMap or other containers in QT.
| Disclaimer: I haven't done any QT/KDE programming since KDE 1.1 so I
| might have missed something and happy to learn how this can be done
| using the existing containers.
|
| Reason for this all: There is a check in
| ImageManager::RequestQueue::addRequest() that looks if an ImageRequest
| to be added is already in the pending list. Since this is a linear
| search, adding n elements is an O(n^2) operation - which makes showing
| thumbnails on a big screen _very_ slow. Having the pending elements in
| a set with the values being compared would help a lot here.
|
| -henner
| _______________________________________________
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| KPhotoAlbum at kdab.net
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-- 
Having trouble finding a given image in your collection containing
thousands of images?

http://www.kphotoalbum.org might be the answer.


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