Re: Quartz anti-aliasing scrollview issue.

Humn, no matter what I tried I couldn't fix it.

I have however come up with a solution that seems to work. In my view I override adjustScroll

- (NSRect)adjustScroll:(NSRect)proposedVisibleRect

{

NSRect modifiedRect=proposedVisibleRect;

modifiedRect.origin.x = (int)(modifiedRect.origin.x/2) * 2;

modifiedRect.origin.y = (int)(modifiedRect.origin.y/2) * 2;

return modifiedRect;

}

To scroll a minimum of 2 pixels, this seems to solve the problem.

This works in my single simple line case and also in my other test code which is drawing the type of data that the final application will be drawing.

Quartz looks beautiful. Even comparing my basic simple app with our current shipping product on windows shows a marked difference in quality.

If this fix works (which as far as I can tell it does) then I can live with a minimum scroll of 2 pixels.

Adrian

On 17 Mar 2008, at 05:33, mikevann wrote:

One more thought, constrain your stroked line to just the drawn rect. If you're using copy-on-scroll you'll be stroking over the copied area.

On Mar 16, 2008, at 4:55 PM, Adrian Carpenter wrote:

Hi,

I'm currently doing some groundwork for some future developments. I have a need to draw large amounts 2d vector graphic data.

For various reasons (cross platform, different "targets" on the same platform etc), I wrap quartz up in C++ layer.

As a test, I'm using a simple subclassed NSView embedded in a scrollview, this is my drawRect from the custom class.

- (void)drawRect:(NSRect)rect
{
CGContextRef myContext = (CGContextRef) [[NSGraphicsContext currentContext] graphicsPort];

CGContextSetRGBFillColor(myContext, 1, 1, 1, 1);

CGContextFillRect(myContext, CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, rect.size.height));

CGContextSetRGBFillColor(myContext, 1, 1, 0, 0.5);

CGContextFillRect(myContext, CGRectMake(rect.origin.x, rect.origin.y, rect.size.width, rect.size.height));

CGContextSetRGBStrokeColor(myContext, 0, 0, 0, 1);

CGContextMoveToPoint(myContext, 300, 40);
CGContextAddLineToPoint(myContext, 600, 40);

CGContextStrokePath(myContext);
}

Now the problem that I am experiencing is that when I scroll using the trackpad on my powerbook, the area that scrolls in is solid black, the "anti aliasing" appears to be saturating.

However, scrolling using the actual scrollbars or the arrows does not exhibit the same problem, presumably because the area being scrolled in is much larger.

setting copiesOnScroll to NO "fixes" the problem as this obviously causes a refresh of the entire visible rectangle rather than a copybits and redraw of a small amount of area.

Disabling anti-aliasing also fixes the problem, this is not an option though!

Does anybody have a nicer solution or workaround this problem? I'm guessing that the actual problem is due to the invalid region being non-integer, but I can't quite put my finger on it because (and this is from a windows software background) I'm drawing both the background and foreground.

Any ideas!?