iOS: how to change the size of the UIScrollView content?

Question

I\'m now trying to create my own Text panel (with code highlighting and so on).

In fact everything is ready except one thing - scrolling

What I\'ve done: created

Answer 1

Part 1:

The scroll view's content size is not actually related to the size or position of the views it contains. If you want to change the size of the content view as well as the scroll view's content, you need to call two different methods.

CGSize newSize;
UIScrollView *scrollView;
// assume self is the content view
CGRect newFrame = (CGRect){CGPointZero,newSize}; // Assuming you want to start at the top-left corner of the scroll view. Change CGPointZero as appropriate
[scrollView setContentSize:newSize]; // Change scroll view's content size
[self setFrame:newFrame]; // Change views actual size

Part 2:

setNeedsDisplay marks the entire view as needing display. To cause it to display only the visible part, you need to use setNeedsDisplayInRect:visibleRect.
Assuming the view is at the top-left corner (its frame's origin is 0) and the scroll view does not allow zooming, the visible rect can be found using the scroll view's content offset and bounds size.

CGRect visibleRect;
visibleRect.origin = [scrollView contentOffset];
visibleRect.size = [scrollView bounds].size;
[self setNeedsDisplayInRect:visibleRect];

You could also choose to draw a part of the visible rect if only part changes.