CODEWITHSUNDEEP
c++qtqgraphicsitem
Dejwi
Dejwi

Reputation: 4497

Draw border of QGraphicsItem

How to draw border of QGraphicsItem ? Simple painter->drawRect( boundingRect() ) in overloaded paint method is not correct(bottom-right corner is outside the item).

Upvotes: 2

Views: 6561

Answers (4)

Arnold Spence
Arnold Spence

Reputation: 22292

The coordinate system for graphics and drawing shapes can be tricky to get straight. You will often find yourself programming test drawings to get it right but it is drawing precisely what you are telling it to draw. You need to understand the coordinate system. On this page, pay particular attention to the picture of "One pixel wide pen" for QRectF.

Upvotes: 4

Kaleb Pederson
Kaleb Pederson

Reputation: 46509

Note that the docs for QPainter::drawRect() mention the actual width:

A filled rectangle has a size of rectangle.size(). A stroked rectangle has a size of rectangle.size() plus the pen width.

Given that, I'd imagine you'd want something slightly more complicated than just using the bounding rectangle:

QRect r = boundingRect();
QPen p = painter->pen();
painter->drawRect(QRect(r.x(), r.y(), r.width()-p.width(), r.height()-p.width()));

Upvotes: 4

Jakub Wieczorek
Jakub Wieczorek

Reputation: 1919

QGraphicsEffect may be your friend here. You can subclass it to draw a border around an arbitrary QGraphicsItem. Just remember to reimplement boundingRectFor() to include the extra border.

Upvotes: 2

Dejwi
Dejwi

Reputation: 4497

I found out my problem. Thanks for all advises, but now I see, that my problem was elsewhere.

I can draw a QRectF(), which fits to boundingRect of my item, but... when I scale my QGraphicsView (no matter if I use fitInView() method, or my own implementation) there are some errors in displaying my border.

Rarely one or two lines of rect are tighter then others. I think that it can be be related to my QGraphicsItems, which are also QGraphicsSvgItems at once.

Upvotes: 0

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