How are QPen and QBrush expencive?

[Dmitriano]

Do QPen or QBrush contain some OpenGL resources?

Does it make a sense to create them once before setting them in a loop?

Can I do this

painter->setPen(QPen(QColorConstants::Green));

?

[Christian Ehrlicher]

Every allocation which you can avoid makes sense.

[Dmitriano]

@Christian-Ehrlicher do they really allocate some resources? Or they are some structure like

struct Brush { QColor color; ... };

[Christian Ehrlicher]

@Dmitriano QPen and QBrush are classes as described in the documentation.

[JonB]

@Dmitriano
In addition to @Christian-Ehrlicher: don't forget that both of these are shared instance data, as per many Qt classes in https://doc.qt.io/qt-5/shared.html, so memory/resource usage may be less than you think.