如何阻止JScrollPane中的滚动条更新？

Question

I have my own custom control inside JScrollPane . This is endless (in all directions) board with grid on it.

I have tried various approaches to implement it, including extending JViewport and adding by setViewport , and extending JComponent and adding by setViewportView .

All approaches cause some problems with endlessness and negative locations. Although component can freely draw itself in negative coordinates space, bad Swing API design doesn't not allow to transfer this information to container (only dimension is allowed, ie in positive direction).

Finally I came to conclusion, that if I totally break the channel which notifies JScrollPane about it's containment size, which updates scroll bars minimums and maximums, I will be allowed to set minimums and maximums by hand, which will solve the task.

So, this is the question: how to prevent custom component to notify JScrollPane about it's size? What is the simple way of such preventing?

Answer 1

I would rather separate logical (model) coordinates and component coordinates/size. Thus when user increases NORTH direction you should add appropriate change value to the component's height and shift rendering (or components) vertical location down.

As example I have a model element - Rectangle placed in (0,0). JPanel which paints the rectangle has initial paint point=(10,10). In fact when we paint we just g.translate(10,10) and then paint the model g.draw(myRectangle);

So when user increases NORTH (+10) we just increase the shift g.translate(10,10+10) and increase the JPanel's preferred height to reflect the size change in the JScrollPane .