Advanced Qt - A Deep Dive 2/6 Graphics View Part 2
summary
Custom QGraphicsItem must implement paint() and boundingRect(); shape() is optional but needed for precise hit tests. boundingRect() must be extremely cheap and minimal or performance and hover queries suffer; painting outside the reported rect produces graphical artifacts because QGraphicsView won’t repaint uncovered areas. Use flags like ItemIsMovable, ItemIsSelectable, and ItemSendsGeometryChanges and override itemChange to constrain movement. Collision helpers include collidesWithItem, collidingItems, and scene queries; scene.render can rasterize the whole scene but not conveniently a subtree.
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chapters (7)
- 0:00Introduction to custom items
- 1:51Implementing paint and bounding rect
- 7:15Shape and event handling
- 17:53Event handling levels
- 26:41Collision detection methods
- 28:45Graph visualization demo
- 36:26Summary and Q&A
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