How is a rounded rect view with transparency done on iphone?

Question

A lot of apps pop up a transparent view with rounded corners and an activityIndicator when running a time consuming operation.

How is this rounding done and is it po

Answer 1

I abstracted out @lostInTransit's response into this function:

static void ContextAddRoundedRect(CGContextRef c, CGRect rect, CGFloat radius) {
  CGFloat minX = CGRectGetMinX(rect);
  CGFloat maxX = CGRectGetMaxX(rect);
  CGFloat minY = CGRectGetMinY(rect);
  CGFloat maxY = CGRectGetMaxY(rect);

  CGContextMoveToPoint(c, minX + radius, minY);
  CGContextAddArcToPoint(c, maxX, minY, maxX, minY + radius, radius);
  CGContextAddArcToPoint(c, maxX, maxY, maxX - radius, maxY, radius);
  CGContextAddArcToPoint(c, minX, maxY, minX, maxY - radius, radius);
  CGContextAddArcToPoint(c, minX, minY, minX + radius, minY, radius);
}

which places the path onto the context for you to do with as you may

slightly different CoreGraphics calls and i didn't close the path, in case you want to add that

CGContextFillPath(c);